The anti‐Trypanosoma activities of medicinal plants: A systematic review of the literature

Abstract

Background

The existing drug treatments for trypanosomiases are limited and suffer from shortcomings due to their toxicity and the emergence of resistant parasites. Developing anti‐trypanosomal compounds based on natural products is a promising way of fighting trypanosomiases.

Objectives

This study aims to identify through scientific review a large variety of medicinal plants (anti‐trypanosomal) used worldwide and scientifically shown to display anti‐trypanosomal effects.

Methods

To collect data, the anti‐trypanosomal activities of Africa, Asia, the Middle East, South America, North America, Europe and Oceania medicinal plants have been checked by considering the published paper.

Results

Based on collected data, 77 natural molecules were reported in the literature. Of which 59 were from the African region, 11 from Asia, 3 from Europe and 4 from Latin America. These active components belong to alkaloids, triterpenoids, lactone, quinoids, flavonoids, iridoids, lignans, steroids, lipids, oxygenated heterocycles, benzenoids, proteins, coumarins, phenylpropanoids and peptides. We also specified the prosperous plants with unique anti‐trypanosomal activities.

Conclusions

However, there is a need for further studies on the ability of the isolated compounds to ameliorate the trypanosome‐induced pathological alterations and also the elucidation of their modes of actions and activities against other trypanosome species.

1. INTRODUCTION

Trypanosomiases are a widespread vector‐borne disease globally that affects humans and domestic and wild animals. The pathophysiology of these diseases may vary depending on the pathogenic species involved and the host. Its symptoms in humans include irregular fever and septicemia. At the same time, in animals, a decrease in the number of red blood cells and body mass can lead to unproductivity and death (Osório et al., 2008). Trypanosomiases have been considered a significant public health problem in animals and humans (Hassan et al., 2020).

The global prevalence of trypanosomiases, in general, is underreported (Wilkinson and Kelly, 2009). The two significant trypanosomiases in humans are the African Trypanosomiases (HAT, also known as sleeping sickness) and Chagas disease, caused by Trypanosoma brucei and Trypanosoma cruzi. According to the World Health Organization (PAHO, 2016) data, T. cruzi infects about 5–6 million people worldwide and causes approximately 10,000 deaths per year (WHO, 2015). For HAT, its incidence is now at a historic low, with fewer than 1000 cases reported in 2018 (WHO, 2018).

A small number of trypanocidal drugs have shown efficacy against the two species of parasites. These include two approved drugs that can treat Chagas Disease during its acute phase (Benznidazole and Nifurtimox) (Sepúlveda‐Robles et al., 2019). The recommended drugs to treat the HAT include suramin (EC: 205‐658‐4), pentamidine (EC: 205‐424‐1), melarsoprol (EC: 207‐793‐4) and Fexinidazole Winthrop (Dickie et al., 2020). Fexinidazole is a DNA synthesis inhibitor for the Neglected Diseases initiative (DNDi) for the oral treatment of HAT and Chagas’ disease, which shows activity against Trypanosoma brucei gambiense and T. b. rhodesiense as well as preceeds through Phase II clinical trial based on FDA definition (Deeks, 2019). The other drugs, including Nifurtimox, are in Phase III clinical trials, and Eflornithine (EC: 205‐658‐4) has not yet entered into clinical trial stages. However, the first three drugs have limitations, including poor efficacy, potential adverse effects and the development of resistance by the parasites (Wilkinson and Kelly, 2009). Oral fexinidazole is a valuable first‐line treatment option in the early stages of (stage 1 or early stage 2) African Trypanosoma brucei gambiense (Kande Betu Ku Mesu et al., 2021). Eflornithine is a standard treatment for second‐stage therapy, and nifurtimox‐eflornithine combination therapy is a proper combination for first‐line use in HAT control programs (Priotto et al., 2009). Additionally, DNDi has developed another oral therapy, acoziborole, suitable for the treatment of both stage 1 and stage 2 disease in a single dose (Dickie et al., 2020).

Also, the neglected disease status means a little economic benefit for developing novel drugs in this field (Dickie et al., 2020). There is little interest in developing drugs against these diseases because they are neglected. However, they are called ‘neglected diseases’ because pharmaceutical companies have little interest in investing in them, as fexinidazole has recently met that need for T. brucei gambiense (Kande Betu Ku Mesu et al., 2021). However, melarsoprol is very toxic and is still being used against T. brucei rhodesiense (Fairlamb and Horn, 2018), and resistance may still arise against fexinidazole, so new lead compounds for drugs against these parasites remain essential.  Thus, there has been a considerable need to find new trypanocidal agents with better efficacy and safety profiles.

Natural products are valuable sources for discovering and developing effective medicines against various diseases (Hashemi et al., 2021; Newman and Cragg, 2016; Nezaratizade et al., 2021; Tajbakhsh et al., 2021a; Tajbakhsh et al., 2021b). The WHO report highlighted that a quarter of currently useful drugs had been derived from traditional plants. For many parts of the world, especially where trypanosomiases are prevalent in Africa, India, China, the Middle East and South Asia, traditional medicines with local preparations are the predominant means of therapy (Ahmad Khan and Ahmad, 2019). These countries are also endowed with tremendous medicinal plant resources, some of which have shown efficacy under in vitro and/or in vivo conditions. At present, the available reviews in this field report anti‐trypanosomal activity for particular regions, such as the African region (Ibrahim et al., 2014; Lawal et al., 2015), Myanmar (Asia) (Bawm, 2010) and Saudi Arabia (Al‐Musayeib et al., 2012). These exciting but somehow dated but interesting publications reported a lot of medicinal plants and some isolated active compounds. Finally, the current, up‐to‐date review covers natural products isolated from plants used worldwide and active against trypanosomiases.

1.1. Ethnopharmacology of anti‐trypanosomal medicinal plants in Africa continent

Since the primitive period, herbs have been a valuable source of medication for both human and livestock diseases (Odhiambo et al., 2011). During these thousand years of observation, it has been found that different parts of herbs possess healing properties. With the advancement in pharmaceutical and medical sciences, phytoconstituents were subsequently confirmed to be accountable for the curative characteristics of plants. Nowadays, high‐tech methods have resulted in the isolation and elucidation of these phytoconstituents. Some of these phytoconstituents have served as lead compounds to develop chemotherapeutic drugs against diseases, whether infectious or non‐infectious (Kasilo et al., 2010).

On the one hand, some modern drugs have their ethnopharmacological sources. Nevertheless, despite technological advances, the discovery of new drugs faces a primary innovation deficit that unfavourably impacts the pharmaceutical industry. On the other hand, current studies demonstrate that entry barriers have decreased for introducing a new drug (DiMasi & Paquette, 2004; Patwardhan, 2005).  Seventy‐five per cent of the approved anti‐infectious disease drugs from 1981 to 2002 are natural origins (Newman et al., 2003), while 61% of all new chemical compounds presented as drugs during the same period could be considered natural products (Gupta et al., 2005).

Aside from this significant role of medicinal herbs in drug discovery, the use of local herbal products provides the only option for therapeutic purposes for African populations. The primary reason for this issue is the lack of a sound health care system in some parts of the continent, which causes the population's vulnerability to many infectious diseases (Elujoba et al., 2005). Eighty per cent of the African population depends almost entirely on herbal medicinal products for their primitive health care needs (Kasilo et al., 2010).

One of the significant infections that severely affect humans and animals in Africa is African trypanosomiasis, also called ‘sleeping sickness’ in humans or ‘Nagana’ in animals. (Atawodi 2005; Welburn et al., 2009). It is one of the most neglected parasitic diseases that affect human health and dramatically reduces Africa's livestock productivity (Atawodi 2005; Welburn et al., 2009). Preliminary estimates show that almost 70 million people distributed over 1.55 million km² in Africa are at risk of this infectious disease (Simarro et al., 2012). In addition, animal trypanosomiases, or Nagana, are distributed over nearly 25 million km² in Africa, where livestock productivity fell by 50%. The important species in this disease include Trypanosoma vivax, Trypanosoma congolense, Trypanosoma evansi  and  Trypanosoma brucei (Mbaya et al., 2009). Currently, the African trypanosomiases chemotherapy remains abandoned due to the available approved drugs with some concerns, including parasite resistance, toxicity, poor availability, high cost and parenteral root of administration (Ibrahim et al., 2014). Fortunately, the continent has vast resources of medicinal plants that are traditionally used to cure this disease. This is evident in the tendency to use ethnobotanical science to manage disease in different parts of Africa (Atawodi et al., 2002; Ntie‐Kang et al., 2013). It is important to note that studies have confirmed the impact of these African herbal remedies as anti‐trypanosomal agents under in vitro and/or in vivo models. Hence, a critical review of these studies (anti‐trypanosomal) African medicinal plants in the African continent and anti‐trypanosomal plants in other continents is required to provide a comprehensive record to specify gaps in knowledge about the basic strategies to address such gaps.

2. MATERIALS AND METHODS

2.1. Search strategy

Literature about medicinal plants (with anti‐trypanosomal activity) was collected online from published articles using the keywords: ‘Trypanosoma AND medicinal plant’, ‘Trypanosoma AND natural product’ from 1960 to May 2020. These keywords were entered into the primary scientific databases, such as PubMed, Science Direct, Scopus and Google scholar. The articles obtained were included based on the reliability of their source. Some articles were found by examining the bibliography of other publications or by directly accessing the webpage of the journal.

2.2. Inclusion and exclusion criteria

The documents used were selected based on several criteria: (a) they have published articles or doctoral theses, (b) research has been carried out on antiparasitic medicinal plants in general and anti‐trypanosomal plants in particular, (c) mention at least the minimum inhibitory concentration or the inhibition degree of the extract(s) or isolated compound(s) considering the anti‐trypanosomal activity, (d) in cases where different authors present results for the same plants, the most recent results are prioritised unless they present more minor details such as cytotoxicity tests, (e) due to the volume of data available for African region medicinal plants, only plants whose bioactive compound have been isolated were reported herein. The EC50 below 25 µM or µg for pure compounds was considered the search limit for the whole region. The author aimed to review the tested medicinal plant extracts, not just the isolated compounds from plants. Literature was not used when the results came from an ethnobotanical survey without scientific investigation.

2.3. Data extraction

The information such as the species and family of the plant, the type of extraction, the active compound(s) if isolated, the strain of Trypanosoma tested, the 50% effective concentration and cytotoxic concentration, country of study and the name of the author were extracted from relevant literature and presented in the form of a table according to geographical location.

2.4. Ethical approval statement

An ethics statement is not applicable because this study is based exclusively on published literature.

3. RESULTS AND DISCUSSION

3.1. Analysis of the included literature

A total of 70 articles have been selected based on the inclusion criteria. Twenty studies reported African anti‐trypanosomal plants, 11 reported Asian anti‐trypanosomal plants, three reported the Middle East anti‐trypanosomal plants and 15 reported Latin American anti‐trypanosomal plants. Two studies reported North American anti‐trypanosomal plants, and nine studies reported European anti‐trypanosomal plants. One study reported Oceania's anti‐trypanosomal plants (Figure 1). A total of 70 relevant kinds of literature have been selected based on the inclusion criteria. The PRISMA 2020 flow diagram shows 25, 16, 18, 1, 9 and 1, including database searches (Figure 2) (Page et al., 2021).

FIGURE 1.

PRISMA 2020 flow diagram for which included searches of databases

FIGURE 2.

Chemical structures of isolated compounds from Africa medicinal plants

3.2. African region plants

Ethnobotanical resources for Africa demonstrated unusual plants with anti‐trypanosomal activity (Ibrahim et al., 2014; Lawal et al., 2015). We explained 264 and 215 plants, respectively, which were assessed for anti‐trypanosomal activity. Due to the high amount of data available for African region anti‐trypanosomal plants, only the plants with the minimum inhibitory concentration of the bioactive compound were scrutinised (Table 1 and Figure 3).

TABLE 1.

Plants assessed for anti‐trypanosomal activity and the EC50 of bioactive compounds isolated

Scientific name	Family	Part(s) used	Solvent	Bioactive compound(s)	Model	Sub species	cytotoxic/ biological activity	EC50	Country	References
Abrus precatorius L. subsp. africanus Verdc	Leguminosae	Leaf	Methanol	Abruquinone K, L, A and D	In vitro	T. b. r	57.3, 7.5, 34.5 and 4.8 µM	0.1, 0.02, 0.02 and 0.01 µM	South Africa	(Hata et al., 2014)
Aframomum letestuanum Gagnep	Zingiberaceae	Seed	DCM	Letestuianin C and 5‐hydroxy‐1,7‐bis(4‐hydroxyphenyl)hepta‐4,6‐dien‐3‐one	In vitro	T.b. b	‐	1.4 and 2.6 µg/ml	Cameroon	(Kamnaing et al., 2003)
Allexis cauliflora (Oliv.) Pierre	Violaceae	Leaf	DCM	22‐Hydroxyclerosterol	In vitro	T.b. b	1.12 µM	1.56 µM inhibit the glycolytic enzyme PGI	Cameroon	(Nganso et al., 2011)
Ancistrocladus abbreviatus subsp. lateralis Gereau	Ancistrocladaceae	Leaves, stem bark and roots	DCM	Ancistrocladidine, Ancistrotanzanines B and C, Ancistrotectoriline A and O,N‐dimethylancistrocladidine	In vitro	T.b.r T.c	28.3, 8.1, 40.7, 6.5 and 42.9 µg/ml	0.17 to 12.41 µM	Cameroon	(Simoben et al., 2018) (Bringmann et al. 2003, Bringmann et al. 2004)
Solanecio angulatus Crotalaria phillipsiae Artemisia annua L.	Fabaceae Asteraceae	Flower Twigs Leaf	DCM/ methanol	Artemisinin	In vitro	T.b. b	>500 27.39	12.17e, 12.47e µg/ml and 0.127 µM	Tanzania	(Nibret et al., 2009)
Azadirachta indica A.Juss.	Meliaceae	Leaf	Chloroform	7,15‐dihydroxy‐7,15‐deoxo nimbin	In vitro	T.b. r		15.6 µg/ml	Kenya	(Githua and Hassanali, 2011)
Buchholzia coriacea Engl	Capparaceae	Seeds	Methanol	Beta‐sitosterol α–sulphur	In vitro	T.b. b	No noticeable morphological changes	12.5 and 25 µg/ml	Nigeria	(Nweze, Anene and Asuzu, 2011)
Cassytha filiformis L.	Lauraceae	Leaf	DCM	Cassythine	In vitro	T.b. b	15.2 µM	6 µM	Cameroon	(Simoben et al., 2018)
Chrysanthemum cinerariifolium (Trevir.) Vis	Asteraceae	Flowers	n‐hexane	Cinerin (II) Pyrethrin (I,II) Jasmolin (II)	In vitro	T.b. r	28, 146.6, 95.1 and 31.5	12.2 6.9, 10.6 12 µg/ml	South Africa	(Hata et al., 2011)
Cussonia zimmermannii Harms	Araliaceae	Root bark	Petroleum ether extract	Polyacetylenes (MS‐1, MS‐2 and MS‐4)	In vitro	T.b.r/T.cr	54(17), 12(3.6) and 58(22) µM (µg/ml)	18 (5.4), 0.46 (0.14) and 1.1 (0.42)/ 26 (7.9), 0.65 (0.20) and 0.40 (0.15) µM (µg/ml)	Tanzania	(Senn et al., 2007)
Dioncophyllum thollonii Baill	Dioncophyllaceae	Roots	DCM	Dioncophylline E	In vitro	T.b.r/T.cr	‐	0.73 and 18.4 µg/ml	Cameroon	(Simoben et al., 2018)
Drypetes gerrardii Hutch.	Putranjivaceae	Stem	DCM/methanol	Putranoside A	In vitro	T.b. r	68.2 µM	18.0 µM	South Africa	(Hata et al., 2014)
Entada abyssinica A.Rich.	Leguminosae	Stem	Ethanol	Kolavenol	In vitro	T.b. r	‐	2.5 mg/ml (8.6 mM)	Tanzania	(Freiburghaus et al., 1998)
Eucalyptus maculata Hook.	Myrtaceae	Leaf	Hexane, ethyl acetate and methanol	Triterpenoid (3β,13β‐dihydroxy‐urs‐11‐en‐28‐oic acid)	In vitro	T. strains s427 WT, B48 and AQP2/3KO	1.58 µg/ml	1.58, 1.55 and 1.39 µg/ml	Nigeria	(Ebiloma et al., 2017)
Garcinia lucida Vesque	Clusiacea	Stem	DCM	Dihydrochelerythrine, 6‐acetonyldihydrochelerythrine, Lucidamine A	In vitro	T.b. b	35.4, 15.3 and 11.6 µM	0.8, 3.9 and 14.1 µM	Cameroon	(Fotie et al., 2007)
Keetia leucantha (K.Krause) Bridson	Rubiaceae	Leaf	DCM	Oleanolic acid/ursolic acid/betulinic acid/β‐ionone	In vitro	T. b.b	‐	7.3, 2.5, 19.1, 10.5 µg/ml	Nigeria	(Bero et al., 2013)
Khaya anthotheca (Welw.) C.DC.	Meliaceae	Seeds	Pet. ether	Grandifolione	In vitro	T.b.r/T.cr	44.7	10.66/20.9 µg/ml	Uganda	(Oboh, Lawal and Malann, 2013)
Mitracarpus scaber Zucc. ex Schult. & Schult.f.	Rubiaceae	Leaf	Methanol	Azaanthra‐quinone	In vitro/in vivo	T.co in bloodstream of BalbC mice, 50 mg/kg/d	‐/Inhibit reduced coenzyme Q1‐dependent O2	50 µg/ml	Nigeria	(Nok, 2002)
Morinda lucida Benth.	Rubiaceae	Leaves	Methanol	β‐sitosterol	In vitro	T.b. b	100	12.5 µg/ml	Nigeria	(Nweze, 2012)
Ocimum gratissimum L.	Lamilaceae	Seed oil	Oil	Myrcen, Limonen and Citronellal	In vitro	T.b. b	>50, >50 and >50 µg/ml	2.24, 4.24 and 2.76 µg/ml	Benin	(Kpadonou Kpoviessi et al., 2014)
Polyalthia longifolia (Sonn.) Thwaites	Annonaceae	Leaf	Hexane, ethyl acetate and methanol	Clerodane	In vitro	T.co	‐	0.38 µg/ml	Nigeria	(Ebiloma et al., 2017)
Polyalthia suaveolens Engl. & Diels	Annonaceae	Leaf	DCM	Mixture of polysin and greenwayodendrin‐3‐one	In vitro	T.b.b	170 µM	18 µM	Cameroon	(Simoben et al., 2018)
Schkuhria pinnata (Lam.) Kuntze ex Thell.	Asteraceae	Whole plant	DCM/methanol	Schkuhrin I and II	In vitro	T.b. r/T.cr	5.26 and 9.03 µM	0.9 and 1.5 µM/16.4 and 26.9 µM	South Africa	(Mokoka et al., 2013)
Strychnos spinosa Lam.	Loganiaceae	Leaf	Ipophilic	Saringosterol, 24‐hydroperoxy‐24‐vinylcholesterol	In vitro	T.b.b	>233.3 and 16.4 µM	7.8 and 3.2 µM	Tanzania	(Hoet et al., 2007)
Teclea trichocarpa (Engl.) Engl.	Rutaceae	Leaves	Methanol	Melicopicine, skimmianine and α‐amyrin	In vitro	T.b.r	>90, 38.6 and >90 µg/ml	15.56, 15.78, 11.21 µg/ml	Kenya	(Mwangi et al., 2010)
Terminalia actinophylla Mart.	Combretaceae	Leaf	Water	Terchebulin and punicalagin	In vitro	T.b. b	≥1500 and ≥1500 µg/ml	25 and 14 µM	Nigeria	(Shuaibu et al., 2008)
Toona ciliata M.Roem.	Meliaceae	Root	Methanol chloroform	Cedrelone	In vitro	T.b. r	‐	6.95Me, 3.2Ce and 7.85	Kenya	(Githua and Hassanali, 2011)
Vernonia guineensis Benth.	Asteraceae	Stem bark	Ethanol	Vernoguinosterol and vernoguinoside	In vitro	T.b. r	‐	3–5 µg/ml	Cameroon	(Tchinda et al., 2002)
Vernonia mespilifolia Less.	Asteraceae	Leaf	DCM/methanol	Cynaropicrin	In vitro	T.b. r/T.cr	1.29 µM	0.23 µM/5.14 µM	South Africa	(Mokoka et al., 2013)
Waltheria indica L.	Malvaceae	Root	DCM	Waltheriones L	In vitro	T.cr/ T.b.b/T.b.r	‐	0.74e, 20e, 17.4e µg/ml and 3.1 µM	Cameroon	(Simoben et al., 2018)
Warburgia ugandensis subsp. ugandensis	Canellaceae	Leaf	DCM	Muzigadiolide muzigadial, 6α,9α‐dihydroxy‐4(13),7‐coloratadiene‐11,12‐dial and mukaadial and ugandensidial	In vitro	T.b.r	‐	0.64 to 6.4 µM	Cameroon	(Simoben et al., 2018)
Zapoteca portoricensis (Jacq.) H.M.Hern.	Fabaceae	Leaf	DCM	Saropeptide or aurantiamide acetate	In vitro	T.b.r/T.c	92.05 µM	3.63 and 41.65 µM	Cameroon	(Simoben et al., 2018)

Abbreviations: EC50, half maximal inhibitory concentration (µg/ml); T.b. b, Trypanosoma brucei brucei; T.e, Trypanosoma evansi; T. co, Trypanosoma congolense

^eExtract.

^MeMethanolic extract.

^CeChloroform extract.

FIGURE 3.

Chemical structures of isolated compounds from Asia medicinal plants

More than 200 investigated plants (Ibrahim et al., 2014; Lawal et al., 2015) show potential trypanocidal activity; only 34 plants have their active compounds isolated in pure form. Only their compounds (flavonoid, saponins, alkaloid etc.) are reported for the other plants. This is due to the lack of resources in Africa to isolate the active molecules. Among these 34 plants, just six have been investigated in vivo. The anti‐trypanosomal activity of the extracts was most assessed on Trypanosoma brucei subspecies, which are responsible for African trypanosomiases (WHO, 2015). Considering the importance of trypanosomiases caused by this species in Africa, the development of anti‐trypanosomal medicine based on plants has been an exciting research topic.

Additionally, the medicinal plants of Africa provide a large variety of bioactive compounds. Of the 24 plants reported in Table 1, approximately 34 different bioactive compounds were isolated with trypanosomiases activity. Some plants, such as Chrysanthemum cinerariifolium, Keetia leucantha, Tecla trichocarpa and Terminalia avicenioides, provide at least three different potent bioactive compounds.

Concerning the criteria for choosing compounds with anti‐trypanosomal potential, EC50>20 µg/ml is considered ineffective (Pink et al., 2005). Thus, approximately 40 compounds seem to be effective (EC50<20 µg/ml) and have demonstrated promising anti‐trypanocidal activity (Figure 2). Given the minimum inhibitory concentration, only abruquinone (0.01 µg/ml) has a concentration closer to Melarsoprol reference (0.004 µg/ml) was active against Trypanosoma brucei and benznidazole (0.482 µg/ml) reference was active against Trypanosoma cruzi.

3.3. Asia plants

Asia plants assessed for anti‐trypanosomal activity with EC50 values for inhibition of parasites and cytotoxicity are shown in Table 2.

TABLE 2.

Plants assessed for anti‐trypanosomal activity in in vitro model

Scientific name	Family	Part (s) used	Solvent	Bioactive compound	Sub species	EC50	CC50 *	Country	References
Alnus japonica (Thunb.) Steud.	Betulaceae	Bark	DCM	Oregonin Hirsutanone	T.b	1.14 and 1.78 µM	50 µM	Japan	(Tung et al., 2014)
Aquilaria malaccensis Lam.	Thymelaeaceae	Leaves	Ethanol	‐	T.e	128.63 µg/ml	259.78 µg/ml	Malaysia	(Dyary et al., 2014)
Andrographis paniculata (Burm.f.) Nees	Acanthaceae	Leaves/stems	Methanol	‐	T.e	54.7 µg/ml	55.1 µg/ml	Japan	(Bawm, 2010)
Brucea javanica (L.) Merr.	Simaroubaceae	Fruit	Methanol	‐	T.e T.b	27.2 µg/ml	309.15 µg/ml	Japan	(Bawm, 2010)
Combretum acuminatum Roxb.	Combretaceae	Rhizomes	Methanol	‐	T.e	90.7 µg/ml	853.15 µg/ml	Japan	(Bawm, 2010)
Cordyline terminalis (L.) Kunth	Liliaceae	Leaves	Water	‐	T.e	48.1 µg/ml		Malaysia	(Dyary et al., 2019)
Crateva religiosa G.Forst	Capparidaceae	Leaves/stems	Methanol	‐	T.e	107.1 µg/ml	691 µg/ml	Japan	(Bawm, 2010)
Curcuma longa L.	Zingiberaceae	Leaves	Oil	Curlone	T.b.b	1.38 µg/ml		Vietnam	(Le et al., 2019)
Curcuma zedoaria (Christm.) Roscoe	Zingiberaceae	Leaves	Oil	‐	T.b.b	2.51 µg/ml		Vietnam	(Le et al., 2019)
Derris elliptica (Wall.) Benth.	Fabaceae	Leaves	Ethanolic	‐	T.e	17.79 µg/ml	331.90 µg/ml	Malaysia	(Dyary et al., 2014)
Eucalyptus globulus Labill.	Myrtaceae	Leaf	Methanol	‐	T.e	51.1 µg/ml	622.95 µg/ml	Japan	(Bawm, 2010)
Garcinia hombroniana Pierre	Clusiaceae	Leaves	Ethanolic	‐	T.e	103.44 µg/ml	10.17 µg/ml	Malaysia	(Dyary et al., 2014)
Goniothalamus tapis Miq.	Annonaceae	Leaves	Ethanolic	‐	T.e	7.61 µg/ml	‐	Malaysia	(Dyary et al., 2019)
Goniothalamus umbrosus J.Sinclair	Annonaceae	Leaves	Ethanolic	‐	T.e	2.30 µg/ml	29.10 µg/ml	Malaysia	(Dyary et al., 2014)
Iris domestica (L.) Goldblatt & Mabb.	Iridaceae	Leaves	Petroleum ether	Isoiridogermanal	T.b.b	3.60 µg/ml	136.00 µg/ml	China	(Pathiranage et al., 2016)
Jatropha podagrica Hook.	Euphorbiaceae	Fruit	Methanol	‐	T.e	52.3 µg/ml	652.7 µg/ml	Japan	(Bawm, 2010)
Litsea cubeba (Lour.) Pers.	Lauraceae	Leaves	Oil	‐	T.b.b	1.12 nL/ml		Vietnam	(Le et al., 2019)
Murraya koenigii (L.) Spreng.	Rutaceae	Leaves		Mahanimbine, murrayafoline and girinimbine	T.e	3.13, 6.35 and 10.16 µg/ml	745.58 µg/ml	Malaysia	(Dyary et al., 2019)
Nigella sativa L.	Ranunculaceae	Seeds	Ethanolic	‐	T.e	291.72 µg/ml	381.59 µg/ml	Malaysia	(Dyary et al., 2014)
Orthosiphon stamineus Benth.	Labiatae	Leaves	Methanol	‐	T.e	144.7 µg/ml	628.9 µg/ml	Japan	(Bawm, 2010)
Phyllanthus simplex Retz.	Euphorbiaceae	Leaves/stem	Methanol	‐	T.e	96.1 µg/ml	98.8 µg/ml	Japan	(Bawm, 2010)
Plumbago rosea L.	Plumbaginaceae	Flowers	Methanol	‐	T.e	156.7 µg/ml	557.05 µg/ml	Japan	(Bawm, 2010)
Polygonum hydropiper L.	Polygonaceae	Leaves	DCM	Vanicoside E, (+)‐ketopinoresinol, isorhamnetin and cardamomin	T.b	0.49–7.77 µg/ml	‐	China	(Xiao et al., 2017)
Punica granatum L.	Lythraceae	Leaves	Ethanol	‐	T.e	20 mg/ml	‐	India	(Kumar et al., 2014)
Quercus borealis F.Michx.	‎Fagaceae	Roots	Methanol	‐	T.e	250 µg/ml		India	(Shaba et al., 2011)
Rhoeo discolor (L'Hér.) Hance	Commelinaceae	Leaves	Methanol	‐	T.e	75.8 µg/ml	424.9 µg/ml	Japan	(Bawm, 2010)
Scutellaria baicalensis Georgi	Lamiaceae	Leaves	Water/chloroform	‐	T.b	11.43 µg/ml 19.56 µg/ml	‐	China	(Floyd, 2013)
Strobilanthes abbreviata Y.F. Deng & J.R.I. Wood	Acanthaceae	Leaves	Ethanolic	‐	T.e	52.54 µg/ml	355.21 µg/ml	Malaysia	(Dyary et al., 2014)
Vitex arborea Desf.	Verbenaceae	Leaves/stem	Methanol	‐	T.e	48.6 µg/ml	735.15 µg/ml	Japan	(Bawm, 2010)
Vitis repens (Lam.) Wight & Arn.	Vitaceae	Root bark	Methanol	‐	T.e	8.6 µg/ml	209.9 µg/ml	Japan	(Bawm, 2010)
Zingiber officinale Roscoe	Zingiberaceae	Leaves	Oil	‐	T.b.b	3.10 nL/ml		Vietnam	(Le et al., 2019)

Note: The EC50 values for inhibition of parasites and the cytotoxicity are shown

^*The extract concentration that reduced the cell viability by 50% when compared to untreated controls.

A total of 31 plants with their minimum inhibitory concentration have been identified in the literature. Four plants (V. repens, P. simplex, V. arborea and A. brevipedunculata) already have bioactive compounds. These seven compounds include resveratrol (EC50 = 31.4), 11‐O‐acetyl‐bergenin (EC50 = 61.2), stigmas‐4‐ en‐3‐ one (EC50 = 62.8), lupeol (EC50 = 98.4), Ψ‐taraxasterone (EC50 = 115.4), hopenyl‐3β‐O‐palmitate (EC50 = 68.2) and β‐amyrin palmitate (EC50 = 60.8) (Bawm, 2010). The extracts were mostly evaluated on Trypanosoma evansi due to its prevalence in Asia (Dyary et al., 2014). Considering the potency criteria asserted by Pink et al. (2005), it was expressed that the isolated compounds with an EC50> 20 µg/ml were not considered effective drugs. Thus, the seven isolated compounds may not be considered lead drugs. There is a need to pursue investigations that isolate more effective compounds. On the other hand, as suggested by Pink et al. (2005), crude extracts with potent in vivo anti‐trypanosomal activity such as <100 mg/kg with no toxic effect below 800 mg/kg may be considered promising lead structures. None of the plants with in vitro data were evaluated in vivo. The minimum inhibitory concentration of the methanolic extract of Goniothalamus umbrosus (2.30 µg/ml) was the only extract with an activity profile closer to the diminazene aceturate (0.01140 µg/ml) reference against Trypanosoma evansi.

3.4. Middle East

Table 3 shows a list of plants in the Middle East with cytotoxicity values against trypanosome parasite activity. Al‐Musayeib et al. (2012) reported 41 medicinal plants used in Saudi Arabia that showed anti‐trypanosomal activity in vitro. All of their inhibitory activities are explained by the EC50 and CC50. However, no details have been given about their bioactive compounds except their secondary metabolite composition. Their activity profile in in vivo studies is unknown, so their therapeutic potential remains to be established.

TABLE 3.

Plants assessed for in vitro model of anti‐trypanosomal activity in Saudi Arabia which the EC50 and the cytotoxicity values are known

ScientificName	Family	Part (s) used	Solvent	Sub species	EC50	CC50	References
Ajuga bracteosa Wall. ex Benth.	Labiatae	Leaves	Methanol	T.c T.b.b	28.8 μg/ml	31.2 μg/ml	(Al‐Musayeib, Mothana, Matheeussen, et al., 2012)
Albizia lebbeck (L.) Benth.	Leguminosae	Stems	Methanol	T.c T.b.b	8.7 μg/ml 8.1 μg/ml	32.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Cadaba farinosa subsp. adenotricha (Gilg & Benedict) R.A.Graham	Capparaceae	Leaves/stems	Methanol	T.c T.b.b	28.6 μg/ml 10.6 μg/ml	32.9 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Cadaba glandulosa Forssk.	Capparaceae	Leaves/Stems	Methanol	T.c T.b.b	36.5 μg/ml 16.4 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Caralluma quadrangula (Forssk.) N.E.Br.	Asclepiad‐aceae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml 32.5 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Caralluma sinaica (Decne.) A.Berger	Asclepiad‐aceae	Leaves	Methanol	T.c T.b.b	7.3 μg/ml 7.7 μg/ml	20.5 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Celtis africana Burm.f.	Cannabaceae	Leaves/stems	Methanol	T.c T.b.b	29.4 μg/ml >64.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Centaurea pseudosinaica Czerep.	Asteraceae	Leaves	Methanol	T.c T.b.b	31.0 μg/ml 9.1 μg/ml	16.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Chrozophora oblongifolia (Delile) A.Juss. ex Spreng.	Euphorbiacea	Leaves	Methanol	T.c T.b.b	32.0 μg/ml 10.8 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Conocarpus lancifolius Engl.	Combretaceae	Fruits	Methanol	T.c T.b.b	32.2 μg/ml 35.2 μg/ml	7.2 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Cordia sinensis Lam.	Boragin‐aceae	Leaves/stems	Methanol	T.c T.b.b	33.9 μg/ml 32.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Costus arabicus L.	Zingiberaceae	Roots	Methanol	T.c T.b.b	13.8 μg/ml 30.0 μg/ml	38.5 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Cupressus sempervirens L.	Cupressaceae	Leaves	Methanol	T.c T.b.b	8.3 μg/ml 2.1 μg/ml	10.7 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Dorstenia barnimiana Schweinf.	Moraceae	Leaves	Methanol	T.c T.b.b	29.6 μg/ml 22.6 μg/ml	49.4 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Dodonaea viscosa (L.) Jacq.	Sapindaceae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml 11.1 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Enicostemma verticillare L.	Gentianaceae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml	9.9 ± 1.1 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Ficus cordata subsp. salicifolia (Vahl) C.C.Berg	Moraceae	Leaves	Methanol	T.c T.b.b	26.3 μg/ml	8.2 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Ficus ingens (Miq.) Miq.	Moraceae	Leaves	Methanol	T.c T.b.b	31.2 μg/ml 8.0 μg/ml	32.5 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Ficus palmata subsp. virgata Browicz	Moraceae	Leaves	Methanol	T.c T.b.b	22.6 μg/ml 8.1 μg/ml	37.7 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Grewia erythraea Schweinf.	Tiliaceae	Leaves	Methanol	T.c T.b.b	8.2 μg/ml 2.6 μg/ml	27.2 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Iris albicans var. madonna Dykes	Iridaceae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml 10.6 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Iris germanica L.	Iridaceae	Roots	Methanol	T.c T.b.b	24.6 μg/ml 8.2 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Kanahia laniflora (Forssk.) R.Br.	Iridaceae	Leaves	Methanol	T.c T.b.b	0.4 μg/ml 9.6 μg/ml	0.8 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Kniphofia sumarae Deflers	Asclepiadaceae	Leaves	Methanol	T.c T.b.b	31.4 μg/ml 5.9 μg/ml	7.4 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Lavandula dentata var. candicans Batt.	Liliaceae	Leaves	Methanol	T.c T.b.b	7.9 μg/ml 3.0 μg/ml	29.6 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Leucas inflata Benth.	Labiatae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml 8.4 μg/ml	29.5 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Nigella sativa var. hispidula Boiss.	Ranuncul‐aceae	Seeds	Methanol	T.c T.b.b	>64.0 μg/ml >64.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Periploca aphylla Decne.	Asclepiad‐aceae	Leaves/stems	Methanol	T.c T.b.b	8.1 μg/ml 7.1 μg/ml	23.9 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Phoenix dactylifera L.	Arecaceae	Seeds	Methanol	T.c T.b.b	46.5 μg/ml 36.2 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Plectranthus barbatus var. grandis (L.H.Cramer) Lukhoba & A.J.Paton	Labiatae	Leaves	Methanol	T.c T.b.b	23.3 μg/ml 2.6 μg/ml	32.9 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Prosopis juliflora var. horrida (Kunth) Burkart	Leguminosae	Fruits	Methanol	T.c T.b.b	10.4 μg/ml 2.0 μg/ml	49.8 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Pulicaria inuloides (Poir.) DC.	Labiatae	Leaves	Methanol	T.c T.b.b	31.7 μg/ml 7.8 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Punica granatum L.	Punicaceae	Fruits	Methanol	T.c T.b.b	35.2 μg/ml 34.3 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Rhus retinorrhaea Steud. ex A.Rich.	Anacardiaceae	Leaves	Methanol	T.c T.b.b	30.5 μg/ml 34.0 μg/ml	53.2 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Ribes nigrum L.	Grossulari‐aceae	Fruits	Methanol	T.c T.b.b	>64.0 μg/ml >64.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Salvadora persica var. persica	Sallvador‐aceae	Leaves/stems	Methanol	T.c T.b.b	30.1 μg/ml 32.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Tagetes minuta L.	Asteraceae	Leaves	Methanol	T.c T.b.b	9.2 μg/ml 2.2 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Tarconanthus camphoratus L.	Asteraceae	Leaves	Methanol	T.c T.b.b	>64.0 μg/ml >64.0 μg/ml	>64.0 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Teucrium yemense Deflers	Labiatae	Leaves	Methanol	T.c T.b.b	30.5 μg/ml 7.1 μg/ml	27.2 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Vernonia leopoldi (Sch.Bip. ex Walp.) Vatke	Asteraceae	Leaves	Methanol	T.c T.b.b	9.2 μg/ml 8.0 μg/ml	30.1 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)
Zingiber officinale var. cholmondeleyi F.M.Bailey	Zingiber‐aceae	Roots	Methanol	T.c T.b.b	>64.0 μg/ml 39.4 μg/ml	34.3 μg/ml	(Al‐Musayeib, Mothana, Al‐Massarani, et al., 2012)

3.5. European plants

A total of 27 plants studied in Europe have been extracted from the literature. Of these, only three plants have bioactive compounds. The milestone was the most efficient bioactive compound with a minimum inhibitory concentration of 0.5 µg/ml (Ślusarczyk et al., 2011). Trypanosoma brucei was the most studied parasite, and a large variety of ethnobotanical families were included (Table 4 and Figure 4).

TABLE 4.

Plants assessed for anti‐trypanosomal activity which the EC50 and the cytotoxicity values are known

Scientific name	Family	Part(s) used	Solvent	Bioactive compound	Model	Sub species	EC50	CC50	Country	References
Arctium nemorosum Lej.	Asteraceae	Leaf	Methanol	Onopordopicrin	In vitro	T.b.r	0.37 μM	3.06 μM	Switzerland	(Zimmermann et al., 2012)
Arnica montana L.	‎Asteraceae	Leaf	DCM	‐	In vitro	T.b.r	1.12 μg/ml	12.1 μg/ml	Germany	(Llurba‐Montesino et al., 2015)
Callitris neocaledonica Dümmer	Cupressaceae	Wood	Water	‐	In vitro	T.b.b	>50 μg/ml	>50 μg/ml	France	(Desrivot et al., 2007)
Callitris sulcata (Parl.) Schltr.	Cupressaceae	Wood	Water	‐	In vitro	T.b.b	>50 μg/ml	>50 μg/ml	France	(Desrivot et al., 2007)
Citrus macroptera Montrouz.	Rutaceae	Leaves	Water	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Crinum stuhlmannii subsp. delagoense (I.Verd.) Kwembeya & Nordal	Amaryllidaceae	Leaves	Ethanol	‐	In vitro	T.c	0.70 μM	21.87 μM	Spain	(Martinez‐Peinado et al., 2020)
Curcuma longa L.	Zingiberaceae	Leaves	Water	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Dodonea viscosa L.	Sapindaceae	Leaves	Ethanol	‐	In vitro	T.b.b	61.4 μg/ml	‐	France	(Desrivot et al., 2007)
Eugenia uniflora L	Myrtaceae	Bark	Water	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Eugenia uniflora L.	Moraceae	Leaves	Methanol	‐	In vitro	T.b.b	46 μg/ml	‐	France	(Desrivot et al., 2007)
Hernandia cordigera Vieill.	Hernandiaceae	Bark	DCM	‐	In vitro	T.b.b	48 μg/ml	‐	France	(Desrivot et al., 2007)
Homalium deplanchei Warb.	Flacourtiaceae	Bark	DCM	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Hyacinthoides non‐scripta (L.) Chouard ex Rothm.	Asparagaceae	Flowers	Methanol	‐	In vitro	T.b.b	11.1 μg/ml	‐	UK	(Raheem et al., 2019)
Juncus acutus subsp. acutus	Juncaceae	Leaves	DCM	Juncunol	In vitro	T.c	4.1 μg/ml	6.0 μg/ml	Portugal	(Oliveira et al., 2016)
Manilkara dissecta (L.f.) Dubard	Sapotaceae	Leaves	DCM	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Murraya crenulata (Turcz.) Oliv.	Rutaceae	Bark	Hexane	‐	In vitro	T.b.b	27.6 μg/ml	‐	France	(Desrivot et al., 2007)
Myoporum crassifolium G.Forst.	Myoporaceae	Wood	Water	‐	In vitro	T.b.b	16 μg/ml	‐	France	(Desrivot et al., 2007)
Myoporum tenuifolium G.Forst.	Myoporaceae	Leaves	DCM	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Myristica fatua Houtt.	Myristicacae	Almonds	DCM	‐	In vitro	T.b.b	0.5 μg/ml	‐	France	(Desrivot et al., 2007)
Narcissus broussonetii var. grandiflorus Batt. & Trab.	Amaryllidaceae	Leaves	Ethanol	‐	In vitro	T.c	0.495 μM	5.21 μM	Espain	(Martinez‐Peinado et al., 2020)
Premna serratifolia L.	Lamiaceae	Bark	DCM	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Prumnopytis ferruginoides L.	Podocarpaceae	Leaves	Water	‐	In vitro	T.b.b	>50 μg/ml	‐	France	(Desrivot et al., 2007)
Salvia officinalis subsp. gallica (W.Lippert) Reales, D.Rivera & Obón	‎Lamiaceae	Leaves	DCM	‐	In vitro	T.b.r	1.86 μg/ml	32.3 μg/ml	Germany	(Llurba‐Montesino et al., 2015)
Salvia miltiorrhiza var. charbonnelii (H.Lév.) C.Y.Wu	Lamiaceae	Roots	DCM	Miltirone	In vitro	T.b.r	0.5 μg/ml	1.3 μg/ml	Switzerland	(Ślusarczyk et al., 2011)
Scaevola balansae Guillaumin	Goodneniaceae	Bark	DCM	‐	In vitro	T.b.b	39 μg/ml	‐	France	(Desrivot et al., 2007)
Valeriana officinalis subsp. collina (Wallr.) Nyman	Caprifoliaceae	Leaves	Ethanol	‐	In vitro	T.c	5.87 μg/ml	5.28 μg/ml	Germany	(Llurba‐Montesino et al., 2015)
Wollastonia biflora (L.) DC.	Asteraceae	Leaves	DCM	‐	In vitro	T.b.b	>100 μg/ml	‐	France	(Desrivot et al., 2007)

FIGURE 4.

Chemical structures of isolated compounds from Europe medicinal plants

3.6. Latin America

A total of 165 plants have been reported throughout the literature, and just four have their isolated known compound. Researchers from South America have contributed to the investigation of anti‐trypanosomal plants. This result corroborates the scientometric analysis of global trypanosomiases research from 1988 to 2017, showing that South America ranked second behind Europe for contributions to trypanosomiases research (Hassan et al., 2020). The crude extracts of Anthemis tinctoria (semi‐purified), Caseria sylvestris (hexane) and Ranunculus sceleratus (ethanol) showed inhibitory activity against Trypanosoma cruzi with a minimum inhibitory concentration of 0.2, 0.3 and 0.7 µg/ml, respectively. For many plants, parasite growth inhibition is generally reported; thus, the minimum inhibitory concentration remains unknown (Table 5 and Figure 5).

TABLE 5.

Plants assessed for anti‐trypanosomal activity which the EC50 values are known

Scientific name	Family	Part(s) used	Solvent	Bioactive compound	Model	Sub species	EC50	CC50	Country	References
Abuta pahni (Mart.) Krukoff & Barneby	Menisper maceae	Stems	petroleum ether, chloroform, ethyl acetate or 50% ethanol	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Acnistus arborescens (L.) Schltdl.	Solanaceae	Leaf	Ethanol	‐	In vitro	T.c	4 μg/ml	‐	Panama	(Calderón et al., 2010)
Aechmea distichantha var. glaziovii (Baker) L.B.Sm.	Bromeliaceae	Leaf	Methanol	‐	In vitro	T.c	48 μg/ml	‐	Panama	(Calderón et al., 2010)
Aiouea trinervis Meisn.	Lauraceae	Leaf	Ethanol	Isoobtusi‐Lactone A	In vitro	T.c	2.75 μg/ml	156.45 μg/ml	Brazil	(Nunes et al., 2020)
Angelica dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav.	Apiaceae	Root	Ethanol	‐	In vitro	T.c	14.5 μg/ml	‐	Argentina	(Schinella et al., 2002)
Angelica pubescens f. biserrata R.H.Shan & C.Q.Yuan	Apiaceae	Root	Ethanol	‐	In vitro	T.c	14.9 μg/ml	‐	Argentina	(Schinella et al., 2002)
Angelica sinensis (Oliv.) Diels	Apiaceae	Wood	Ethanol	‐	In vitro	T.c	19.4 μg/ml	‐	Argentina	(Schinella et al., 2002)
Annona crassiflora Mart.	Annonaceae	Root bark	Ethanol	‐	In vitro	T.c	5.9 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Annona muricata L.	Annonaceae	Leaf	Ethanol		In vitro	T.c	10 μg/ml	‐	Panama	(Calderón et al., 2010)
Anomospermum chloranthum subsp. occidentale (Cuatrec.) Krukoff & Barneby	Menisper maceae	Leaf	Alkaloid	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Anthemis tinctoria subsp. australis R.Fern.	‎Asteraceae	Flowers	Semi‐purified	‐	In vitro	T.c	0.2 μg/ml	7.0 μg/ml	Brazil	(Bittencourt et al., 2011)
Astragalus pehuenches Niederl.	Fabaceae	Bark	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Ardisia densiflora Krug & Urb.	Myrsinaceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Argemone subfusiformis Ownbey	Papaveraceae	Fruit	Methanol	‐	In vitro	T.c	10 μg/ml	‐	Panama	(Calderón et al., 2010)
Aristoloquia pilosa L.	Aristolochiaceae	Stem	Hexane	‐	In vitro	T.c	100%	‐	Peru	(González‐Coloma et al., 2012)
Artemisia mexicana Willd.	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	39.25 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Atractyloides macrocephala L.	Asteraceae	Root	Ethanol	‐	In vitro	T.c	23.0 μg/ml	‐	Argentina	(Schinella et al., 2002)
Astragalus membranaceus (Fisch.) Bunge	Fabaceae	Root	Water	‐	In vitro	T.c	13.5 μg/ml	‐	Argentina	(Schinella et al., 2002)
Astronium fraxinifolium Schott	Anacardiaceae	Stems bark	Hexane	‐	In vitro	T.b.r	16.4 μg/ml	>100 μg/ml	Brazil	(Charneau et al., 2016)
Baccharis notosergila Griseb.	Asteracea	Aerial parts	Methanol	‐	In vitro	T.c	>50 μg/ml	‐	Panama	(Calderón et al., 2010)
Baccharis trinervis var. cinerea (DC.) Baker	Asteraceae	Aerial parts	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Berberis conferta var. boliviana (Lechl.) C.K.Schneid.	Berberidaceae	Stems	Alkaloid	‐	In vitro	T.c	75 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Berberis microphylla G.Forst.	Berberidaceae	Aerial parts	Methanol	‐	In vitro	T.c	38.4 μg/ml	‐	Chile	(Muñoz et al., 2013)
Blepharocalyx salicifolius (Kunth) O.Berg	Myrtaceae	Leaves	Ethanol	‐	In vitro	T.c	37.3 μg/ml	55.1 μg/ml	Brazil	(Charneau et al., 2016)
Bocconia integrifolia var. mexicana DC.	Papaveraceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Bourreria huanita (Lex.) Hemsl.	Boraginaceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Bourreria spathulata (Miers) Hemsl.	Boraginaceae	Leaf	Methanol	‐	In vitro	T.c	30 μg/ml	‐	Panama	(Calderón et al., 2010)
Brunfelsia grandiflora D.Don	Solanaceae	Stem	Hexane	‐	In vitro	T.c	98%	‐	Peru	(González‐Coloma et al., 2012)
Caesalpinia paraguariensis (Parodi) Burkart	Fabaceae	Leaf	Ethanol	‐	In vitro	T.c	10 μg/ml	‐	Panama	(Calderón et al., 2010)
Calea jamaicensis var. jamaicensis	Asteraceae	Aerial parts	Ethanol	‐	In vitro	T.c	30 μg/ml	‐	Panama	(Calderón et al., 2010)
Calea peruviana (Kunth) Benth. ex S.F.Blake	Asteraceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Capraria biflora f. hirta Loes.	Scrophulariaceae	Aerial parts	Ethanol	‐	In vitro	T.c	46 μg/ml	‐	Panama	(Calderón et al., 2010)
Capparis salicifolia Griseb.	Capparaceae	Leaf	Ethanol	‐	In vitro	T.c	39 μg/ml	‐	Panama	(Calderón et al., 2010)
Cardiopetalum calophyllum Schltdl.	Annonaceae	Stem bark	Hexane	‐	In vitro	T.c	60.4 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Cardiopetalum calophyllum Schltdl.	Annonaceae	Leaves	Alkaloidal	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Casearia sylvestris var. lingua (Cambess.) Eichler	Flacourtiaceae	Root bark	Hexane	‐	In vitro	T.c	0.3 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Cedrela odorata var. xerogeiton Rizzini & Heringer	Meliaceae	Bark	Hexane	‐	In vitro	T.c	100%	‐	Peru	(González‐Coloma et al., 2012)
Cestrum parqui (Lam.) L'Hér.	Solanaceae	Aerial parts	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Chamaecrista desvauxii (Collad.) Killip	Caesalpiniaceae	Leaves	Ethanol	‐	In vitro	T.c	>80%	‐	Brazil	(Charneau et al., 2016)
Chondodendron tomentosum L.	Menispermaceae	Bark	Chloroform	‐	In vitro	T.c	100%	‐	Peru	(González‐Coloma et al., 2012)
Chromolaena leivensis (Hieron.) R.M.King & H.Rob.	Asteraceae	Aerial parts	Ethanol	‐	In vitro	T.c	8 μg/ml	‐	Panama	(Calderón et al., 2010)
Cinchona pubescens var. heterophylla Pav. ex DC.	Rubiaceae	Leaf	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Cissampelos tropaeolifolia var. fluminensis (Eichler) Diels	Menispermaceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Clarisia biflora Ruiz & Pav.	Moraceae	Aerial parts	Ethanol	‐	In vitro	T.c	25 μg/ml	‐	Panama	(Calderón et al., 2010)
Clematis campestris var. mendocina (Phil.) Hauman & Irigoyen	Ranunculaceae	Flowers	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Combretum laxum var. epiphyticum (Pittier) Croat	Combretaceae	Aerial parts	Methanol	‐	In vitro	T.c	34 μg/ml	‐	Panama	(Calderón et al., 2010)
Codonopsis pilosula var. glaberrima (Nannf.) P.C.Tsoong	Campanulaceae	Roots	Water	‐	In vitro	T.c	20.8 μg/ml	‐	Argentina	(Schinella et al., 2002)
Connarus suberosus var. fulvus (Planch.) Forero	Connaraceae	Roots woods	Hexane	‐	In vitro	T.b.r	1.7 μg/ml	2.6 μg/ml	Brazil	(Charneau et al., 2016)
Cordia cylindrostachya (Ruiz & Pav.) Roem. & Schult.	Boraginaceae	Leaf	Ethanol	‐	In vitro	T.c	35 μg/ml	‐	Panama	(Calderón et al., 2010)
Crataegus pubescens (C.Presl) C.Presl	Rosaceae	Fruit	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Critonia morifolia (Mill.) R.M.King & H.Rob.	Asteraceae	Fruit	Ethanol	‐	In vitro	T.c	29 μg/ml	‐	Panama	(Calderón et al., 2010)
Curcuma aromatic L.	Zingiberaceae	Rhizome	Water	‐	In vitro	T.c	21.4 μg/ml	‐	Argentina	(Schinella et al., 2002)
Cymbopogon citratus (DC.) Stapf	Poaceae	Aerial parts	Methanol	‐	In vitro	T.c	68.25 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Dalbergia ecastaphyllum (L.) Taub.	Fabaceae	Plant resin	Hydroethanol	‐	In vitro	T.c	88.86 μg/ml	228.02 μg/ml	Brazil	(Regueira‐Neto et al., 2018)
Drimys winteri J.R.Forst. & G.Forst.	Winteraceae	Aerial parts	DCM	Drimenol	In vitro	T.c	25.1 μg/ml	‐	Chile	(Muñoz et al., 2013)
Duguetia furfuracea (A.St.‐Hil.) Saff.	Annonaceae	Root bark	Hexane	‐	In vitro	T.c	6.6 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Egletes viscosa var. dissecta Shinners	Asteraceae	Whole plants	Ethanol	‐	In vitro	T.c	38 μg/ml	‐	Panama	(Calderón et al., 2010)
Eirmocephala brachiata H.Rob.	Asteraceae	Leaf	Ethanol	‐	In vitro	T.c	33 μg/ml	‐	Panama	(Calderón et al., 2010)
Eryngium heterophyllum Engelm.	Apiaceae	Aerial parts	Methanol	‐	In vitro	T.c	11.24 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Euterpe precatoria var. longivaginata (Mart.) A.J.Hend.	Arecaceae	Root	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Forsythia suspensa (Thunb.) Vahl	Oleaceae	Fruit	Methanol	‐	In vitro	T.c	19.1 μg/ml	‐	Argentina	(Schinella et al., 2002)
Fuchsia boliviana var. luxurians I.M.Johnst.	Onagraceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Galium latoramosum Clos	Rubiaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Gnaphalium gaudichaudianum var. gaudichaudianum	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	36 μg/ml	‐	Panama	(Calderón et al., 2010)
Gochnatia glutinosa (D.Don) D.Don ex Hook. & Arn.	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	20 μg/ml	‐	Panama	(Calderón et al., 2010)
Haematoxylum brasiletto H.Karst.	Fabaceae	Bark	Methanol	‐	In vitro	T.c	7.92 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Haplophyllum hispanicum Spach	Rutaceae	Fruit	Ethanol	‐	In vitro	T.c	8.5 μg/ml	16.7	Argentina	(Schinella et al., 2002)
Hauya lucida Donn.Sm. & Rose	Onagraceae	Aerial parts	Methanol	‐	In vitro	T.c	32 μg/ml	‐	Panama	(Calderón et al., 2010)
Helichrysum italicum (Roth) G.Don	Rutaceae	Aerial parts	Methanol	‐	In vitro	T.c	23.0 μg/ml	‐	Argentina	(Schinella et al., 2002)
Himatanthus obovatus (Müll.Arg.) Woodson	Apocynaceae	Root wood	Ethanol	‐	In vitro	T.c	15.7 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Ilex guayusa Loes.	Aquifoliaceae	Leaf	Ethanol	‐	In vitro	T.c	47 μg/ml	‐	Panama	(Calderón et al., 2010)
Inula viscosa (L.) Aiton	Asteraceae	Aerial parts	Ethanol	‐	In vitro	T.c	27.5 μg/ml	‐	Argentina	(Schinella et al., 2002)
Ipomoea carnea subsp. carnea	Convolvulaceae	Leaf	Ethanol	‐	In vitro	T.c	48 μg/ml	‐	Panama	(Calderón et al., 2010)
Jacaranda mimosifolia D.Don	Bignoniaceae	Leaf	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Kageneckia oblonga Ruiz & Pav.	Rosaceae	Aerial parts	Methanol	‐	In vitro	T.c	35.7 μg/ml	‐	Chile	(Muñoz et al., 2013)
Larrea cuneifolia Cav.	Zygophyllaceae	Aerial parts	Methanol	‐	In vitro	T.c	40 μg/ml	‐	Panama	(Calderón et al., 2010)
Lippia graveolens Kunth	Verbenaceae	Leaf	Ethanol	‐	In vitro	T.c	13 μg/ml	‐	Panama	(Calderón et al., 2010)
Lithrea caustica Hook. & Arn.	Anacardiaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Lentinus edodes L.	Marasmiaceae	Sclerotium	Water	‐	In vitro	T.c	26.8 μg/ml	‐	Argentina	(Schinella et al., 2002)
Lozania pittieri (S.F.Blake) L.B.Sm.	Flacourtiaceae	Leaf	Methanol	‐	In vitro	T.c	30 μg/ml	‐	Panama	(Calderón et al., 2010)
Lycium cuneatum Dammer	Solanaceae	Aerial parts	Ethanol	‐	In vitro	T.c	29 μg/ml	‐	Panama	(Calderón et al., 2010)
Maianthemum paludicola LaFrankie	Convallariaceae	Whole plants	Methanol	‐	In vitro	T.c	5 μg/ml	‐	Panama	(Calderón et al., 2010)
Mandevilla antennacea (A.DC.) K.Schum.	Apocynaceae	Leaves stems	Ethanol	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Marrubium vulgare subsp. apulum (Ten.) H.Lindb.	Lamiaceae	Aerial parts	Methanol	‐	In vitro	T.c	22.66 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Matayba guianensis Aubl.	Sapindaceae	Stems bark	Hexane	‐	In vitro	T.c	17.8 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Miconia buxifolia Naudin	Melastomataceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Mikania periplocifolia Hook. & Arn.	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Munnozia maronii (André) H.Rob.	Asteraceae	Leaves	Ethanol	‐	In vitro	T.c	25 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Myrsine guianensis (Aubl.) Kuntze	Myrsinaceae	Leaves	Hexane	‐	In vitro	T.c	65.0 μg/ml	107.1 μg/ml	Brazil	(Charneau et al., 2016)
Myrcianthes rhopaloides (Kunth) McVaugh	Myrtaceae	Leaves	Methanol	‐	In vitro	T.c	24 μg/ml	‐	Panama	(Calderón et al., 2010)
Nicotiana glauca var. angustifolia Comes	Solanaceae	Aerial parts	Methanol	‐	In vitro	T.c	38 μg/ml	‐	Panama	(Calderón et al., 2010)
Paeonia lactiflora var. lactiflora	Paeoniaceae	Root	Water	‐	In vitro	T.c	27.9 μg/ml	‐	Argentina	(Schinella et al., 2002)
Parthenium hysterophorus L.	Asteraceae	Leaves	DCM	Ambrosin	In vitro	T.b.b	67.1 μg/ml	11.46 μg/ml	Mexico	(Sepúlveda‐Robles et al., 2019)
Parietaria debilis var. ceratosantha Wedd.	Urticaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Paullinia clavigera Schltdl.	Sapindaceae	Bark	Chloroform	‐	In vitro	T.c	100%	‐	Peru	(González‐Coloma et al., 2012)
Persea americana var. americana	Lauraceae	Leaf	Methanol	‐	In vitro	T.c	65.51 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Phellodendron amurense var. sachalinense F. Schmidt	Rutaceae	Root bark	Methanol	‐	In vitro	T.c	11.3 μg/ml	‐	Argentina	(Schinella et al., 2002)
Phyla betulifolia (Kunth) Greene	Verbenaceae	Whole plant	Methanol	‐	In vitro	T.c	30 μg/ml	‐	Panama	(Calderón et al., 2010)
Phytolacca bogotensis Kunth	Phytolaccaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Phytolacca tetramera Hauman	Phytolaccaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper acutifolium Ruiz & Pav.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	39 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper aduncum var. brachyarthrum (Trel.) Yunck.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	38 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper aeruginosibaccum Trel.	Piperaceae	Leaf	Ethanol	‐	In vitro	T.c	12 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper barbatum var. andicolum (Kunth) Trel. & Yunck.	Piperaceae	Leaf	Ethanol	‐	In vitro	T.c	10 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper dilatatum f. dilatatifolium (Trel. & Yunck.) Steyerm.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	31 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper elongatum var. brachyarthrum Trel.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	36 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper glabratum Kunth	Piperaceae	Leaf	DCM	‐	In vitro	T.c	25 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper hispidum var. gamboanum C. DC.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	26 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper holtonii var. parvispicum Yunck.	Piperaceae	Root	Ethanol	‐	In vitro	T.c	10 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper longestylosum C. DC.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper abalienatum Trel.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	35 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper rusbyi C. DC.	Piperaceae	Leaf	DCM	‐	In vitro	T.c	32 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper scabrum Willd. ex Kunth	Piperaceae	Leaf	Ethanol	‐	In vitro	T.c	32 μg/ml	‐	Panama	(Calderón et al., 2010)
Piper umbellatum var. glabrum C. DC.	Piperaceae	Leaf	Ethanol	‐	In vitro	T.c	25 μg/ml	‐	Panama	(Calderón et al., 2010)
Podanthus ovatifolius Lag.	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	40.1 μg/ml	‐	Chile	(Muñoz et al., 2013)
Polygonum acuminatum Kunth	Polygonaceae	Leaf	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Polygonum ferrugineum var. patagonicum (Speg.) Macloskie	Polygonaceae	Aerial parts	Methanol	‐	In vitro	T.c	37 μg/ml	‐	Panama	(Calderón et al., 2010)
Poria cocos L.	Polyporaceae	Sclerotium	Ethanol	‐	In vitro	T.c	16.8 μg/ml	‐	Argentina	(Schinella et al., 2002)
Pouteria gardneri (Mart. & Eichler ex Miq.) Baehni	Sapindaceae	Roots woods	Hexane	‐	In vitro	T.c	45.5 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Piscidia carthagenensis Jacq.	Fabaceae	Aerial parts	Methanol	‐	In vitro	T.c	28 μg/ml	‐	Panama	(Calderón et al., 2010)
Psidium laruotteanum Cambess	‎Myrtaceae	Leaves	Hexane	‐	In vitro	T.b.r	3.9 μg/ml	>100 μg/ml	Brazil	(Charneau et al., 2016)
Psittacanthus cordatus (Hoffmanns. ex Schult. f.) Blume	Loranthaceae	Leaf	Ethanol	‐	In vitro	T.c	40 μg/ml	‐	Panama	(Calderón et al., 2010)
Ranunculus sceleratus subsp. multifidus (Nutt.) Hultén	Renonculaceae	Aerial parts	Ethanol	‐	In vitro	T.c	0.7 μg/ml	18.7 μg/ml	Argentina	(Schinella et al., 2002)
Rauvolfia tetraphylla L.	Apocynaceae	Root	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Rehmania glutinosa L.	Oronbanchaceae	Root	Ethanol	‐	In vitro	T.c	24.5 μg/ml	‐	Argentina	(Schinella et al., 2002)
Ruta chalepensis L.	Rutaceae	Leaf	Methanol	‐	In vitro	T.c	72.30 μg/ml	‐	Mexico	(Molina‐Garza et al., 2014)
Salvertia convallariodora A. St.‐Hil.	Vochysiaceae	Leaves	Hexane	‐	In vitro	T.b.g	35.4 μg/ml	>100 μg/ml	Brazil	(Charneau et al., 2016)
Schinus molle var. areira (L.) DC.	Anarcadiaceae	Leaves	Methanol	‐	In vitro	T.c	16.31 μg/ml		Mexico	(Molina‐Garza et al., 2014)
Scoparia dulcis L.	Scrophulariaceae	Whole plants	Ethanol	‐	In vitro	T.c	4 μg/ml	‐	Panama	(Calderón et al., 2010)
Scrophularia auriculata L.	Scrofulariaceaes	Aerial parts	Ethanol	‐	In vitro	T.c	23.3 μg/ml	‐	Argentina	(Schinella et al., 2002)
Scutellaria baicalensis f. albiflora H.W.Jen & Y.J.Chang	Lamiaceae	Root	Methanol	‐	In vitro	T.c	7.5 μg/ml	28.7 μg/ml	Argentina	(Schinella et al., 2002)
Sebastiania brasiliensis var. anisophylla Müll.Arg.	Euphorbiaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Sebastiania commersoniana (Baill.) L.B.Sm. & Downs	Euphorbiaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Solidago chilensis var. chilensis	Asteraceae	Leaves	Methanol	‐	In vitro	T.c	32 μg/ml	‐	Panama	(Calderón et al., 2010)
Sapranthus viridiflorus G.E. Schatz	Annonaceae	Aerial parts	Methanol	‐	In vitro	T.c	25 μg/ml	‐	Panama	(Calderón et al., 2010)
Sarcostemma gracile Decne.	Asclepiadaceae	Aerial parts	Ethanol	‐	In vitro	T.c	42 μg/ml	‐	Panama	(Calderón et al., 2010)
Schinus molle var. areira (L.) DC.	Anacardiaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Solanum actaeibotrys Rusby	Solanaceae	Leaves	Ethanol	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Solanum cornifolium Dunal	Solanaceae	Leaf	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Srevia yaconensis L.	Asteraceae	Woods	Ethanol	‐	In vitro	T.c	50 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Styrax conterminus Donn.Sm.	Styracaceae	Bark	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Tabebuia serratifolia (Vahl) G.Nicholson	Bignoniaceae	Bark	Hexane	‐	In vitro	T.c	100 μg/ml	‐	Peru	(González‐Coloma et al., 2012)
Tagetes caracasana Humb. ex Willd.	Asteraceae	Leaves	Oil	‐	In vitro	T.c	4.56 μg/ml	25.73 μg/ml	Brazil	(Escobar et al., 2009)
Tagetes filifolia subsp. filifolia	Asteraceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Tagetes heterocarpha Rydb.	Asteraceae	Leaves	Oil	‐	In vitro	T.c	12.84 μg/ml	43.03 μg/ml	Brazil	(Escobar et al., 2009)
Tagetes lucida f. florida (Sweet) Voss	Asteraceae	Leaves	Oil	‐	In vitro	T.c	18.94 μg/ml	>300 μg/ml	Brazil	(Escobar et al., 2009)
Tagetes zypaquirensis Bonpl.	Asteraceae	Leaves	Oil	‐	In vitro	T.c	21.30 μg/ml	126.40 μg/ml	Brazil	(Escobar et al., 2009)
Terminalia triflora (Griseb.) Lillo	Combretaceae	Aerial parts	Methanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Tradescantia zebrina var. flocculosa (G.Brückn.) D.R.Hunt	Commelinaceae	Aerial parts	Hexane	‐	In vitro	T.c	96%	‐	Peru	(González‐Coloma et al., 2012)
Tynanthus guatemalensis Donn.Sm	Bignoniaceae	Stems	Ethanol	‐	In vitro	T.c	> 50 μg/ml	‐	Panama	(Calderón et al., 2010)
Vatairea macrocarpa var. cinerascens (Benth.) Ducke	Fabaceae	Roots woods	Hexane	‐	In vitro	T.c	32.6 μg/ml	>100 μg/ml	Brazil	(Charneau et al., 2016)
Vernonia squamulosa Hook. & Arn.	Asteraceae	Leaves	Petroleum	‐	In vitro	T.c	100 μg/ml	‐	Bolivia	(Fournet et al., 1994)
Xylopia aromatica (Lam.) Mart.	Annonaceae	Root woods	Hexane	‐	In vitro	T.c	21.6 μg/ml	‐	Brazil	(Mesquita et al., 2005)
Zamia ulei subsp. lecointei (Ducke) Ducke	Zamiaceae	Underground tuberous stem	Chloroform	‐	In vitro	T.c	92.5%	‐	Peru	(González‐Coloma et al., 2012)
Zanthoxylum chiloperone var. angustifolium Engl.	Rutaceae	Aerial parts	Alkaloidal	canthin‐6‐one	In vivo	T.c in Balb/c mice, 5 mg/kg/day	80–100% inhibition	‐	Paraguay	(Ferreira et al., 2007)
Ziziphus mistol Griseb.	Rhamnaceae	Leaf	Ethanol	‐	In vitro	T.c	25 μg/ml	‐	Panama	(Calderón et al., 2010)
Zuccagnia punctata Cav.	Fabaceae	Leaf	Ethanol	‐	In vitro	T.c	20 μg/ml	‐	Panama	(Calderón et al., 2010)

FIGURE 5.

Chemical structures of isolated compounds from Latin America medicinal plants

3.7. North America

A total of 29 plants have been identified in the literature. Interestingly, the lack of testing against T. cruzi, which is prevalent in the southern part of North America, was observed in this study. The plants showed excellent anti‐trypanosomal activity with a minimum inhibitory concentration of fewer than 10 µg/ml. The crude extracts of Nuphar luteum (0.42 µg/ml), Hoita macrostachya (0.48 µg/ml) and Rhus integrifolia (0.50 µg/ml) showed the highest activity against Trypanosoma brucei (Table 6).

TABLE 6.

Plants assessed for anti‐trypanosomal application for which the EC50 values are known

Scientific name	Family	Part(s) used	Solvent	Bioactive compound	Model	Sub species	EC50	CC50	Country	References
Acer rubrum subsp. carolinianum (Walter) W.Stone	Sapindaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.88 μg/ml	‐	USA	(Jain et al., 2016)
Alnus rubra f. pinnatisecta (Starker) Rehder	Betulaceae	Bark	Ethanol	‐	In vitro	T.b.b	0.94 μg/ml	‐	USA	(Jain et al., 2016)
Anogeissus leiocarpus (DC.) Guill. & Perr.	Combretaceae	Root bark	Methanol	‐	In vitro	T.b.b	0.82 μg/ml	‐	USA	(Kenguele, 2009)
Arctostaphylos viscida subsp. mariposa (Dudley) P.V.Wells	Ericaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.88 μg/ml	‐	USA	(Jain et al., 2016)
Boykinia major var. intermedia (A.Heller) Piper	Saxifragaceae	Root	Ethanol	‐	In vitro	T.b.b	2.82 μg/ml	‐	USA	(Jain et al., 2016)
Chrysolepis chrysophylla (Douglas ex Hook.) Hjelmq.	Fagaceae	Flowers	Ethanol	‐	In vitro	T.b.b	2.89 μg/ml	‐	USA	(Jain et al., 2016)
Coccoloba pubescens L.	Polygonaceae	Stems	Ethanol	‐	In vitro	T.b.b	0.83 μg/ml	‐	USA	(Jain et al., 2016)
Eriogonum fasciculatum var. polifolium (Benth.) Torr. & A.Gray	Polygonaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.68 μg/ml	‐	USA	(Jain et al., 2016)
Eriogonum umbellatum subsp. dumosum (Greene) S.Stokes	Polygonaceae	Leaf stems	Ethanol	‐	In vitro	T.b.b	2.79 μg/ml	‐	USA	(Jain et al., 2016)
Eucalyptus citriodora Hook.	Myrtaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.91 μg/ml	‐	USA	(Jain et al., 2016)
Fagara zanthoxyloides Lam.	Rutaceae	Bark	Methanol	‐	In vitro	T.b.b	6.42 μg/ml	‐	USA	(Kenguele, 2009)
Hamamelis virginiana f. parvifolia (Nutt.) Fernald	Hamamelidaceae	Stem	Ethanol	‐	In vitro	T.b.b	2.54 μg/ml	‐	USA	(Jain et al., 2016)
Hoita macrostachya (DC.) Rydb.	Fabaceae	Leaf	Ethanol	‐	In vitro	T.b.b	0.48 μg/ml	‐	USA	(Jain et al., 2016)
Juniperus communis subsp. alpina (Schoop, Büechi et al.) Celak.	Cupressaceae	Leaf stem	Ethanol	‐	In vitro	T.b.b	2.40 μg/ml	‐	USA	(Jain et al., 2016)
Leea rubra Blume ex Spreng.	Vitaceae	Stem	Ethanol	‐	In vitro	T.b.b	1.62 μg/ml	‐	USA	(Jain et al., 2016)
Lepechinia calycina var. glabella (A.Gray) Epling ex Munz	Lamiaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.50 μg/ml	‐	USA	(Jain et al., 2016)
Ligustrum sinense var. myrianthum (Diels) Hoefker	Oleaceae	Leaf fruit	Ethanol	‐	In vitro	T.b.b	2.77 μg/ml	‐	USA	(Jain et al., 2016)
Lyonia fruticosa (Michx.) G.S. Torr.	Ericaceae	Stems	Ethanol	‐	In vitro	T.b.b	2.54 μg/ml	‐	USA	(Jain et al., 2016)
Medinilla magnifica Lindl.	Melastomataceae	Flowers fruit	Ethanol	‐	In vitro	T.b.b	2.25 μg/ml	‐	USA	(Jain et al., 2016)
Nuphar lutea subsp. advena Kartesz & Gandhi	Nymphaeaceae	Fruit	Ethanol	‐	In vitro	T.b.b	0.42 μg/ml	‐	USA	(Jain et al., 2016)
Quercus alba f. latiloba (Sarg.) E.J.Palmer & Steyerm.	Fagaceae	Bark	Ethanol	‐	In vitro	T.b.b	1.92 μg/ml	‐	USA	(Jain et al., 2016)
Pseudocedrela kotschyi (Schweinf.) Harms	Meliaceae	Root	Methanol	‐	In vitro	T.b.b	8.94 μg/ml	‐	USA	(Kenguele, 2009)
Rhododendron occidentale (Torr. & A. Gray) A. Gray	Ericaceae	Leaf	Ethanol	‐	In vitro	T.b.b	2.87 μg/ml	‐	USA	(Jain et al., 2016)
Rhus integrifolia (Nutt.) Benth. & Hook. f. ex Rothr.	Anacardiaceae	Leaf	Ethanol	‐	In vitro	T.b.b	0.50 μg/ml	‐	USA	(Jain et al., 2016)
Ribes montigenum McClatchie	Grossulariaceae	Stems	Ethanol	‐	In vitro	T.b.b	1.94 μg/ml	‐	USA	(Jain et al., 2016)
Ribes speciosum Pursh	Grossulariaceae	Leaf stems flowers	Ethanol	‐	In vitro	T.b.b	2.95 μg/ml	‐	USA	(Jain et al., 2016)
Sabal minor (Jacq.) Pers.	Arecaceae	Flowers	Ethanol	‐	In vitro	T.b.b	1.06 μg/ml	‐	USA	(Jain et al., 2016)
Salvia spathacea Greene	Lamiaceae	Stems	Ethanol	‐	In vitro	T.b.b	1.13 μg/ml	‐	USA	(Jain et al., 2016)
Terminalia glaucescens Planch. ex Benth.	Combretaceae	Root	Methanol	‐	In vitro	T.b.b	9.04 μg/ml	‐	USA	(Kenguele, 2009)

3.8. Oceania plants

Few studies have been found in the literature about the medicinal plants from Oceania with anti‐trypanosomal activity. This corroborates with the scientometric analysis of global trypanosomiases research from 1988 to 2017 which shows that Oceania researchers have contributed less than the others to trypanosomiases research in this region (Hassan et al., 2020). Only seven plants have been identified in the literature, of which just Corydalis crispa (4.63 µg/ml) showed activity against Trypanosoma brucei (Table 7).

TABLE 7.

Plants assessed for anti‐trypanosomal activity

Scientific Name	Family	Part (s) used	Solvent	Bioactive compound	Model	Sub species	EC50	CC50	Country	References
Aconitum laciniatum (Brühl) Stapf	Ranunculaceae	Leaf	Methanol	‐	In vitro	T.b.b	>25 μg/ml	>25 μg/ml	Australia	(Wangchuk, 2014)
Ajania nubigena (Wall.) C.Shih	Compositae	Leaf	Methanol	‐	In vitro	T.b.b	>10 μg/ml	>10 μg/ml	Australia	(Wangchuk, 2014)
Codonopsis bhutanica Ludlow	Campanulaceae	Leaf	Methanol	‐	In vitro	T.b.b	>5 μg/ml	>5 μg/ml	Australia	(Wangchuk, 2014)
Corydalis crispa var. laeviangula C.Y.Wu & H.Chuang	Fumariaceae	Leaf	Methanol	‐	In vitro	T.b.b	4.63 μg/ml	12.5 μg/ml	Australia	(Wangchuk, 2014)
Corydalis dubia Prain	Fumariaceae	Leaf	Methanol	‐	In vitro	T.b.b	>10 μg/ml	>10 μg/ml	Australia	(Wangchuk, 2014)
Meconopsis simplicifolia (D. Don) Walp.	Papaveraceae	Leaf	Methanol	‐	In vitro	T.b.b	>10 μg/ml	>10 μg/ml	Australia	(Wangchuk, 2014)
Pleurospermum amabile W. G. Craib & W.W. Sm.	Umbellifereae	Leaf	DCM	‐	In vitro	T.b.b	14.83 μg/ml	>25 μg/ml	Australia	(Wangchuk, 2014)

Note: Their EC50 values are known.

Many plants worldwide serve as a potential source of bioactive compounds against trypanosomiases. We encountered 77 chemically defined natural molecules reported in the literature, which have been evaluated for anti‐trypanosomal activity. Fifty‐nine were from Africa, 11 from Asia, 3 from Europe and 4 from Latin America. The active compounds, isolated and identified, belong to the classes of alkaloids, triterpenoids, lactones (Kohno, et al., 2010), quinoids, flavonoids, steroids, lipids, iridoids, oxygen heterocycles, benzenoids, lignans, proteids, coumarins, phenylpropanoids and peptides. The most active compounds with EC50 of <20 µg/ml are abruquinones, letestuianin, 22‐hydroxyclerosterol, 7,15‐dihydroxy‐7,15‐deoxo nimbin, cassythine, polyacetylenes (MS‐1, MS‐2 and MS‐4), Putranoside A, kolavenol, triterpenoid (3β,13β‐dihydroxy‐urs‐11‐en‐28‐oic acid), lucidamine, oleanolic acid, phytol, betulinic acid, β‐sitosterol, citronellal, clerodane, saringosterol, 24‐hydroperoxy‐24‐vinylcholesterol, melicopicine, skimmianine, α‐amyrin, punicalagin, cedrelone, vernogui‐nosterol and diacetylvernoguinosterol, cynaropicrin, Schkuhrin I and II, saropeptide, oregonin, hirsutanone, curlone, isoiridogermanal, mahanimbine, murrayafoline, girinimbine, vanicoside E, (+)‐ketopinoresinol, isorhamnetin, cardamomin, onopordopicrin, juncunol, miltirone, isoobtusi‐lactone A, canthin‐6‐one, thus, are promising leads for drug development. Abruquinone K, L, A and D, artemisinin, MS‐2, MS‐4, dioncophylline E, dihydrochelerythrine, clerodane, Schkuhrin I, cynaropicrin, waltheriones L and vanicoside E showed inhibitory activity below 1 µg/ml or 1 µM.

According to the standards of the National Cancer Institute (NCI), a crude extract can be considered active for an EC50 ≤ 20 µg/ml (Cordell et al., 1993). Hence, most plant extracts (more than 50%) showed activity below 20 µg/ml. We highlighted the plant extracts that have the most activity below 1 µg/ml, which include Kanahia laniflora, Arctium nemorosum, Crinum stuhlmannii subsp. Delagoense, Myristica fatua, Narcissus broussonetii var. grandiflorus, Salvia miltiorrhiza var. charbonnelii, Anthemis tinctoria subsp. australis, Casearia sylvestris var. lingua, Ranunculus sceleratus subsp. Multifidus, Alnus rubra f. pinnatisecta, Anogeissus leiocarpus, Coccoloba pubescens, Hoita macrostachya, Nuphar lutea subsp. Advena, Rhus integrifolia. All active extracts belong to different families and are from different parts of the plant. Hence, it was impossible to mention the particular plant parts or specific family.

Artemisinin is an endoperoxide sesquiterpene lactone isolated from Artemisia annua, one of the well‐known antiparasitic and anti‐tumoural chemotherapeutic agents (Rocha et al., 2005). The impacts of Artemisinin and its derivatives on Trypanosoma parasites have been investigated in in vitro and animal models. These compounds effectively inhibit the metabolism of parasites, while exhibiting limited side effects on the host (Loo et al., 2017). A large number of in vitro and in vivo studies on amastigotes, epimastigotes and trypomastigotes of Trypanosoma have displayed that artemisinin and its derivatives have pharmacological activities in controlling the parasites and have shown significant impact against protozoans such as T. brucei rhodesiense, T. brucei brucei and T. cruzi (Loo et al., 2017).

3.9. Critical assessment of the literature information embodied in the present study

Africa, Asia and the Middle East flore provide many promising plants, but further in vivo studies are required to confirm their application as anti‐trypanosomal agents. It is worth noting that before in vivo studies, the in vitro biological activity should be accompanied by cytotoxicity studies against mammalian cells, followed by pharmacokinetic studies. On the other hand, some literature was not entered into this systematic review based on mesh terms. In West Africa and South America, Trypanosoma vivax is at the helm of the majority of trypanosome infections in cattle and other ruminants. This pathogen is not well established in laboratory animals, and investigation into pathogenic isolates has been restricted by the difficulty of its in vitro establishment. In this study, very few compounds were screened against Trypanosoma vivax (Isoun and Isoun, 1974' Cortez et al., 2006).

4. CONCLUSIONS

Many plants worldwide serve as a potential source of bioactive compounds against trypanosomiases. Africa, Asia and the Middle East flore provide many promising plants, but further in vivo studies are required to confirm their application as anti‐trypanosomal agents. At the same time, the isolation of the bioactive compounds in their pure form should be pursued. Further vital investigations, including clarification of their mode of action, assessment of the efficacy of several bioactive compounds and their toxicity profile, need to be carried out.

AUTHOR CONTRIBUTIONS

Shahin Nekoui: Methodology; writing – review & editing. Faham Khamesipour: Investigation; supervision; validation; writing – original draft; writing – review & editing. Pardis Mohammadi Pour: Methodology; writing – review & editing.

CONFLICT OF INTEREST

The authors declare that they have no competing interests.

FUNDING

No funding was received.

ETHICS STATEMENT

An ethics statement is not applicable because this study is based exclusively on published literature.

PEER REVIEW

I would not like my name to appear with my report on Publons https://publons.com/publon/10.1002/vms3.912

Nekoei, S. , Khamesipour, F. , Habtemariam, S. , de Souza, W. , Mohammadi Pour, P. , & Hosseini, S. R. (2022). The anti‐Trypanosoma activities of medicinal plants: A systematic review of the literature. Veterinary Medicine and Science, 8, 2738–2772. 10.1002/vms3.912

DATA AVAILABILITY STATEMENT

Data sharing is not applicable to this article as no new data were created or analysed in this study.