Anti-Infective and Anti-Cancer Properties of the Annona Species: Their Ethnomedicinal Uses, Alkaloid Diversity, and Pharmacological Activities

Abstract

Annona species have been a valuable source of anti-infective and anticancer agents. However, only limited evaluations of their alkaloids have been carried out. This review collates and evaluates the biological data from extracts and purified isolates for their anti-infective and anti-cancer activities. An isoquinoline backbone is a major structural alkaloid moiety of the Annona genus, and more than 83 alkaloids have been isolated from this genus alone. Crude extracts of Annona genus are reported with moderate activities against Plasmodium falciparum showing larvicidal activities. However, no pure compounds from the Annona genus were tested against the parasite. The methanol extract of Annona muricata showed apparent antimicrobial activities. The isolated alkaloids from this genus including liriodenine, anonaine, asimilobine showed sensitivity against Staphylococcus epidermidis. Other alkaloids such as (+)-Xylopine and isocoreximine indicated significant anti-cancer activity against A549 and K-562 cell lines, respectively. This review revealed that the alkaloids from Annona genus are rich in structural diversity and pharmacological activities. Further exploration of this genus and their alkaloids has potential for developing novel anti-infective and anticancer drugs.

1. Introduction

Annona is one of the 129 genera of the Annonaceae family and contains 119 species with eight species grown for commercial uses [1,2]. Most of the species grow in tropical regions; e.g., the soursop fruit tree (Annona muricata) is cultivated commercially and is widespread in the West Indies, North and South Americas, Africa, the Pacific Islands, and Southeast Asia. Annona species have been used as medicines by indigenous people for a wide range of disorders including parasitic infections, inflammation, diabetes, and cancer [3]. The phytochemical investigation of this plant genus has revealed the presence of acetogenins, alkaloids, essential oils, flavonoids, terpenoids, and other chemical classes [4,5]. Acetogenins (ACGs) are the major constituents of the Annona genre and examples were found to possess a variety of pharmacological properties including as antitumor, immunosuppressive, pesticidal, antiprotozoal, antimicrobial, antimalarial, anthelmintic, and antiviral agents, with some being commercially developed for the treatment of oral herpes and treating infestations of head lice, fleas, and ticks [5,6]. However, the available phytochemistry, including information on the composition and bioactivities of constituents from Annona species is limited and scattered [2]. This review evaluates the ethnopharmacological uses, alkaloid constituents, and the anti-infective properties of constituents contained within the genus Annona.

2. Ethnomedicinal Uses of Anonna Genus

The Annona species are moderately erect shrubs or small trees that grow to 5–11 m in height depending upon species and the region they inhabit, and are ferruginous to greyish, and tomentose when young, but later becoming glabrous [7]. Ethnobotanically, the plants from this genus play significant roles as food products and medicinal agents. A recent review on A. muricata showed that it is widely used in traditional decoctions in as many as 35 different countries for treating numerous diseases [8]; e.g., despite reports that the seed is toxic, traditional Mexican pharmacopeia uses powdered toasted seed as a potent emetic and cathartic. The seed was also used as an insecticidal agent and seed powder was used as a lotion when mixed with grease to treat parasitic skin disorders. A decoction of the fruit skin was used to treat pneumonia [9]. To South-East Asian people, decocted leaves of Annona reticulate (“custard apple”) was used internally against worms, and poultice leaves were applied externally to treat abscesses, boils, and ulcers. Unripe fruit was used to treat diarrhea and dysentery, and decocted root was used as febrifuge and to treat toothache [9,10].

In India, Annona squamosa (“sugar apple”) leaves are crushed and applied to wounds, ulcers, and is sniffed to relieve hysteria and fainting spells. Decocted leaves are used systemically to treat dysentery (India), and as a tonic, febrifuge, and cold remedy (tropical America). Crushed ripe fruit was applied to surface tumors (India), whereas the unripe fruit was used to treat dysentery in Elsavador [9]. The stem bark and root were used to treat diarrhea and dysentery [9]. The Annona muricata (“soursop”) has been used in the indigenous medicine of Togo to treat hypertension and diabetes mellitus [11], with the leaves used as an anti-parasitic, anti-rheumatic, astringent, and emetic in Brazil [12]. Decocted leaves were used as an analgesic, antispasmodic agents in Equador, whereas it is used as a remedy for cough, catarrhal inflammation, diarrhea, dysentery, bladder problems, and inflammation in the West Indies. Mashed leaves were also used as a poultice to relief eczema, rheumatism, and skin eruptions [9]. Traditional medicine in Indonesia has used the leaves as a treatment for boils, spasms, and as an aphrodisiac [13]. The fruit juice was used as a diuretic agent and to treat leprosy and liver ailments [9]. Currently, in Indonesia, the fruit is commonly used traditionally to treat breast cancer. A decoction of the seeds was used as a strong emetic agent, and the flower was used to treat catarrhal inflammation. In Materia Medica of British Guiana, a tincture of the powdered seeds and bay rum serves as a strong emetic. Soursop flowers are believed to alleviate catarrhal inflammation. The roots have been used as a vermifuge and an antidote for poisoning [9]. The roots are commonly used in Guinea as anti-parasitic and pesticidal agents. In Indonesia, currently, the stem and root bark are used as an alternative medication to treat malarial fever.

There are less popular Annona species, which were also used in traditional medication. In Guyana, a decoction of the stem bark of A. ambotay Aublet was used to treat ulcers and skin eruptions. Mixed with the bark, the leaf was used as febrifuge and sudorific. A tea made of the stem and leaf of A. glabra L. was consumed to eliminate flatworm and nematodes in Guyana. A decoction of the bark of Annona haematantha Miq. was used as a bath to treat skin ulcers, while its syrup was used to relieve cough. The bark infusion of Annona sericea Dunal was used to treat cramps [14]. In Mexico, the leaf of Annona diversifolia Safford (“Ilama”) was commonly used as an anticonvulsant, anti-inflammatory, and analgesic agent [15]. An infusion of the leaves of A. senegalensis (“wild custard apple”) was used to treat diarrhea and pulmonary complaints. Decocted stem bark was used to treat stomachache, toothache, dysentery, and worm infection. The root was used to treat venereal diseases and intestinal problems, snake bites, and as cancer therapy (Nigeria). Its green fruits was used to treat Guinea worm sores, diarrhea, dysentery [9]. In Brazil, Annona salzmanii A. DC has been used to treat dysentery, ulcers, and inflammation [16].

3. Phytochemical Studies of Secondary Metabolites of Annona Genus

The juicy pulp of the fruit is often a good source of sugar, vitamins, minerals, and phenolic intake. For example, the dried pulp of Annona muricata contains 68% sugars for every 100 g containing 1.0 g protein, 0.97 g fat, 1.28 niacin, and 29 mg ascorbic acid. Moreover, it could supply 3 g of phenolic substances for every 100 g of pulp [9,17]. The 20th century reported preliminary examinations of the Annona plants of the leaves, fruits, and seeds. Since the 1980s, with the advent of pursuing anti-cancer drug leads from medicinal plants, acetogenin was isolated from the Annona genus based on its promising anti-cancer activity. For example, a recent acetogenin, squamocin P, isolated from A. squamosa, possessed significant anticancer activity against SMMC 7721/T, MCF-7/ADR, A549/T with IC₅₀ values of 0.435, 3.34, 6.32 µM, respectively, with the positive control cisplatin having higher IC₅₀ values of 198.85, 178.87, and 219.33 µM against SMMC 7721/T, MCF-7/ADR, and A549/T, respectively. While this encouraged investigations into this species, they were confined to this one polyketide compound, at the expense of other components present. Figure 1a shows the number of compounds isolated from each plant part of Annona muricata. In the previous phytochemical studies of Annona muricata, around 127 compounds were isolated, in which almost 90% were acetogenins (Figure 1b) [18].

Figure 1.

Phytochemical study on Annona muricata. (a) Number of isolated compounds in different regions of the plants; (b) comparison between total isolated acetogenins and alkaloids.

Acetogenins from the Annona genus were reviewed together with other genus in the same family Annonaceae [8,19,20,21,22,23], which covered the isolation, molecular properties, and biosynthesis of their pharmacological activities. Here, we collected records on alkaloids which were isolated in the Annona plant genus from 1960–2019 (Table 1). The alkaloids present have been of interest since the first, annonaine (8, Figure 2), was isolated in 1931 from the stem bark of Annona muricata L. collected in the Philippines [24]. Table 1 shows the alkaloids isolated from the specific plants of each species and their structures are presented in Figure 2.

Table 1.

Alkaloid Constituents of Annona.

Plant Parts	Location	Isolated Alkaloids
Annona ambotay
Wood	Brazil	benzene-EtOH: cleistopholine 1, dielsinol 2, dielsiquinone 3, geovanine 4, kinabaline 5, 6-methoxyonychine 6, onychine 7 [25]
Annona cherimola
Leaves	Brazil	(−)-anonaine 8, (−)-asimilobine 9, lanuginosine 10, liriodenine 11, lysicamine 12, pronuciferine 13, (+)-stepharine 14 [26]
Leaves	India	Phanostenine 15 [27]
Leaves	Spain	(−)-anonaine 8, (+)-corytuberine 16, (+)-isoboldine 17, lanuginosine 10, liriodenine 11, (+)-nornantenine 18, (+)-reticuline 19, (−)-stepholidine 20 [28]
Seeds	Spain	(−)-anonaine 8, cleistopholine 1, lanuginosine 10, liriodenine or xoushinsunine 11 [29,30]
Stem	Taiwan	(+)-annocherine A 21, (+)-annocherine B 22, (−)-artabonatine B 23, cherianoine 24, cherimoline 25, (−)-romucosine H 26 [31,32]
Stem	Spain	(−)-anolobine 27, (+)-anonaine 28, (−)-asimilobine 9, (−)-corydine 29, (−)-corypalmine 30, (−)-discretamine 31, (+)-glaziovine 32, (+)-isoboldine 17, lanuginosine 10, liriodenine 11, lysicamine 12, (−)-N-methylasimilobine 33, (−)-norushinsunine 34, (−)-nuciferine 35, (−)-stepholidine 20, (−)-tetrahydropalmatine 36, (−)-xylopine 37, (+)-reticuline 19 [33]
Root	Mexico	(−)-corytenchine 38, (−)-isocoreximine 39 [34]
Annona diversifolia
Roots	Mexico	Liriodenine 11 [35]
Annona glabra
Fruit-stem	Taiwan	(−)-anonaine 8, annobraine 40, (−)-asimilobine 9, 1-aza-4-methyl-2-oxo-1,2-dihydro-9,10-anthracenedione 41, dehydrocorydalmine 42, (−)-N-formylanonaine 43, (−)-kikemanine 44, liriodenine 11, lysicamine 12, (−)-nornuciferine or (−)-N-methylasimilobine 33, (+)-nordomesticine 45, (+)-stepharine 14 [36]
Leaves	Mexico	(−)-anonaine 8, asimilobine 9, coreximine 46, (+)-reticuline 19 [37]
Leaves	Taiwan	(−)-N-methyl-actinodaphnine 47, (+)-reticuline 19 [38]
Root	Mexico	(−)-anonaine 8, (−)-asimilobine 9, (−)-coreximine 46, (−)-nornuciferine or (−)-N-methylasimilobine 33, (+)-reticuline 19 [37]
Stem	Mexico	(−)-anonaine 8, (−)-asimilobine 9, (−)-nornuciferine or (−)-N-methylasimilobine 33, (+)-reticuline 19 [37]
Stem	Taiwan	(−)-anolobine 27, (−)-anonaine 8, (−)-asimilobine 9, (+)-isoboldine 17, liriodenine (or oxoushinsunine) 11, (−)-N-nornuciferine 48, (−)-norushinsunine (or michelalbine) 34, (+)-reticuline 19, (−)-roemerine 49 [39,40]
Annona montana Macf (wild soursop)
Leaves	Taiwan	annolatine 50, annoretine 51, argentinine 52, liriodenine 11 [41]
Stem-Root bark	Guinea	Annomontine 53, (−)-anonaine 8, atherosperminine 54, (−)-asimilobine 9, (−)-coclaurine 55, (−)-coreximine 46, methoxyannomontine 56, oxoushinsunine or liriodenine 11, (+)-reticuline 19, (−)-xylopine 37 [42]
Stem bark	Japan	Annomontine 53 [43]
Annona muricata L. (soursop)
Leaves	Tanzania	(−)-anonaine 8, (−)-roemerine 49 [44]
	Japan	(−)-anonaine 8, (−)-annonamine 57, (+)-O,O-dimethylcoclaurine 58, (+)-4′-O-methylcoclaurine 59, (+)-norcorydine 60 [45]
Leaves	Guinea	(−)-anonaine 8, (−)-coclaurine 55, isolaureline 61, isoboldine 17, liriodenine 11, (+)-N-methylcoclaurine 62, norisolaurelin or (−)-xylopine 37, (−)-roemerine 49 [46,47]
Stem (bark)	Guinea	Anomurine 63, anomuricine 64, atherosperminine 54, (−)-coclaurine 55, (−)-coreximine 46, (+)-reticuline 19, (+)-stepharine 14 [48]
Roots	Indonesia	(−)-coclaurine 55, (+)-reticuline 19, argentinine 52, atherosperminine 54, (+)-xylopine 65 [18]
Annona paludosa Aubl.
Root bark	Guiena	(−)-anonaine 8, (−)-asimilobine 9, (−)-coreximine 46, dihydropalmatine 66, (+)-reticuline 19, (−)-scoulerine or (−)-discretamine 31, (−)-roemerine 49, (±)-tetrahydropalmatine 36 [49]
Annona reticulata
Leaves	Taiwan	(−)-asimilobine 9, (+)-corydine 67, (+)-glaucine 68, liriodenine 11, (+)-norcorydine 60, oxonantenine 69, oxoxylopine or lanuginosine 10, (−)-xylopine 37 [50]
Roots	Taiwan	(−)-aequaline or (−)-discretamine 31, (+/-)-annomontine 53, (−)-anonaine 8, (−)-asimilobine 9, (−)-3-hydroxynornuciferine 70, liriodenine 11, methoxyannomontine 56, (−)-michelalbine or (−)-norushinsunine 34, oxoushinsunine or liriodenine 11, (+)-reticuline 19 [51,52]
Annona salzmanii A. DC
Bark	Brazil	(−)-anonaine 8, (−)-asimilobine 9, cleistopholine 1, liriodenine 11, oxolaureline or 10-methoxyliriodenine 71, (+)- reticuline 19, (−)-xylopine 37 [16]
Annona sericea
Leaves		(−)-3-hydroxynornuciferine 70, (+)-isoboldine 17, (+)-N-methylcoclaurine 62, (+)-nornantenine 18, (−)-nornuciferine or (−)-N-methylasimilobine 33, oxonuciferine or lysicamine 12, (+)-reticuline 19 [53]
Annona squamosa
Leaves	Brazil	(−)-anonaine 8, asimilobine 9, liriodenine 11, (−)-nornuciferine or (−)-N-methylasimilobine 33, (+)-reticuline 19 [54]
Leaves- stem bark	Guinea	(−)-anonaine 8, (+)-coclaurine 72, (+)-isoboldine 17, liriodenine 11, (+)-nornuciferine 73, (−)-roemerine 49 [55,56]
Leaves	India	(−)-anonaine 8, (+)-corydine 67, (+)-glaucine 68, (+)-isocorydine 74, lanuginosine 10, (+)-O-methylarmepavine 75, (+)-norcorydine 60, norisocorydine 76, (−)-roemerine 49, (−)-xylopine 7 [57,58]
Leaves	Tanzania	(−)-anonaine 8,(−)-roemerine 49 [44]
Leaves	Zimbabwe	(−)-isocorydine 77, (−)-roemerine 49 [59]
Seeds	Brazil	(−)-anonaine 8, asimilobine 9, corypalmine 30, (−)-nornuciferine or (−)-N-methylasimilobine 33, (+)-reticuline 19 [54]
Stem	Taiwan	Annobraine 40, annosqualine 78, demethylsonodione 79, dihydroferuloyltyramine 80, dihydrosinapoyltyramine 81, liriodenine 11, squamolone 82, thalifoline 83 [60]
Roots	Taiwan	(−)-anolobine 27, (−)-anonaine 8, (−)-norushinsunine (or michelalbine) 34, oxoushinsuine (liriodenine) 11, (+)-reticuline 19 [61]

Figure 2.

Structures of Annona alkaloids (1–83).

4. Anti-Infective Alkaloids from the Genus Annona

Plants from the genus Annona plants have been used in traditional medication for the treatment of both infectious and non-infectious diseases. This led to the pharmacological and chemical screening of numerous species to confirm these pharmacological claims and to isolate the compounds which might be responsible for these activities. The Annona genus has been studied for activity against parasites, cancer, and as anti-oxidant agents.

4.1. Antiprotozoal Activities

Ethnopharmacological studies have revealed the Annona species Annona crassiflora, A. muricata, A. senegalensis, and A. squamosa were prescribed in malarial fever therapy. Further studies revealed leaf extract from A. crassiflora was rich in flavonoids and alkaloids, and was able to reduce the Plamsodium berghei NK65 infection level in mice by 57–75% with a daily dosage of 12.5 µg/kg/day [62]. Another study of the crude methanol extract of A. squamosa indicated moderate activity against Plasmodium falciparum 3D7 with an IC₅₀ value of 30 µg/mL compared to the chloroquine control, which gave an IC₅₀ value of 0.021 µg/mL [63]. Moderate anti-plasmodium activity was also shown using crude extracts of A. muricata (Table 2).

Table 2.

Anti-protozoal activity of several extract of Annona muricata and Annona reticulata [68,69].

Species	Part of Plant (Extract)	Anti-Protozoal Activity (IC50, µg/mL)
		Leishmania species			Trypanosoma cruzi	P. falciparum
		PH8	M2903	PP75		F32	W2
A. muricata	LF (Hexane)	100.0	>100.0	>100.0	100.0	7.2 a	38.6 a
	LF (EtOAc)	25.0	25.0	25.0	25.0	8.5 a	10.4 a
	LF (MeOH)	>100.0	>100	>100.0	100.0	9.2 a	36.8 a
	SD (Hexane)	98.6	76.3	83.1	74.9	11.4 a	38.2 a
	SD (EtOAc)	63.2	63.2	63.2	63.2	40.2 a	34.7 a
	SD (MeOH)	98.6	98.6	98.6	98.6	32.5 a	26.3 a
	PC (EtOH)						1.01
	PC (H2O)						>10
	PC (CH2Cl2)						0.94
	RT (EtOH)						0.79
	RT (H2O)						>10
	RT (CH2Cl2)						0.19
	ST(EtOH)						1.45
	ST (H2O)						>10
	ST (CH2Cl2)						3.32
A. reticulata	LF(EtOH)						>10
	LF (H2O)						>10
	LF (CH2Cl2)						>10
	TW (EtOH)						>10
	TW (H2O)						>10
	TW (CH2Cl2)						0.88
	ST(EtOH)						0.29
	ST (H2O)						>10
	ST (CH2Cl2)						0.82
	RT (EtOH)						1.90
	RT (H2O)						>10
	RT (CH2Cl2)						0.38
	FR (EtOH)						0.67
	RF (H2O)						>10
	RF (CH2Cl2)						0.42
Standard drug	Pentamidine	10.0	10.0	10.0
	Amphotericin B	0.2	0.2	0.2
	Bensoidazole				2.0
	Chloroquine					0.01	0.9
	Artemisisn						0.005

LF: leaf; SD: seed, PC: pericarp; RT: root; ST: stem bark; TW: twig; Leishmania amazonensis (PH8); Leishmania braziliensis (M2903); Leishmania donovani PP75; ^a Values represent percentage of inhibition at 10.0 µg/mL.

In an animal model test, an aqueous leaf extract of A. muricata showed a dose dependent antimalarial effect with the highest inhibition of 85.61% observed from a 1000 µg/kg dose. However, the treatment was unable to completely cure the mice, but prolonged the survival time [64]. An essential oil extract of A. squamosa demonstrated inhibition against the erythrocitic stages of P. falciparum, against epimastigotes forms of T. cruzi and against trypomastigotes forms of T. cruzi with IC₅₀ values of 14.7, 16.2, and 12.7 µg/mL, respectively [65].

Although there was a limited record regarding traditional uses of Annona plants to treat other parasitic protozoal infections, e.g., leishmaniasis and trypanosomiasis, several crude extracts of Annona plant (A. muricata) were also tested against L. amazonensis, L. braziliensis, L. Donovani, and T. cruzi (Table 2). The crude ethyl acetate extract from the leaves of A. muricata indicated potent activity against L. amazonensis, L. braziliensis, L. Donovani, and T. cruzi with IC₅₀ values of 10–25 µg/mL. A different strategy to control malarial infection involves controlling its vector. Past larvicidal studies have indicated that the crude methanol extract from the bark of A. squamosa resulted in 100% mortality of Anopheles subpictus (which carry human malaria parasites) at 500 µg/mL [66]. The extract from the stem and root bark were even more toxic toward malarial larvae (Anopheles gambiaes.s. Giles) with 50% mortality at 24 and 21 µg/mL, respectively [67].

The same protocol was applied to other disease vectors, including Aedes (dengue virus vector) and Culex (encephalitis virus). For example, the seeds of Annonas pecies were generally reported to be toxic with LC₅₀ values <1 µg/mL against both Aedes and Culex larvae (Table 3). These results demonstrated that the Annona plants can be used for controlling the vector especially in rural areas where modern, and likely more expensive, vector controls were limited.

Table 3.

Larvicidal of several extract of Annona genus [44,66,73,74,75,76].

Plant Name	Plant Extract	LC50 (µg/mL)
		Aedes aegypti	Aedes albopictus	Culex quinquefasciatus	Culex tritaeniorhynchus
A. crassiflora	SB (hexane)	192.57
	RW (hexane)	154.02
	RB (hexane)	264.15
	RB (EtOH)	0.71
	RW (EtOH)	8.94
	ST (EtOH)	16.1
A. glabra	SD (EtOH)	0.06
A. muricata	RT (EtOH)	42.3
	SD (hexane)	122.77
	SD (CHCl3)	0.90
	SD (MeOH)	85.91
	LF (MeOH)			56.47
A. senegalensis	LF (MeOH)			23.42
A. squamosal	RT (EtOH)	31.9
	LF (EtOH)	169	20.70
	SD (EtOH)	5.12	6.96
	LF (MeOH)		20.26	17.70
	SB (MeOH)				104.94

SB: stem bark; RB: root bark; RW: root wood; SD: seed; RT: root; LF: leaf.

Despite numerous alkaloids being isolated from Annona species, reports detailing pharmacological studies on single compounds remains limited. There are reports on the same alkaloids being isolated from different plant genus. For example, (+)-reticuline 19 was isolated from Croton linearis and was previously shown to possess a weak antriprotozoal activity against Lesihmania infatum with IC₅₀ values of 148.0 ± 1.2 µM [70]. Asimilobine 9 and isoboldine 17 isolated from the bark of Beilschmiedia alloiophylla (Costa Rica) possessed anti-leishmanial activity with IC₅₀ values of 29.8 ± 1.5 µM and 50.0 ± 4.0 µM, respectively [71]. A previous study on the leaves and fruits of Annona mucosa (Brazil) produced liriodenine 11, which was highly active against Leishmania amazonensis with an IC₅₀ value of 1.43 ± 0.58 μg/mL and was moderately active against Leishmania braziliensis with an IC₅₀ value of 55.92 ± 3.55 μg/mL [72].

4.2. Antimicrobial Activities

Traditionally, Annona plants have been prepared for use against infection related diseases, such as ulcer, dysentery, and boils, and therefore became a driving force for conducting anti-microbial studies against common bacteria; preliminary results on the crude extracts are shown in Table 4. In general, the crude extract possessed moderate to inactive anti-microbial values ranging from 6.25–4096 µg/mL. Most of the studies were based on the anti-microbial activity of crude extracts with no separate non-polar to polar fractions tested or individual constituents isolated. Therefore, further investigations are required to substantiate the traditional claims for these Annona plants by the isolation and identification of individual constituents. As a result, discussion here is confined to the anti-microbial activities from isolated alkaloid constituents (Table 5). A. muricata, A. squamosa, A. cherimola, and A. ambotay showed reasonable antimicrobial activities, whereas A. reticulata did not present antimicrobial activity, with reported MIC values of more than 1000 µg/mL against Bacillus cereus, Staphylococcus aureus [77]. Antimicrobial testing of the methanol extract of A. squamosa fruit against multidrug resistant MRSA reported MIC values of 5000 µg/mL, but no information was given against ESBLEC (extended-spectrum beta-lactamase producing E. coli), CRPA (carbapenem-resistant P. aeruginosa) and MDRAB (multidrug-resistant A. baumannii) [78]. The benzoquinoline alkaloid, anonaine 8, indicated comparable anti-microbial activities with positive control, with the exception against Staphylococcus aureus. Another study reported annoquinone A, isolated from A. Montana, possessed anti-microbial activity against Bacillus subtilis and Micrococcus luteus with IC₅₀ value of 10, 10 µg/mL, respectively [79].

Table 4.

Anti-microbial activities of crude extracts or fractions of Annona genus.

Plant Name/Standards	Plant Extract	MIC (µg/mL)
		ST	PA	KP	BC	EC	SA	PS	XC	AT	PM	PC	EH	TV	NB a	MD a	BC b	AN c	AI c	SM c	PI c	PG c
A. ambotay [80]	LF (EtOH)						9 b										10 b
A. cherimola [81]	SD (MeOH)												>100	15	5	8
A. cherimola [80]	LF (EtOH)						11b										14b
A. muricata [82,83,84]	LF (H2O)	4096	1024	512		>1024	>1024
A. muricata [81]	SD (MeOH)												>100	30	26	25
A. muricata [85]	SB (EtOH)		6.25	6.25	12.5
A. muricata [80]	STm (EtOH)
A. muricata [18]	RT (MeOH)		>32			>32	>32
A. squamosa [86]	SD (EtOH)							>771	>771	>771	>771	>771
A. squamosa [86]	SD (Acetone)							>475	>475	>475	>475	>475
A. squamosa [87]	SD (MeOH)		50 *			50 *	50 *
A. squamosa [78]	FR (MeOH)				1250 *	1250 *	1250 *
A. Senegalensis [88]	BK (MeOH)																	4.5	5.0	3.0	2.5	6.5
Streptomycin								10	10	20	10
Chloramfenicol							RST										30
Metronidazole													1.25	2.5
Ivermictine															0.8	1.3
Neomycin						312.5	312.5
Gentamycin			0.06	0.06	0.01		0.12

RST: Resistance; ^a LD₅₀ (µg/mL); ^b Inhibition zone (0.1 mg/disc, mm); ^c Inhibition zone (2 mg/disc, mm); LF:Leaf; SD: Seed; BK: Bark; STm: Stem; ST: Salmonella typhi; PA: Pseudomas aeruginosa; KP: Klebsiella pneumonia; EC: Escherichia coli 27; SA: Staphylococcus aureus 358; PS: Pseudomonas syringa e673; AT: Agrobacterium tumefaciens 431; XC: Xanthomonas campestris 2286; PC: Pectobacterium caratovorum 1428; PM: Pseudomonas marginalis 2758; AP: Aspergillus parasiticus 411; EH: Entamoeba histolytica; TV: Taenia vaginalis; NB: Nippostrongylus brasiliensis; Mollemades setae; BC: Bacilus subtilis; AN: Actinomyces naeslundii; AI: Actinomyces israelii; SM: Streptococcus mutans; PI: Privotella intermedia; PG: Porphyromonus gingivalis. * MIC was recorded in µg /mL.

Table 5.

Anti-microbial activities of alkaloids isolated from Annona genus.

Compound		MIC (µg/mL)
	KZ	SA	Sap	SE	Sep	EF	EC	PA	CA	CP	CD	CDb	Fm
A. salzmannii [89]													-
Liriodenine 11	-	>500	>500	50	50	-	-	-	-	-	50	100	-
Anonaine 8	50	>500	50	25	50	-	-	-	-	-	50	50	-
Asimilobine 9	50	>500	50	50	50	100	-	-	>500	>500	>500	50	-
Reticuline 19	250	>500	>500	100	100	250	-	-	100	100	>500	>500	-
Annona squamosal [90]
(−)-(R)-anonaine 8 [90]	-	-	-	-	-	-	-	-	-	-	-	-	30–39 *
Cleistopholine 1	-	-	-	250	250	250	-	-	-	-	-	250	-
Chloramphenicol	50	25	25	50	50	50	50	850	12.5	12.5	12.5	12.5	-

-: no data available; KZ: Kocuriarhizophila (ATCC 9341); SA: Staphylococcus aureus (ATCC14458); SAp:S. aureuspenicilinase-(8-); SE: Staphylococcus epidermidis (ATCC 12228); Sep; S. epidermidis (6ep); EF: Enterococcus faecalis (Ef); EC: Escherichia coli (ATCC 10538); PA: Pseudomonas aeruginosa (ATCC 27853)c; CA: Candida albicans (ATCC 10231); CA: Candida albicans(ATCC 10231); CP: Candida parapsilosis (ATCC 22019); CD: Candida dubliniensis (ATCC 777); CDb Candida dubliniensis (ATCC 778157); FM: Fusarium moniliforme. * inhibition diameter in mm.

Previous studies using alkaloid samples from sources other than Annona revealed, (−)-asimilobine 9 isolated from the bark of Beilschmiedia alloiophylla (Costa Rica) and B. kunstleri (Malaysia) indicated anti-fungal activity with an IC₅₀ value of 16.0 µg/mL [71]. (−)-Stepholidine 20 isolated from rattan stem of Fibraurea recisa had antifungal activity against drug resistant Candida albicans SM372, Candida krusei KM066, Candida parapsilosis SM304160, Cryptococcus neofarms SM9406204 with similar MIC value of 320 µg/mL [91]. Alkaloid (−)-roemerine 49 from the same stem indicated significant inhibition of C. albican transition from yeast to hyphae in a dose dependent manner [92]. Glaucine 68 isolated from the aerial component of Glaucium oxylobum showed moderate skin anti-fungal activities against Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes [93]. Antifungal activities of the non-Annona isolated alkaloids were evaluated against non-pathogenic fungi including liriodenine 11 from the wood of Michelia formosa which indicated a low activity against several wood decaying fungi both white and brown rot-fungi, Lenzites betulina, Trametes versicolor, Laetiporus sulphureus, Gloeophyllum trabeum, and Fomitopsis pinicola [94]. Similar alkaloids were also previously evaluated against pathogenic bacteria, including liriodenine from the roots of Zanthoxylum nitidum which showed a good antimicrobial activity against MRSA with MIC value of 93.8 µg/mL [95]. Liriodenine 11 from the stem of Mitrephira glabra Scheff was active against non-pathogenic bacteria, Micrococcus luteus, Mycobacterium sinegmatis, Saccharomyces cerevisae, and Aspergilus niger with an MIC value of 6.3, 12, 12, and 25 µg/mL, respectively [96].

5. Anticancer Alkaloids Present in the Genus Annona

In addition to the above antiprotozoal and antimicrobial activities, both the crude extracts from annona plants and the individual alkaloids have shown potent anticancer/antitumour activities.Many crude extracts of Annona species showed significant anti-cancer activities, but most of the bioactive constituents present in those crude extracts were acetogenins, fatty acids, and peptides [7]. However, wherever studied, it was known that some aporphine alkaloids, especially (−)-roemerine 49, which was isolated from the leaves of the wild custard apple, improved the response produced by vinblastine against multidrug-resistant KB-V1 or KB-3 cells (ED₅₀ > 20 µg/mL). This alkaloid appears to function by interacting with P-glycoprotein in the multidrug-resistant KB-V1 cell membrane vesicles [59]. The leaves of Annona muricata also showed potency to reduce gastric lesion, to expel parasitic worms and, moreover, the crude extract from the bark possessed anti-viral activity against herpes simplex virus type 1. The extracts and compounds also showed anticancer activities against breast cancer. Alkaloids, (−)-coclaurine 55, (+)-reticuline 19, argentinine 52, atherosperminine 54, and (+)-xylopine 65 were isolated from the root of Indonesian Annona muricata in which (−)-coclaurine 55, (+)-reticuline 19 were non-toxic against a human suspension cancer cell line (HL-60 leukemia cells) and two fibroblastic cell lines (A549 lung cancer cells and HepG2 liver cancer cells). (+)-Xylopine 65 exhibited the lowest IC₅₀ value ranging from approximately 20–80 µM [18].The alkaloid isocoreximine 39 isolated from Annona cherimola, at concentration of 50 µg/mL indicated cytotoxicity against K-562, U-251, PC-3, HCT-15, and MCF-7 with % inhibition of cell viability 94.15%, 65.23%, 78.71%, 63.05%, and 85.76%, respectively. Isocoreximine 39 showed in vitro cytotoxic activity against K-562, U-251, PC-3, HCT-15, and MCF-7 with % of inhibition of cell viability 94.15%, 65.23%, 78.71%, 63.05%, and 85.76%, respectively [34].

Although most of the alkaloids isolated from Annona species were reported with no anticancer activity data, there were cytotoxicity activity data on similar molecules obtained from non-Annona genus (Table 6). Interestingly, annomontine 54, a carbolated pyrimidine alkaloid was previously reported from the marine sponge Acanthostrongylophora ingens collected from Indonesian water. The alkaloid possessed pronounced anticancer activity against mouse lymphoma L5178Y compared to a standard control kahallide F [97]. The oxoaporphine alkaloid, liriodenine 11, was found in at least in twenty different species, ranging across flowering plants but mostly in annonaceae family. The alkaloid isolated from Brazilian Guatteria blepharophylla stem bark possessed anticancer activity against MCF-7 cell line with a more potent result compared to a standard drug doxorubicin with TGI value of 36.67 compared to 46.04 µM [98].

Table 6.

Anticancer/cytotoxicityactivities ofalkaloids that were obtained from non-Annona genera.

Alkaloid	Plants	Part of Plant	Country	Anticancer Activity	Ref(s)
(−)-Anonaine 8	Nelumbo nucifera Gaertn (Nelumbonaceae)	Leaves	Taiwan	Anti-proliferative effects with IC50 > 500 µM against AGS and 150.1 ± 0.3 µM against DU-145	[99]
	Michelia alba D.C. (Magnoliaceae)	Leaves	Taiwan	Inhibited viability of HeLa cancer cells (23 ± 1%) more effectively than non-cancer cells (Vero and MDCK cells, 75 ± 3% and 95 ± 4%, respectively) at concentration of 100 µM.	[100]
Annomontine 53	Acanthostrongylophora ingens (Petrosiidae)	Sponges	Indonesia	Pronounced cytotoxicity against L5178Y cell line with ED50 7.8 µg/mL compared to the positive control kahalalide F (ED50 6.3 μg/mL)	[97]
	Acanthostrongylophora ingens (Petrosiidae)	Sponges	Indonesia	Pronounced cytotoxicity against L5178Y cell line with EC50 0.49 µg/mL	[101]
Artabonatine B 23	Artabotrys hexapetalus (L.f.) Bhandari (Annonaceae)	Roots, stems, and leaves	Taiwan	Active against both Hep G2 and 2,2,15 cell lines with IC50 9.1 and 11.0 µg/mL, respectively	[102]
(−)-Asimilobine 9	Nelumbo nucifera Gaertn (Nelumbonaceae)	Leaves	Taiwan	Anti-proliferative effects against AGS and DU-145 cell lines with IC50 > 500 µM	[99]
Cleistopholine 1	Cananga odorata (Lam.) Hook.f. & Thomson (Annonaceae)	Fruits	Taiwan	Displayed potent cytotoxicity against Hep G2 (human hepatoma cell) and Hep 2,2,15 (Hep G2 cell line transfected with hepatitis B virus) cell lines with IC50 value of 0.22 µg/mL and 0.54 µg/mL, respectively	[103]
	Disepalum pulchrum (King) J.Sinclair (Enicosanthellum pulchrum, Annonaceae)	Roots	Malaysia	Active against CAOV-3 and SKOV-3 with IC50 value of 61.4 μM and 67.3 μM, respectively. This was comparable with that of the positive control cisplatin (62.8 μM and 67.1 μM) at 24 h of treatment. Cleistopholine (1) at >200 μM showed less cytotoxic effect against normal ovarian cells (SV40).	[104]
	Saprosma hainanense Merr. (Rubiaceae)	Stems	China	Inactive against against BEL-7402, SGC-7901, and K-562 cell lines	[105]
(−)-Corydine 29	Dicranostigma leptopodum (Maxim.) Fedde (Papaveraceae)	Whole plant	China	Showed its cytotoxicity against H1299, MCF-7, and SMCC-7721 with IC50 > 100 µM	[106]
	Stephania dinklagei (Engl.) Diels (Menispermaceae)	Aerial parts	Ghana	Exhibited cytotoxic activity against KB cell line with IC50 733 μM	[107]
(−)-Corydine 29	Stephania dinklagei (Engl.) Diels (Menispermaceae)	Stem	Ghana	(−)-Corydine 29 showed DNA-damaging activity in the yeast bioassay (IC50 values YCp50 gal, pRAD52 GAL, Prad52 GLU were27.5, >73.9, and 22.5 μg/mL, respectively	[108]
	Stephania kwangsiensis H.S. Lo. (Menispermaceae)	Root	India	Three different concentrations (20, 10, 5 µg/mL) could all significantly increase the apoptosis rate (8.77%, 9.12%, and 12.38%, respectively) of NCI-H446 cells after 48 h of treatment compared to the control group (1.02%). (−)-Corydine 29 can inhibit the proliferation of lung cancer NCI-H446 cells and induce their apoptosis	[109]
Corytuberine 16	Dicranostigma leptopodum (Maxim.) Fedde (Papaveraceae)	Whole plant	China	Cytotoxicity against H1299, MCF-7, and SMCC-7721 with IC50 value of 53.58 ± 5.47 µM, 72.30 ± 1.72 µM, and 73.22 ± 2.35 µM, respectively	[106]
Demethylsonodione 79	Hernandia nymphaefolia (Presi) Kubitzk (Hernandiaceae)	Trunk bark	Taiwan	Exhibited cytotoxic activity against P-388, KB16, A549 (human lung adenocarcinoma), and HT-29 (human colon carcinoma cell lines with ED50 value of 0.766, 0.507, 0.223, and 0.772 µg/mL	[110]
Dielsiquinone 3	Goniothalamus tamirensis Pierre ex Finet & Gagnep. (Annonaceae)	Stem bark	Thailand	Showed cytotoxic activity against A549, HT029, MCF7, RPMI and U251 with ED50 value of 0.11, 1.12, 0.11, 0.11 and 0.37 µM, respectively	[111]
Glaucine 68	Cassytha filiformis L. (Lauraceae)	Whole plant	Benin	Active compound against HeLa cell line with IC50 value of 8.2 µM	[112]
	Codiaeum variegatum (L.) Rumph. ex A.Juss. (Euphorbiaceae)	Leaves	Egypt	Showed cytotoxic activity against HepG2, MCF7, HCT116, and A549 cell lines with % of inhibition of cell viability of 38.4%, 46.3%, 66.8%, and 17.3%, respectively (at concentration of 100 µg/mL)	[113]
	Corydalis turtschaninovii Bess. (Papaveraceae)	Tuber	Korea	Showed cytotoxic activity against A549, SK-OV-3, SK-MEL-2 and HCT-15 cell lines with IC50 value of 26.76 ± 3.82, 21.57 ± 1.01, 20.39 ± 1.45 and 18.63 ± 4.15 µM, respectively	[114]
Isocoreximine 39	Guatteria blepharophylla Mart (Annonaceae)	Bark	Brazil	Showed anti-proliferative activity against UACC-62, MCF-7, NCI-H460, OVCAR-03, PC-3, HT-29, alagnd 786-0 with TGI value of >764.52 µM, and NCI-ADR/RES (TGI 131.50 µM). This compound showed selective activity for ovarian expressing phenotype for multiple drug resistance (NCI-ADR/RES) with a TGI value of 131.50 µM, but was less active than doxorubicin (TGI value of 14.80 µM)	[98]
(+)-Isocorydine 74	Cassytha filiformis L. (Lauraceae)	Whole plant	Benin	Inactive against HeLa cell with IC50 > 80 µM	[112]
	Papaver rhoeas L. Papaver rhopalothece Stapf, Papaver macrostomum Boiss. & A.Huet (Papaveraceae)	Aerial parts	Turkey	Nontoxic against normal Vero cell with IC50 value of >300 μg/mL	[115]
Lanuginosine 10	Magnolia grandiflora L. (Magnoliaceae)	Leaves	Egypt	Exhibited cytotoxicity against U251 and HEPG2 with IC50 value of 4 μg/mL and 2.5 μg/mL, respectively. Lanuginosine 10 was found to be inactive against the HeLa cancer cell.	[116]
Liriodenine 11	Anomianthus dulcis (Dunal) J. Sinclair (Annonaceae)	Stem bark	Thailand	Exhibit the growth of NCIH187, BC, and KB cell lines with IC50 values at 1.02, 13.45 and 14.57 µg/mL, respectively	[117]
	Broussonetia papyrifera (L.) L′Hér. ex Vent. (Moraceae)	Fruits	China	Exhibit strong cytotoxic effect against A375, BEL-7402, and HeLa cell lines with IC50 value of 5.38 ± 0.27, 6.61 ± 0.57, and 5.97 ± 0.39 µg/mL, respectively	[118]
	Cananga odorata (Lam.) Hook.f. & Thomson (Annonaceae)	Stem bark	Bangladesh	Show cytotoxic activity based on brine shrimp method with LC50 value of 4.89 μg/mL	[119]
	Cyathostemma argenteum Wild & R.B.Drumm (Vitaceae)	Roots	Malaysia	Found to be similarly and moderately cytotoxic against MCF-7 ADR MDA-MB435 and MT-1 cells lines with IC50 values of 15.6, 16.7, 6.4 and 18.2 µM, respectively	[120]
	Disepalum plagioneurum (Diels) D.M.Johnson (Syn Polyalthia plagioneura Diels, Annonaceae)	Stem	China	Cytotoxic activity against GSC-7901, K562, and SPCA-1 cell lines with IC50 value of of 3.87, 37.61, and 6.19 µM, respectively	[121]
	Disepalum pulchrum (King) J.Sinclair (syn Enicosanthellum pulchrum (King) Heusden, Annonaceae)	Root	Malaysia	Inhibited CAOV-3 cell growth with IC50 value of.3 ± 1.06 µM after 24 h of exposure. Exhibited less activity against SKOV-3 cells, with IC50 values of 68.0 ± 1.56 µM.	[122]
	Goniothalamus gitingensis Elmer (Annonaceae)	Leaves	Philippines	Effective antiproliferative effects against HUVEC and K-562 cell lines with GI50 value of 8.2 ± 0.3 and 6.1 ± 0.8, respectively.	[123]
Liriodenine 11	Guatteria aberrans Erkens & Maas (Syn Guatteria f riesiana (W.A. Rodrigues) Erkens & Maas, Annonaceae)	Stem bark	Brazil	Anticancer potent against B16-F10 (mouse melanoma), HepG2 (human hepatocellular carcinoma), HL-60 (human promyelocytic leukemia), and K562 (human chronic myelocytic leukemia) tumor cell lines with IC50 values of >10, 8.3, 5.5, and 5.0 μM for the respectively	[124]
	Guatteria blepharophylla Mart. (Annonaceae)	Bark	Brazil	Showed anti-proliferative activity against UACC-62, MCF-7, NCI-H460, OVCAR-03, PC-3, HT-29, 786-0 and NCI-ADR/RES with TGI value of 63.02, 37.67, 87.41, 372.18, >909.09, >909.09, >909.09 and >909.09 µM, respectively. This compound undermined positive control doxorubicin against MCF-7 with TGI value of 46.04 µM.	[98]
	Magnolia duperreana Pierre (Syn Kmeria duperreana (Pierre) Dandy, Magnoliaceae)	Stem bark	Thailand	Found to be active against KB and P388 cell lines with ED50 value of of 1.7 and 0.8 µg/mL, respectively	[125]
	Magnolia floribunda (Finet & Gagnep.) Figlar (Syn Michelia floribunda Finet & Gagnep., Magnoliaceae)	Stem bark	Thailand	Indicated cytotoxic activity against KB and P388 cell lines with with ED50 value of <2.5 µg/mL	[126]
	Michelia compressa var. formosana (Magnoliaceae)	Heartwood	Taiwan	Exhibited powerful inhibitory activity against TW01, H226, Jurkat, A498, A549, and HT1080 carcinoma cell lines with IC50 value of were 8.99, 14.71, 15.7, 4.52, 8.82 and 9.75 μM, respectively	[127]
	Michelia compressa var. lanyuensis (Magnoliaceae)	Roots	Taiwan	Possessed cytotoxicity against B16F10 cells after 24 h treatment at high concentration (100 μM) with 80% of cell viability.	[128]
	Microcos paniculata L. (Malvaceae)	Branche	Vitenam	Showed low activity against HT-29 cancer cell line with IC50 values greater than 10 μM.	[129]
	Miliusa sinensis Finet & Gagnep. (Annonaceae)	Leaves and branches	Vietnam	Indicated a good activity against MCF-7, KB, LU and Hep-G2 cancer cell lines with IC50 value of 2.89, 2.30, 6.66 and 5.23 μg/mL, respectively	[130]
	Nelumbo nucifera Gaertn (Nelumbonaceae)	Leaves	Taiwan	Showed anti-proliferative effects against AGS and DU-145 cell lines with IC50 value of >500 and 95.4 ± 0.4 µM, respectively	[99]
	Polyalthia longifolia var. pendula (Annonaceae)	Bark	Taiwan	Showed activity against MCF-7 (breast cancer) and MDA-MB-231 cell line with IC50 value of 4.46 and 10.28 µg/mL, respectively	[131]
Liriodenine 11	Pseuduvaria setosa (King) J. Sinclair (Annonaceae)	Aerial part	Thailand	Strongly cytotoxic to KB and BC cell lines with IC50 2.4 µg/mL and 2.3 µg/mL, respectively	[132]
	Saprosma hainanense Merr. (Rubiaceae)	Stems	China	Exhibit cytotoxic activities against BEL-7402, SGC-7901, and K-562 cell lines with IC50 value of 71.7, 33.7, and 197.7 µM, respectively	[105]
	Stephania dinklagei (Engl.) Diels (Menispermaceae)	Aerial parts	Ghana	Exhibit cytotoxic activity against KB cell line with IC50 value of 26.9 ± 2.4 μM	[107]
	Stephania dinklagei (Engl.) Diels (Menispermaceae)	Stem	Ghana	Showed DNA-damaging activity in the yeast bioassay against YCp50 gal, pRAD52 GAL, Prad52 GLU with IC50 value of 0.6, 1.5, and 0.5 μg/mL, respectively.	[108]
	Unonopsis guatterioides (A.DC.) R.E.Fr.(Sin Unonopsis buchtienii R. E.Fries, Annonaceae)	Stem	Bolivia	Possessed cytotoxic bioactivity against Vero cell line with IC50 value of 1 μg/mL	[133]
	Zanthoxylum nitidum (Roxb.) DC. (Rutaceae)	Stem bark	China	Exhibit cytotoxicity against three human cancer cell lines HT29, A549 and MDA-MB-231 with IC50 values of 9.12, 6.05, and 11.35 μM, respectively	[134]
	Zanthoxylum nitidum (Roxb.) DC. (Rutaceae)	Stem bark	Taiwan	Exhibit moderate cytotoxicity against MCF-7, NCI-H460, and SF-268 cancer cell lines with IC50 values of 3.19, 2.38, and 2.19, respectively. Liriodenine (11) was the most cytotoxic isolate in Zanthoxylum nitidum	[135]
(+)-Nornuciferine 73	Guatteria blepharophylla Mart (Annonaceae)	Stem bark	Brazil	Anti-proliferative activity against MCF-7 NCI-H460 PC-3 HT-29786-0 K562 and NCI-ADR/RES with TGI value of 215.58, 201.99, 542.38, 191.38, 615.23, 153.88 and 255.37 µM, respectively.	[98]
	Nelumbo nucifera Gaertn (Nelumbonaceae)	Leaves	Taiwan	Anti-proliferative effects against AGS and DU-145 cell lines with IC50 value of >500 µM	[99]
	Phoebe grandis (Nees) Merr. (Lauraceae)	Leaves	Malaysia	Cytotoxic activity against NIH/3T3, HeLa and HL-60 with CD50 value of 17, 15 and 37 µg/mL, respectively.	[136]
(+)-Reticuline 19	Argemone Mexicana L. (Papaveraceae)	Whole plant	Taiwan	Cytotoxic effects against HONE-1 (96% of control) and NUGC (90% of control) at concentration of 150 µM	[137]
	Dehaasia longipedicellata (Ridl.) Kosterm. (Lauraceae)	Stem bark	Malaysia	Cytotoxicity activities against A549 (IC50 > 200 µg/mL), A375 (IC50 97.600 µg/mL), and BxPC-3 (IC50 82.570 µg/mL)	[138]
	Hernandia nymphaefolia (Presi) Kubitzk (Hernandiaceae)	Trunk bark	Taiwan	Anticancer activity against P-388, KB16, A549 (human lung adenocarcinoma), and HT-29 (human colon carcinoma cell lines with ED50 > 50 µg/mL	[139]
Roemerine 49	Nelumbo nucifera Gaertn (Nelumbonaceae)	Leaves	Taiwan	Showed anti-proliferative effects against AGS and DU-145with IC50 value of >500 and 95.4 ± 0.4 µM, respectively	[99]
(−)-Stepholidine 20	Polyalthia longifolia (Sonn.) Thwaites (Annonaceae)	Bark	Taiwan	Activity against MCF-7 (breast cancer) cell line with IC50 value of 16.56 µg/mL	[131]
Squamolone 82	Artabotrys hexapetalus (L.f.) Bhandari (Syn Artabotrys uncinatus (Lam) Merr., Annonaceae)	Roots, stems, and leaves	Taiwan	Showed significant activity against Hep G2 and 2,2,15 cell lines with IC50 value of 2.8 and 1.6 µg/mL, respectively	[102]

6. Conclusions

This review presents the ethnomedicinal, alkaloidal and biological, properties of Annona species with respect to reported anti-infective and anti-cancer activities. The Anonna species: A. muricata (soursop), A. squamosa (custard apple), A. senegalensis (wild custard apple), and A. cherimola (cherimola) are renowned traditionally for their anti-tumor properties. Among these, A. muricata is widely studied and has shown broad range of biological activities including anti-protozoal, anti-cancer, anti-tumour, antimicrobial, and antiparasitic properties. This species has also produced several patents and commercial products. Investigations into extracts from the leaves, bark, fruit, and seeds of this plant genus have found terpenoids, steroids, flavonoids, cardiac glycosides, tannins, phenols, sugars, fatty acids, acetogenins, and alkaloids. As many as 200 phytochemicals belonging to these chemotypes have been identified and isolated from this Annona muricata species alone, with the most important being acetogenins, phenols and anonaine alkaloids. Anonaine and its structurally related alkaloids were the most abundant and commonly available alkaloids in Annonaceae family. The oxoaporphine alkaloid, liriodenine, was found in at least in twenty different species, ranging across flowering plants but mostly in annonaceae family. The alkaloids from Annona species have rarely been explored for their medicinal applications. However, wherever studied, Annona alkaloids have been reported to possess anti-inflammatory, anti-cancer, antitumor, anti-HIV, antiprotozoal, antiparasitic, antidiabetic, analgesics, gastroprotective, antihypertensive, hepatoprotective, nephroprotective, and neuroprotective properties. Amongst these broad-ranging properties, anti-cancer and anti-tumour activities of both the crude extracts and alkaloids is commendable. Most interesting and noteworthy of this Annona genera is that the pharmacological properties accentuate the ethnomedicinal utilization of this plant, as well as its usefulness in the agrifood sector. Liriodenine, annonaine, glaucine and cleistopholine showed potent anti-cancer, anti-tumour, and cytotoxicity activities against many human cancer cell lines, and it is worthwhile to pursue detailed clinical investigations of these alkaloids. To the best of our knowledge, there is no clinical study that was successfully completed on the extracts rich in acetogenins or alkaloids. In this respect, it is also necessary to conduct scientific studies to establish optimal and safe doses of consumption of both the plant extracts and their phytochemicals especially alkaloids. This is because the use of the Annona plants is popular not only in Indonesia, but wide across the tropical countries.

Author Contributions

Conceptualization, A.S.N., P.W., P.A.K.; data curation and analysis 1960–2015, A.S.N.; data curation and analysis 2015–2019, A.S.N., Y.D.D.; making and editing of the figures, A.S.N., Y.D.D.; writing—original draft preparation, A.S.N., Y.D.D., P.W., P.A.K.; writing—review and editing, A.S.N., Y.D.D., P.W., P.A.K.

Funding

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest.