A recent review on phytochemical constituents and medicinal properties of kesum (Polygonum minus Huds.)

Abstract

Medicinal plants and herbal preparations are gaining renowned interest in scientific communities nowadays due to their reliable pharmacological actions and affordability to common people which makes them effective in control of various diseases. Polygonum minus (Polygonaceae) locally known as kesum is an aromatic plant commonly used in Malay delicacies. The plant is having potential applications due to its high volatile oil constituents in perfumes and powerful antioxidant activity. It has been used traditionally to treat various ailments including dandruff. The research has been carried out by various researchers using different in vitro and in vivo models for biological evaluations to support these claims. This review paper may help upcoming research activities on Polygonum minus by giving up to date information on the phytochemical constituents and medicinal properties of kesum to a possible extent with relevant data.

1. Introduction

Polygonum minus (P. minus) is commonly known as pigmy knot weed in English and kesum in Malay[1] which belongs to the family Polygonaceae. This plant has sweet and nice aroma hence commonly used as flavoring ingredient in preparation of ulam (salad), laksa and several other Malay food delicacies. The plant is found in Southeast Asian countries namely Malaysia, Indonesia, Thailand (Phak pai) and Vietnam. The plant produces essential oil containing high levels of aliphatic aldehydes (72.54%)[2]; and it has been recognized by the Malaysian government as an essential oil-producing crop in the Herbal Product Blueprint[3]. The plant is found growing wild especially in damp areas such as the side ditches or nearby rivers and lakes. P. minus is a slender, creeping shrub and can reach up to a height of 1.0 m in lowland and up to 1.5 m in the highlands. The leaves are narrow and lanceolate, 5-7 cm long and 0.5-2.0 cm wide (Figure 1), dark green in color and very aromatic and arranged in alternate manner on the stem. The stem is cylindrical, dark green with a little reddish color with short internodes and nodal segments of simple roots[4]. Inflorosence is apical, flowers are small white purple-colored 1.5 to 2.0 mm long and lenticular black or dark brown coloured fruits.

Figure 1. Image of P. minus along with inflorescence enlarged.

Traditionally P. minus has been used in herbal medicine as a cure for digestive disorders and dandruff in Malaysia despite of its regular uses as food flavoring agent and appetizer in Malays cuisine. The essential oil extracted from P. minus leaves is applied to hair to remove dandruff, used in aroma therapy[5] and in the perfume industry[4]. P. minus has also been reported to possess several pharmacological properties like antimicrobial activity[6], cytotoxic activity against HeLa (human cervical carcinoma)[7], antioxidant activity[8] and anticancer activity[9],[10]. The aim of this paper is to review the recent reports on phytochemical constituents and medicinal properties of P. minus which may help future researchers working with this plant.

2. Phytochemical constituents

Plant-produced chemical compounds or phytochemicals like alkaloids, glycosides, flavonoids, volatile oils, tannins, resins have been used in a wide range of commercial and industrial applications such as flavors, aromas and fragrances, enzymes, preservatives, cosmetics, bio based fuels and plastics, natural pigments and bioactive compounds. The research on phytochemicals and use of phytochemicals is increasing more because of the harmful side effects of the synthetic compounds. Various reports have been published regarding the phytochemical content of P. minus and reported to have different phytochemical compounds. Urones et al.[11] isolated two new components from the ether extract of P. minus a flavone: 6,7-methylenedioxy-5,3″,4″,5″ tetramethoxyflavone and a methyl flavonol: 6,7-4″,5″dimethylenedioxy-3,5,3″-trimethoxyflavone. Yaacob[12] have reported that the flavor of P. minus is due to the presence of decanal (24.36%) and dodecanal (48.18%) mainly, along with them he had isolated 1-decanol, 1-dodecanol, undecanal, tetradecanal, 1-undecanol, nonanal, 1-nonanol and β-caryophyllene. Qader et al.[13] showed the presence of phenolic compounds like gallic acid, rutin, coumaric acid and quercetin in leaves. Baharum et al.[14] have analysed the essential oil of P. minus using Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry (GC-TOF MS) and identified 48 compounds (Table 1).

Table 1. Phytochemical constituents of P. minus reported from plant and in vitro cell cultures.

Name of plant material	Name of phytochemical constituents
Leaves	Gallic acid, rutin, coumaric acid, quercetin
Roots	Nonane (1.65), heptane (1.11), octadecanal (3.08), β-caryophyllene (17.57), trans-α-bergamotene (2.13), β-farnesene (2.84), α-caryophyllene (9.50), p-benzoquinone (1.85), phenol (2.73), α-panasinsen (1.82), pentanoic acid (1.47), octane (1.42), heptane (0.44), undecane (0.52), 1,2 benzenedicarboxylic acid (0.52), nonane (0.44)
Callus	2-furanmethanol (0.35), 2 (5H)-furanone (1.75), 2-hydroxy-2-cyclopenten-1-one (6.67), 2,4-dihydroxy-2,5-dimethyl-3(2H)-furan-3-one (0.20), 2H-pyran-2,6 (3H)-dione (0.26), 2-hydroxy-gamma-butyrolactone (3.08), 2,5-dimethyl-4-hydroxy-3 (2H)-furanone (1.93), 2,5-furandicarboxaldehyde (0.98), 2,3-dihydro-3,5-dihydroxy-6-methyl 4H-pyran-4-one (1.66), (S)-(+)-2′,3′-dideoxyribonolactone (0.882), 5-(hydroxymethyl)-furancarboxaldehyde (18.51), 3-deoxy-D-mannoic lactone (19.44)
Essential oil	2-hexenal (0.001), cis-3-hexenal (0.022), decanal (23.121), 1-decanol (2.090), 1-dodecanol (1.380), undecanal (0.990), dodecanal (38.635), 1-dodecanal (4.785), tetradecanal (1.506), hexadecanal (0.004), cyclodecanol (5.691), undecane (2.286), nonane (0.062), nonanal (0.010), 3-carene (1.202), camphene (0.009), sabinene (0.013), 2-butyltetrahydrofuran (0.004), 1-cyclopropylpentane (0.005), isobornyl formate (0.071), α-copaene (0.024), octylcyclopropane (0.001), (z,e)-α-farnesene (0.928), α-cedrene (0.012), (e)-β-caryophyllene (0.212), α-bergamotene (0.801), γ-gurjunene (0.095), α-humulene (2.293), trans-β-farnesene (0.907),2-isopropenyl-4a,8-dimethyl-1,2,3,4,4a,5,6,7-octahydronaphthalene (0.697), α-curcumene (0.080), valencene (0.806), alloaromadendrene (0.039), β-bisabolene (0.014), α-zingiberene (0.013), α-panasinsene (0.563), δ-cadinene (0.025), patchulane (0.004), nerolidol (0.075), caryophyllene oxide (1.513), ocimene (0.055), dehydro-cyclolongifolene oxide (0.544), acoradiene (0.079), 1,3,6,10-dodecatetraene (0.117), 4,4 dimethyltetracyclo [6.3.2.0(2,5). (1,8)] tridecan-9-ol (0.122), drimenol (0.574), phytol (0.003)

*with in brackets is peak percentage of the compound.

Ismail et al.[15] studied the presence of phytochemical constituents in P. minus root cultures and reported 16 compounds (Table 1). Shukor et al.[16] identified 12 chemical compounds in leaf cell cultures which were not present in P. minus intact plants (Table 1). Several new compounds like 2,2′-bioxirane; propanoic acid-2oxo-methyl ester; repandin A; 2-propanone, 1,3-dihydroxy-imidazolidine- 2,4,5-trione; and 2-acetyl-2-hydroxy-butyrolactone were found in elicitated cell cultures but not found in the control culture.

3. Medicinal properties

Various studies have revealed the different pharmacological potentials of P. minus both in vitro and in vivo test models. P. minus have demonstrated to possess cytoprotective, antibacterial, antifungal, antiulcer, antiviral and antioxidant activities. These properties have been described in greater detail in the following subsections.

3.1. Antibacterial activity

Resistance of many bacteria against antibiotics is alarmingly increasing and the side effects associated with the usage of antibiotics are also a major problem in treatment of infectious diseases. Therefore, search for new substances with antimicrobial activity has become an urgent necessity. Medicinal plants have been used in development of drugs from long time and compounds with antimicrobial activity from plant origin are the possible alternative to the problems faced by usage of synthetic antimicrobial compounds. Most of the research in this area is going on development of newer antimicrobials with more potent activity either from the plant derived compounds or from their synthetic analogues. Musa et al.[17] showed that P. minus aqueous extract had no significant activity against 10 isolated pathogenic fish bacteria namely Aeromonas hydrophila, Citrobacter freundii, Edwardsiella tarda, Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Streptococcus agalatiae, Streptococcus aginosus, Vibrio alginolyticus, Vibrio parahaemolyticus and Vibrio vulfinificus. Jamal et al.[18] also reported that the distilled water extract of P. minus did not show any activity on Bacillus subtilis (B. subtilis) and E. coli however ethanolic and methanolic extracts showed activity against B. subtilis and no activity on E. coli. On the contrary Haasim et al.[19] reported that P. minus water extract showed activity on E. coli but did not show any activity on B. subtilis and S. aureus while ethanol and methanol extracts showed good activity on B. subtilis, S. aureus and E. coli. Further, Nurul et al.[20] demonstrated that the aqueous extracts of P. minus were slightly more effective in preventing microbial growth on refrigerated duck meatballs.

3.2. Antifungal activity

Johnny et al.[21] carried out a study on antifungal activity of 15 plants incliuding P. minus using Colletotrichum capsici isolated from chillies as test organism and reported that methanolic extract shown activity against Colletotrichum capsici. Ong et al.[22] reported that when P. minus was made into a paste and mixed with kerosene and applied on the skin to get rid of the fungal infections.

3.3. Antiviral activity

Plants have had a long evolution of resistance against viral agents and laid alternative ways in drug development to treat viruses. Extensive studies have shown that medicinal plants contain compounds active against viruses that cause human diseases. Therefore, plant extracts and phytochemicals are getting more importance as potential source for viral inhibitors. Ali et al.[9] reported the antiviral properties of P. minus against herpes simplex variety 1 and vesicular stomatitis virus. The ethanolic extract of P. minus had shown strong antiviral against herpes simplex variety 1 and weak activity against vesicular stomatitis virus.

Table 2. Medicial properties of P. minus.

Medicinal property	Extracts used	References
Antibacterial activity	Ethanol, Methanol	[17]
	Ethanol, Methanol, Distilled water	[18]
	Distilled water	[19]
Antifungal activity	Methanol	[20]
	Mixed with kerosene	[21]
Antioxidant activity	Plant juice	[23]
	Distilled water	[22]
	Distilled water	[19]
	Methanol	[8]
	Ethanol, Distilled water	[24]
	Ethanol, Methanol, Distilled water, Methanol 50%, Methanol 70%, Ethanol 50%, Ethanol 70%	[18]
Antiulcer activity	Distilled water	[26]
	hexane:ethyl acetate 1:1 v/v, ethyl acetate:methanol 1:1 v/v, methanol:acetonitrile 1:1 v/v, acetonitrile:distilled water 1:1 v/v, Distilled water	[27]
	Petroleum ether, methanol and chloroform	[9]
Avtiviral activity	Ethanol	[10]
Acute Toxicity	Distilled water	[28]
Cytotoxicty	Petroleum ether, methanol and chloroform	[9]
Cytoprotectivity	Distilled water	[26]

3.4. Antioxidant activity

It is now well known that the generation of free radicals or reactive oxygen species from incomplete reduction of molecular oxygen during aerobic respiration is closely related to cellular damage. Regulation of the balance between the production of reactive oxygen species by cellular processes and its removal by antioxidant defense system maintains normal physiological processes. Antioxidant compounds in food play an important role as a health protecting factor in diseases like cancer, coronary heart diseases and they are also used as natural food preservatives. P. minus is considered as a potential source of natural antioxidants due to high content of gallic acid, total phenolic content and reducing power[5],[23]. Maizura et al.[24] extracted P. minus by using juice extractor without adding any additional solvent and reported to have high antioxidant property. Aqueous extract of P. minus has shown good antioxidant properties and there was no significant difference with synthetic antioxidant (butyl hydroxyl toluene) (BHT)[23]. Nurul et al.[20] reported that P. minus aqueous extract showed potential antioxidant effects on duck meatballs and gave better results when compared to synthetic antioxidant BHT. Methanolic extract of P. minus showed no significant difference with butyl hydroxyl anisole and was superior to BHT in reducing Fe (III) to Fe (II)[25]. In another report P. minus ethanol extract showed higher antioxidant activity when compared to aqueous extract and there is no significant difference with synthetic antioxidant gallic acid[26]. P. minus is extracted with water, ethanol and methanol in different concentrations and 70% methanol showed more activity than rest of extracts and the yield of extract is also more for 70% methanol[19]. All these results clearly indicate that difference in solvents used for preparing the extract affect the antioxidant activity[27].

3.5. Antiulcer activity

Peptic ulcer is one of the common diseases affecting nearly 10% of world population and the treatment for this disease have to be improved more than the existing therapies because of the side effects. For common problems like gastric ulcers it is better to use plant derived preparations as they can be easily available and most of the plants are even consumed in daily diet. The efficiency of some extracts in liquid medium and at low pH levels enhances their potency even in the human stomach make them more reliable. Oral administration of P. minus aqueous extract at dose of 250 and 500 mg/kg body weight both in normal and rats with ethanol induced ulcers showed significant inhibition of ulcerous areas in a concentration dependent manner and there was no significant difference with omeprazole used as reference[28]. Qader et al.[13] reported that ethyl acetate: methanol 1:1 fraction of P. minus was shown to have gastroprotective activity against oxidative stress caused by ethanol induction and all the fractions of ethanol extract significantly significantly reduced the area of ulceration when compared with the carboxy methyl cellulose. The presence of phenolic compounds like gallic acid and coumaric acid is responsible for gastroprotective activity[29]. In vitro anti Helicobacterium pylori tests of P. minus were carried out along with 32 selected medicinal plants used in Malaysian traditional medicine for gastrointestinal disorders and wounds. High zone of inhibition was observed against H. pylori using P. minus petroleum ether (15.5 mm), methanol (15.5 mm) and chloroform (12.3 mm) extracts whereas no inhibition zone was speculated in aqueous extract[6].

3.6. Acute toxicity and cytoprotectivity

Studies on acute toxicity of a plant drug are essential to assess the toxic effects of plant preparations on human health. Acute toxicity studies of compounds are generally carried out in animals or in vitro models. Acute toxicity of P. minus was assessed and no mortality was observed in rats fed with P. minus extracts. Histological observation of the liver and kidneys for any changes or modifications indicated no alteration to the treated organs and serum biochemistry revealed that there was no significant difference between the test and control groups. It is concluded that the extract was quite safe even at higher doses and had no acute toxicity[28]. Wasman et al.[28] reported that the aqueous extract of P. minus has cytoprotective properties.

3.7. Cytotoxicity and genotoxicity

Cytotoxic studies are carried out to reveal the toxic effect of plant extracts or drugs when consumed by humans and cytotoxic activities can also used for assessing anticancer activity of the extracts. Ali et al.[9] reported that P. minus demonstrated cytotoxicity (50% cytotoxic dose or CD₅₀: 0.1 mg/mL) against HeLa cells while P. minus has been assessed against normal lung fibroblast cell line Hs888Lu and the results did not present any inhibition percentage of cell viability in both ethanol and aqueous extracts[26]. Genotoxic studies are used to determine the doses of plant extracts or drugs that either damage DNA or alter basic cellular pathways important for maintaining genomic integrity. Wan-Ibrahim et al.[30] has proved that aqueous extract of P. minus has no genotoxic effect on human lymphocytes.

4. Conclusion

In the present paper, we have reviewed the relevant literature to congregate the phytochemicals, secondary metabolites and pharmacological information on P. minus. The presence of decanal, dodecanal and many other aldehydes make P. minus a major source of perfume. The phenolic compounds like gallic acid and coumaric acid are responsible for many activities including antioxidant and antiulcer activity. Antioxidant studies revealed the potential of P. minus as a food preservative and antioxidant. Compounds isolated from P. minus callus cell culture such as 5-hydroxymethyl-furancarboxaldehyde or hydroxymethylfurfural or HMF have inhibition of sickle cell blood production property and repandin A has antidiabetic activity. But these valuable compounds are absent in intact plants which makes cell suspension culture of P. minus a valuable tool for production of these compounds. The toxicity studies on P. minus concluded that the extracts were quite safe even at higher doses and had no toxic effects on cell lines used.

Comments

Background

P. minus is commonly used in Malaysia as food and medicine. The plant has potential applications in preparation of perfumes, production of volatile oils and potent antioxidant properties. Secondary metabolites produced from the plant are diverse in nature and important both medicinally and industrially. There is a need for detailed description of the plants phytochemical constituents and pharmacological properties to increase awareness and usage of the plant in diverse fields.

Research frontiers

Data from three dimensions of the plant viz. phytochemical analysis of intact plant, secondary metabolite analysis from cell cultures and pharmacological studies of the plant.

Related reports

Suhailah Wasman Qader et al. published an article about Potential bioactive property of P. minus Huds (kesum) review.

Innovations and breakthroughs

Data regarding phytochemicals from cell suspension cultures of P. minus are presented here along with phytochemicals from intact plants along with their chemical structures which will give simple yet informative ideas about the plant.

Applications

The key application of this review is providing information about phytochemical and pharmacological properties of the plant which improves the usage of plant for health benefits and stands as a guide for future research on the plant.

Peer review

This review acts as a valuable note of information regarding the chemical composition and pharmacological uses of P. minus. It is providing simple yet efficient data on the topics it covered which is useful for laying ways to newer and intensive researches on P. minus.