A review of the literature and latest advances in research of Piper sarmentosum

Abstract

Context: Piper sarmentosum Roxb. (Piperaceae) is a traditional medicinal as well as a culinary plant in South East Asian countries, whereby aerial parts of the plant are consumed as a vegetable in various forms and the whole plant or parts are used as folk remedies, alone or in combination with other herbs, to treat various ailments. The plant has extensively been investigated in a broad range of studies to provide scientific evidence for folklore claims or to find new therapeutic uses; however, heretofore, a summary of the data are not available.

Objective: In order to describe nutritional and therapeutic potential of P. sarmentosum and summarize scientific evidence that supports traditional claims, a literature review and latest advances in research of the plant are given herein.

Materials and methods: The literature has been retrieved from a number of databases such as Google Scholar, PubMed, Medline, Science Direct and SciFinder. The articles related to synthetic work, ecology and agriculture have been excluded.

Results and discussion: The review has not only revealed a number of pharmacological activities supporting the traditional claims but indicates new prospects for the plant. Antiangiogenic activity and toxicity studies suggest the usage of the plant in treating diseases involving neo-vascularization. The available efficacy, safety, pharmacokinetic and stability data urge clinical studies on extracts of the plant.

Conclusion: The present review may be helpful to future researchers intending to investigate the plant and natural pharmaceutical industry for preparing evidence-based formulations.

Keywords::

• Piperaceae
• phytochemical
• pharmacological
• analytical
• stability

Botany

Scientific name: Piper sarmentosum Roxburgh (Piper is a Latin name of Pepper and sarmentosum means twiggy with long slender runners).

Vernacular names: Kadok, Daun Kadok, Chau pulu, Jia ju.

Synonyms: Chavica hainana DC., Chavica sarmentosa (Roxburgh) Miq., Piper alispicum DC., Piper brevicaule DC., Piper gymnostachyum DC., Piper lolot DC., Piper pierrei DC., Piper saigonese DC.

Family: Piperaceae.

Habitat: The plant is widely found in Cambodia, Laos, Philippines, Burma, Thailand, Malaysia, Indonesia, Vietnam and China. The plant is reported to be growing in Andaman Islands (Mathew et al., 2004).

Botanical description: The plant is herbaceous shrub, creeping along the ground or erect, growing up to 50–60 cm, usually found as a weed in villages at shady places (Hsuan, 1990). Petiole 1.0–2.5 cm long, leaf blade thin to thick papery, light to dark green, broadly ovate to elliptic, 4.5–6.0 cm wide, 7.5–9.5 cm long, apex acute, leaves on epiphytic base deeply equally cordate with rounded lobes, leaves on free branch base cuneate to subtruncate, veins 7, all basal. Spike with male and female flowers together straight, cylindrical, 1.5 cm long, 0.3–0.5 cm in diameter, peduncle ca. 1.5 cm long, bract rounded, stamen 1, stigmas 3–4. Female spike white cylindric, other characters are as above. Fruiting spike 1–2 cm long and 0.5–1.0 cm in diameter; flowering is round the year, plenty in rainy season (Wiart, 2006). The plant has a characteristic pungent odor (Wee, 1992; Chaveerach et al., 2008). The picture of the plant is shown in Figure 1.

Figure 1.  Pictures of Piper sarmentosum Roxb.

Ethnopharmacology

In Chinese traditional medicine system, leaves of the plant are used to treat fever and indigestion (Chaveerach et al., 2008), roots are used to relieve toothache and treat dermatomycoses, coughing and pleurisy (Perry, 1981; Duke & Ayensu, 1985; Toong & Wong, 1989; Chaveerach et al., 2008) and fruit is used as an expectorant (Pongboonrod, 1976; Toong & Wong, 1989). In Malaysia and southern parts of Thailand, leaves are used externally to sooth headache. Moreover, in Negeri Sembilan, a state of Malaysia, crushed leaves are used to treat kidney stones (Ong & Norzalina, 1999). In Indonesia, roots are chewed for cough, asthma and toothache, and leaves are used to mitigate chest pain (Wiart, 2006).

Edible uses

Aerial parts of the plant are consumed after cooking or boiling in water as a functional food. And the cooked food is termed as Ulam in Malaysia and Indonesia. Certain traditional cuisines are wrapped in leaves of the plant to impart aroma and enhance taste.

Chemical constituents

The chemical constituents identified in the plant are pellitorine (Likhitwitayawuid & Ruangrungsi, 1987; Thitima et al., 2004; Tuntiwachwuttikul et al., 2006; Hussain et al., 2010a), guineensine (Thitima et al., 2004; Tuntiwachwuttikul et al., 2006), brachystamide B (Thitima et al., 2004; Tuntiwachwuttikul et al., 2006), sarmentine (Likhitwitayawuid & Ruangrungsi, 1987; Thitima et al., 2004; Tuntiwachwuttikul et al., 2006; Hussain et al., 2010a), brachyamide B (Thitima et al., 2004), 1-piperettyl pyrrolidine (Thitima et al., 2004), 3,4,5-trimethoxycinnamoyl pyrrolidine (Thitima et al., 2004), sarmentosine (Likhitwitayawuid & Ruangrungsi, 1987; Thitima et al., 2004; Tuntiwachwuttikul et al., 2006; Hussain et al., 2010a), (+) asarinin (Thitima et al., 2004), sesamin (Thitima et al., 2004; Tuntiwachwuttikul et al., 2006), N-[9-(3,4-methylenedioxyphenyl)-2E,4E,8E-nonatrienoyl] pyrrolidine (Tuntiwachwuttikul et al., 2006), methyl piperate (Thitima et al., 2004), β-sitosterol (Likhitwitayawuid & Ruangrungsi, 1987; Thitima et al., 2004; Tuntiwachwuttikul et al., 2006; Niamsa & Chantrapromma, 1983), stigmasterol (Thitima et al., 2004), aromatic alkene (Tuntiwachwuttikul et al., 2006), 1-allyl-2-methoxy-4,5-metylenedioxybenzene (Tuntiwachwuttikul et al., 2006; Masuda et al., 1991), sarmentide C (Tuntiwachwuttikul et al., 2006), pyrrole amide (Tuntiwachwuttikul et al., 2006), sarmentamide A (Tuntiwachwuttikul et al., 2006), sarmentamide B (Tuntiwachwuttikul et al., 2006), 1-(3,4-methylenedioxyphenyl)-1E-tetradecene (Thitima et al., 2004), horsfieldin (Tuntiwachwuttikul et al., 2006), N-(2-methylbutyl)-2E,4E-decadienamide (Stöhr et al., 1999), naringenin (Subramaniam et al., 2003), cis-caryophyllene (Yan-Ping et al., 2006), hydrocinnamic acid (Niamsa & Chantrapromma, 1983), α-asarone (Likhitwitayawuid & Ruangrungsi, 1987; Yan-Ping et al., 2006; Likhituitayawuid et al., 1988), asaraldehyde (Likhituitayawuid et al., 1988), 1-(3,4-methylenedioxyphenyl)-1E-tetradecene (Likhitwitayawuid & Ruangrungsi, 1987), 2,4,5-trimethoxy-1-propenylbenzene (Yan-Ping et al., 2006), 1-allyl-2,4,5-trimethoxybenzene (Masuda et al., 1991), 1-(1E-propenyl)-2,4,5-trimethoxybenzene (Masuda et al., 1991), 1,2-dimethoxy-4-(1-propenyl)-benzene (Yan-Ping et al., 2006), 1-allyl-2-methoxy-3,4-methylenedioxybenzene (Masuda et al., 1991), 1,3-benzodioxole-4-methoxy-6-2-propenyl (Yan-Ping et al., 2006), 10-epi-γ-eudesmol (Chieng et al., 2005), α-cadinene (Chieng et al., 2005), seychellene (Chieng et al., 2005), δ-cadinene (Yan-Ping et al., 2006), E,E-farnesol (Chieng et al., 2005), 1-nitrosoimino-2,4,5-trimethoxy benzene (Ee et al., 2009), asaricin and myristicin (de Morais et al., 2007).

Pharmacological activities

Antibacterial activities

Extracts of the plant have shown antibacterial activity against Escherichia coli and Bacillus subtilis due to 1-allyl-2,6-dimethoxy-3,4-methylenedioxybenzene (Masuda et al., 1991). Zaidan et al. (2005) have reported that leaf methanol extracts in disc diffusion assay have exhibited antibacterial activity against two Gram positive strains, multi-resistant Staphylococcus aureus and S. aureus, and three Gram negative strains, Klebsiella pneumoniae, Pseudomonas aeruginosa and E. coli. Leaf extracts prepared in 95% ethanol (yield 0.5%) have demonstrated antibacterial activity—in the presence of ultraviolet light exposure at 350 nm for 2 h—against S. aureus and B. subtilis (zones of inhibition ranging 8–12 mm), whereas such extracts have not shown activity against E. coli W, E. coli M and P. aeruginosa (Cheeptham & Towers, 2002). Vaghasiya et al. (2007) have tested methanol extracts of leaves against 15 types of bacterial strains but none of the extracts has shown activity. Leaf oil and 95% leaf ethanol extracts are reported to be inactive against Streptococcus mutans, Lactobacillus sp., Aggregatibacter actinomycetemcomitans and Candida albicans in disc diffusion assay and microdilution method (Taweechaisupapong et al., 2010).

Seven isolated compounds—pellitorine, sarmentine, 1-piperettyl pyrrolidine, pellitorine, guineensine, brachyamide B and 1-(3,4-methylenedioxyphenyl)-1E-tetradecene—from hexane extract of fruit have exhibited antimycobacterial activity, MIC ranging 25–200 µg/mL (Rukachaisirikul et al., 2004). There are other two reports of antimycobacterial activity whereby ethanol extracts of various parts of the plant have shown promising activity and synergistic effect on the activity of isoniazid (Hussain et al., 2008b, 2009a).

Antifungal activity

Different isolated amides from the plant have been evaluated for antifungal activity and in such experiments, a pyrrolidine amide, sarmentosine, has exhibited the activity, IC₅₀ at 32.82 µg/mL (Tuntiwachwuttikul et al., 2006). Leaf extracts prepared in 95% ethanol have demonstrated antifungal activity against Aspergillus fumigatus and C. albicans in the presence of ultraviolet light exposure at 350 nm for 2 h (Cheeptham & Towers, 2002). Essential oil and 95% ethanol extract of leaves have been investigated against four oral pathogens using disc diffusion assay, and in such studies, the oil is reported to be inactive, whereas the extract (0.63 mg/disc) has shown activity only against C. albicans, MBC 1.25 mg/mL (Taweechaisupapong et al., 2010). Extracts of the plant, prepared in 95% ethanol by maceration at room temperature, have been tested against three types of fungi, Aspergillus niger, Aspergillus oryzae and Penicillium sp, and found to be active only against A. niger (Wanchaitanawong et al., 2005).

Antioxidant activities

The plant has been investigated for antioxidant activity using various types of models which are given as follows:

In vitro models: Methanol extracts, prepared by overnight maceration of dried aerial parts of the plant, have shown good antioxidant activity in β-carotene linoleate model, and the activity of the extracts is found to be correlated to their total contents of phenolics, vitamins C and E, tannins, xanthophylls and carotenoids (Chanwitheesuk et al., 2005). Leaf methanol extract of the plant has exhibited antioxidant activity in xanthine/xanthine oxidase scavenging assay, and a flavonoid, naringenin, is determined in active fractions of the extract (Subramaniam et al., 2003). Methanol extract of various parts of the plant is reported to have weak free radical scavenging activity in DPPH model (Hutadilok-Towatana et al., 2006). Aqueous and ethanol extracts of root, stem, leave and fruit have been investigated for antioxidant activity using two in vitro models, β-carotene linoleate model and DPPH model, and these studies have shown that ethanol extracts of leaves and fruit are having good antioxidant activity (Hussain et al., 2009a). Aqueous extracts (10% w/v) of the plant have also exhibited ferric reducing antioxidant power due to their high phenolic contents (Hafizah et al., 2010).

Ex vivo models: Aqueous, methanol and hexane extracts of leaves in a concentration range 100, 150, 250 and 300 μg/mL have shown preservation of the levels of malondehyde, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidise (GPx) in human umbilical vascular endothelial cells (HUVECs) (cell line), during H₂O₂-induced oxidative stress (Hafizah et al., 2010). Ten percent aqueous extract of the plant in a dose of 150 µg/mL has shown marked induction of NO in HUVECs (Ugusman et al., 2010).

In vivo models: Aqueous extract of whole of the plant is found to be effective in relieving streptozotocin-induced oxidative stress in 28-day orally treated rats with a dose, 0.125 g/kg/day (Rahman et al., 2011). Ethanol extracts of leaves and fruit in two dose strengths, 250 and 500 mg/kg/oral, have shown preservation of antioxidant activity against CCl₄-induced oxidative stress in rats (Hussain et al., 2010a).

Hepatoprotective activity

Ethanol extracts of leaves and fruit in doses 250 and 500 mg/kg/day per oral have shown good hepatoprotective activity in rats using CCl₄-induced hepatotoxicity model. The activity has been evaluated by determining and comparing the levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase and total plasma proteins among different groups of animals (Hussain et al., 2010b).

Toxicity and pesticide activity

Leaf oil has shown inhibitory activity against Artemia salina (LC₅₀ 35.2 µg/mL) and 100% mortality in subterranean termite (Coptotermes sp.) within 2 days, at 1% concentration. Moreover, the three isolated compounds such as caryophyllene, myristicin and an unidentified one from the oil have shown significant inhibitory activity against subterranean termite, Coptotermes sp. (Chieng et al., 2008).

Anti-inflammatory and antipyretic activity

Methanolic extracts of leaves at doses 50, 100 and 250 mg/kg have shown significant anti-inflammatory activity with 8.6, 18.6 and 24.7% inhibition of paw edema, respectively, in 3 h, whereas all the three doses have not reduced pyrexia—induced by brewer’s yeast—in rats (Zakaria et al., 2010). Subcutaneous administration of aqueous extracts of the plant has exhibited a dose-dependent anti-nociceptive and anti-inflammatory activity (Rukachaisirikul et al., 2004). Vaghasiya et al. (2007) have also investigated the anti-inflammatory activity of methanol extracts of leaves at a dose 300 mg/kg and noticed 47.41 and 24.78% reduction in paw edema in 1 and 3 h, respectively. In another study, aqueous extracts of leaves have exhibited promising in vivo anti-nociceptive and anti-inflammatory activities (Ridtitid et al., 2007).

Acute oral toxicity

Due to the presence of asarone, a toxic compound, various types of extracts of the plant have been investigated for acute oral toxicity. Ethanol extracts of leaves and fruit have not shown any acute oral toxicity, hence, LD₅₀ of both the extracts is found to be much higher than a limit dose, 2000 mg/kg (Hussain et al., 2010a). Aqueous extracts of the plant are reported to be safe below 10 g/kg dose, whereas a number of deaths have occurred in rats at doses equal to or more than 10 g/kg (Peungvicha et al., 1998). Ridtitid et al. (2007) have reported that methanol extracts of leaves at dose 5 g/kg in mice are not having any mortality.

Cyclooxygenase and lipoxygenase inhibitory activity

In cyclooxygenase and lipoxygenase inhibitory activity studies, two amides, isobutylamide and methylbutylamide, isolated from hexane extract of aerial parts of the plant have exhibited cyclooxygenase-1 (COX 1) and lipoxygenase-5 (LOX 5) inhibitory activities with IC₅₀ at 19 and 10 µg/mL, respectively (Stöhr et al., 1999). Stöhr et al. (2001) reported that hexane extracts of the plant have COX 1 inhibitory activity (71 ± 12%) and LOX 5 inhibitory activity (28 ± 16%).

Larvicidal activity

Dichloromethane and methanol extracts of leaves of the plant are reported to have promising larvicidal activity, in brine shrimps model (Satariah, 2005). Extracts of aerial parts of the plant that have been prepared by successive maceration in three lifters of 95% ethanol for 3 days have exhibited efficacy against fourth instar larvae of Aedes aegypti mosquito using larvicidal bioassay, MIC at 4.06 µg/mL (Chaithong et al., 2006), whereas, in another study, extracts of aerial parts of the plant, prepared by successive maceration in the same solvent for 7 days, have exhibited activity against Stegomyia aegypti, a main vector of dengue and dengue hemorrhagic fever, with LD₅₀ at 0.14 µg/mL/female (Choochote et al., 2006). The essential oil of leaves of the plant is reported to be active against larvae of A. aegypti with LC₅₀ = 36 μg/mL and LC₉₀ = 47 μg/mL (de Morais et al., 2007). There are two more reports of insecticidal activity of extracts of the plant (Lay, 1988; Bee, 1997).

Antineoplastic activity

Toong and Wong (1989) have reported the antineoplastic activity of extracts of the plant that is attributed to a sterol, β-sitosterol. There is another report indicating anticancer properties of ethanolic extract of leaves on HepG2 cell line and non-malignant Chang’s liver cells with IC_50s 12.5 µg/mL and IC₅₀ 30 µg/mL, respectively (Ariffin et al., 2009).

Antipsychotic activity

Methanol extracts of leaves of the plant in a concentration range 3.2, 4, 4.8 and 6.4 mg/mL have exhibited a transient increase in twitch tension of rat phrenic nerve hemidiaphragm preparation which is followed by a marked dose-related neurally evoked twitch depression with EC₅₀ at 4.07 mg/mL (Ridtitid et al., 1998).

Antiprotozoal activity

Crude methanol extract of root upon oral administration, dose 1000 mg/kg/day, for 5 days has shown 40% curative rate in mice suffering from Entamoeba histolytica infection, while the administration of lower doses such as 500 and 250 mg/kg/day is found to be ineffective (Sawangjaroen et al., 2004). Chloroform extract of the plant has exhibited 86.30% inhibition of malarial parasite at a dose of 0.1 mg/mL, while a complete inhibition of the parasite is noticed at a concentration of 0.4 mg/mL (Najib Nik A Rahman et al., 1999). In a comparative study, chloroform and methanol extracts of leaves have shown complete inhibition of plasmodium in 48 h at a doses 0.05 and 0.08 mg/mL, respectively (Najib, 1999). Rukachaisirikul et al. (2004) have reported that two isolated amides, sarmentine and 1-piperettyl pyrrolidine, from hexane extracts of fruit have also exhibited antiplasmodial activity with IC₅₀ 18.9 and 6.5 µg/mL, respectively.

Hypoglycemic activity

Aqueous extracts of whole of the plant in single oral doses 0.125 and 0.25 mg/kg have shown significant reduction in plasma glucose level in streptozotocin-diabetic rats, and a significant effect is reported after 7 days treatment at a dose 0.125 mg/kg (Peungvicha et al., 1998).

Anti-atherosclerosis activity

A freeze–dried aqueous extract of leaves in doses 62.50, 125.00 and 500 mg/kg upon administration to rabbits that are being fed with diet containing 1% cholesterol results in reduction in the levels of inflammatory markers, vascular cell adhesion protein-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and C-reactive protein. And in this study, a significant reduction in inflammatory markers is observed in animals, receiving a dose 500 mg/kg (Amran et al., 2011). In another report, freeze–dried aqueous extract of leaves in a dose 500 mg/kg has shown significant reduction in fatty acid streak under Sudan-IV stain, and electron transmission microscopy has indicated reduction in foam cells on atherosclerotic lesions (Amran et al., 2010). The effect of extracts on bone resorption and its relationship to plasma cortisol levels in rats are reported by Ima-Nirwana et al. (2009).

Expression of cellular adhesion molecules

The effect of aqueous extract of leaves in a dose 150 µg/mL on gene expression of nuclear factor κB, VCAM-1, ICAM-1, E-selectin, NADPH oxidase-4 (Nox4), SOD1, CAT and GPx in cultured HUVECs has been investigated, and the extract is found to be reducing mRNA expression of ICAM-1 and Nox4. Moreover, the extract is found to be upregulating the mRNA expression of SOD1, CAT and GPx, whereas no significant change has been observed in the mRNA expression of VCAM-1 and E-selectin (Ugusman et al., 2011).

Propellant activity

Petroleum ether extracts prepared from dried leaves using soxhlet have shown moderately high propellant activity (53.28% relative oviposition) against 15-day-old adult flies, Dacus dorsalis (Areekul et al., 1998).

Antiangiogenic activity

Different types of extracts of the plant have been investigated for antiangiogenic activity in rats by aorta ring assay, and among all the extracts, chloroform extract is found to be having significant antiangiogenic activity with IC₅₀ 45 µg/mL (Hussain et al., 2008a). The same extract has been evaluated for toxicity, chemical analysis, pharmacokinetics and stability (Hussain et al., 2009c).

Cytotoxicity

Different concentrations of chloroform extract obtained from sequential extraction of leaves have exhibited cytotoxicity on human hepatic carcinoma cell line (HepG2) and HUVECs using MTT cell viability assay with IC_50s 76.24 µg/mL and IC₅₀ 64.43 µg/mL, respectively (Hussain et al., 2009b). There is another report in which leaf extracts prepared by maceration in 80% v/v ethanol have shown cytotoxicity to HeLa cells with CD₅₀ at 0.1 mg/mL (Ali et al., 1996).

Antiviral activity

Leaf extracts prepared by maceration in 80% v/v ethanol have been tested for antiviral activity using two types of viruses, herpes simplex virus-1 (HSV1) and vesicular stomatitis virus (VSV), and the extracts are found to be inactive against HSV1, whereas active against VSV with MIC at 0.02 mg/mL (Ali et al., 1996).

Fracture healing

Freeze–dried aqueous extracts of leaves are reported to be improving fracture healing in estrogen-deficient rats that has been confirmed upon observing radiological changes in fracture calluses, assessed by reduced callus volumes and reduced callus scores (Estai et al., 2011).

Reduction of toxicity of cigarettes

Cigarette filters having a combination of herbs including P. sarmentosum have shown the potential of reducing toxicity and mutagenicity of the cigarettes (Wei et al., 2007).

Allelopathic activity

Leaf extracts prepared in 80% v/v aqueous methanol have been investigated against 12 plant species in a concentration range 0.01, 0.03, 0.1 and 0.3 g/mL and found to be variably inhibiting the growth of the plants that has been evaluated in this experiment (Pukclai & Kato-Noguchi, 2011). Bacterial isolates from root of P. sarmentosum have shown the ability to produce plant hormone, indole-3-acetic acid (Nimnoi & Pongsilp, 2009).

Nutritional value

The plant has been evaluated for nitrate, nitrite and vitamin C contents, and based on lower content of the former two and higher content of the latter one, the plant is recommended as an edible vegetable (Qui & Zeng, 2006). Moreover, the plant is not found to have anti-nutritive factors such as cyanide and inhibitors of trypsin and chymotrypsin (Yeoh & Wong, 1993). The plant is found to have good nutritive value due to high contents of proteins (Ching & Mohamed, 2001) and carbohydrates as well as primary and secondary metabolites (Hussain et al., 2008b, 2009a). Leaves contain α-tocopherol, 10.02% of dry mass and 5.97% of fresh mass (Ching & Mohamed, 2001). The plant is rich in protein, amino acids, minerals, sugars, lipids and fiber (Ching & Mohamed, 2001). Recently, another antiobesity composition made from the plant has been patented (Ismail & Hussain, 2011).

Pharmacokinetic studies

Ethanol extract of fruit in an oral dose of 500 mg/kg has been investigated for pharmacokinetics in rats using three markers, pellitorine, sarmentine and sarmentosine, and among such markers, the former two have exhibited good oral bioavailability, tissue distribution and excretion in urine, whereas the latter one has zero oral bioavailability and has been excreted in fecal matter (Hussain et al., 2011b).

Analytical studies

From essential oil of leaves, more than 67 compounds were separated, identified and the major ones found to be 2,4,5-trimethoxy-1-propenylbenzene 23.20%, cis-caryophyllene 13.33%, 1,2-dimethoxy-4-(1-propenyl)-benzene 12.63%, 1,3-benzodioxole-4-methoxy-6-(2-propenyl) 5.71% and δ-cadinene 3.03% (Yan-Ping et al., 2006). Another study indicated that leaves had 1.10% v/w essential oil that upon GC-MS analysis indicated the presence of 31 components, the major ones included 10-epi-γ-eudesmol 21.0%, α-cadinene 18.8%, seychellene 12.6% and (E,E)-farnesol 10.5% (Chieng et al., 2005). A HPLC method was developed for the quantification of pellitorine, sarmentine and sarmentosine in various types of extracts of the plant, plasma, tissues, urine, and fecal matter (Hussain et al., 2011b). Another method for the quantification of aforementioned three compounds in extracts was developed using GCTOF-MS by Hussain et al. (2009g). An HPLC method for simultaneous determination of piperine and flavonone in extracts of the plant was developed using gradient elution. Additionally, the extracts of the plant have been analyzed for the estimation of primary and secondary metabolites (Hussain et al., 2008b, 2009a). Crude powders of various parts of the plant have been investigated for number of physicochemical and proximate analyses (Hussain et al., 2009f). Variation in metabolites of the fruit in different seasons has been described by Hussain et al. (2009e) using FTIR fingerprint profiles. Extraction efficiency of various solvents including supercritical CO₂ for total amide contents and pellitorine, sarmentine and sarmentosine has been described indicating the similarity in extraction potential of ethanol by reflux and supercritical CO₂ (Hussain et al., 2010c). Ching and Mohamed (2001) have quantified α-tocopherol in leaf extracts, prepared using solvent system comprising 900 mL hexane, 100 mL ethyl acetate and 20 mg butylated hydroxytoluene using HPLC, and the contents of α-tocopherol are found to be 10.02 and 5.97% with reference to dry mass and fresh mass, respectively.

Stability studies and chemical kinetics

There are only two reports about the investigation of extracts for accelerated stability studies to assign the shelf life and calculation of kinetic parameters. In one study, stability studies are carried out analyzing metabolomic fingerprint profiles, obtained from UV/Vis spectroscopy and HPTLC (Hussain et al., 2009d), whereas, in the other study, pellitorine, sarmentine and sarmentosine are used to determine kinetic parameters and stability at various storage conditions, and prediction of shelf life at room temperature using Arrhenius equation (Hussain et al., 2011a).

Patents and commercial products

The aerial parts of the plant in a proportion of 19.05% with some other herbs and gypsum are used to prepare an external adhesive plaster that has been proved to be efficacious and nontoxic, Patent No. CN 1117394A (Lu, 1995). Liquor made from certain herbs including P. sarmentosum is being recommended for rheumatoid arthritis, arthralgia, rheumatic numbness, rheumatalgia and traumatic injury, Patent No. CN 1813922 (Zihua, 2006).

Conclusion

The present review provides a summarized literature regarding botanical, phytochemical, pharmacological, analytical, and stability data of P. sarmentosum, which may be helpful to researchers, intending to investigate the plant in future, and natural pharmaceutical industry, desiring to prepare stable and evidence-based formulations from the plant. The review has revealed the scientific evidence that supports various traditional claims, and safety as a food. Some of the investigations indicate new therapeutic uses of the plants. The antiangiogenic activity and toxicity studies of extracts of the plant on different types of cell lines indicate the potential of the plant in treating diseases involving neo-vascularization. Last but not least, efficacy, safety, pharmacokinetic and stability data of the plant urge investigation of various types of extracts of the plant for clinical studies.

Declaration of interest

The authors report no conflicts of interest.