Trichosanthes dioica Roxb.:A vegetable with diverse pharmacological properties

Mhi KhndkerSleh AkterMohmmd Zfr Imm

aDepartment of Biotechnology,Bangabandhu Sheikh Mujibur Rahman Agricultural University,Salna,Gazipur 1706,Bangladesh

bDepartment of Pharmacy,Primeasia University,HBR Tower,9 Banani,Dhaka 1213,Bangladesh

cDepartment of Pharmacy,Stamford University Bangladesh,51 Siddeswari Road,Dhaka 1217,Bangladesh

Abstract

Keywords:Trichosanthes dioica;Pointed gourd;Cucurbitaceae;Ethnomedicine;Ethnopharmacology

1.Introduction

Cucurbitaceae is a large family of vegetable crops[1].The members of this family are annual or perennial herbaceous vines and are mostly found in tropical and subtropical areas with few species in temperate regions[2].According to The Plant List(http://www.theplantlist.org/), the most comprehensive on-line plant name database[3–5],Cucurbitaceae family comprises of 134 genera and 965 species.However,the numbers significantly vary among other reports by Jeffrey[6],Kumar,et al.[7],Payel,et al.[8]and Christenhusz and Byng[9].TrichosanthesL.genus of the Cucurbitaceae family comprises of 38 species(http://www.theplantlist.org/).

Trichosanthes dioicais annual or perennial herbaceous vine commonly known as Pointed gourd(English),Putulika(Sanskrit),Parval(Hindi)and Potol(Bengali).It grows up to 5–6m.The stem is about 1cm thick with simple tendrils.The leaves are cordate,oblong,acute,sinuate-dentate not lobed and dark green[10].The inflorescence is racemose and the flowers found in leaf axils are whitish green,sessile,solitary,bracteate with oblong-cylindrical calyx tube[11].Fruits are generally globose,oblong and smooth and the pericarp and mesocarp form the edible part[11].The shape,size and striation patterns of the fruit vary greatly giving rise of four categories:(1)10–13cm long fruit of dark green color with white stripes;(2)10–16cm long and comparatively thick fruit with dark green color with very pale-green stripes;(3)5–8cm long and roundish fruit of dark green color with white stripes;and(4)5–8cm long fruit of green color,tapered at the ends,and striped[11,12].T.dioicahas tuberous taproots.The propagation usually is done by root or stem cuttings rather than the seed because of poor germination and late flowering[11].

Trichosanthes dioicaRoxb.is one of the most consumed species ofTrichosanthesgenus in the Asian tropical countries particularly in Bangladesh and India as a vegetable from February to September[11].T.dioicais thought to be originated in the Indian subcontinent or Indo-Malayan region[12–15].It is mainly cultivated in Bangladesh,India,Pakistan,Myanmar,Nepal and Sri Lanka[16,17].

The unripe fruit is cooked either alone or with other vegetables or meat[12].It is a very nutritious vegetable which also has potential for industrial use in making different types of jam,jelly,and pickles[18].There is an increasing demand of this vegetable in the ethnic grocery stores of the different parts of the world[11].Different parts of this species are been used by the folk practitioners and in a number of Ayurvedic preparations.Numerous studies have been performed to evaluate the validity of the traditional uses.Due to its heavy consumption as vegetable and its different folkloric uses,the present review aims to present the ethnobotanical uses,advances in ethnopharmacological studies and phytochemistry of different parts ofT.dioica.

2.Methodology

Available original research,reviews,and reports onT.dioicawere consulted from published scientific peer-reviewed journals and books.Literature was searched in a number of electronic databases namely, PubMed, Web of Science and Google Scholar using specific keywords such as “Trichosanthes”,“Trichosanthes dioica”,“pointed gourd”,“putulika”,“parval”,“parwal”,“patol”and “potol”.These keywords were searched individually as well as in combination where appropriate to get all relevant works published up to August 2017.The literature was then screened and only those pertaining to theT.dioicawere selected.The literature was critically read and the scientific information on the species has been collated in this review.

3.Ethnobotanical uses

T.dioicais used in the Ayurveda as well as by the rural and tribal folkloric practitioners in a number of human ailments(Table 1).In Ayurveda,it is used alone or in combination with other herbs to treat hyperacidity[19].Nadkarni and Nadkarni[20]described its use as antiparasitic,antiperiodics,febrifuge,refrigerants,anticoagulants,blood purifiers,antiseptics,and tonic.Decoction of leaves mixed withPiper nigrumfruit powder is used to treat diarrhoea[21].The plant is also used as stomachic,antitumor and antidiabetic agent[22].In Ayurveda leaves and fruits ofT.dioicais used to treat alcoholism and jaundice[7,23].Fruit is also used in improving appetite and digestion[24].

Table 1Traditional uses of T.dioica.

The raw fruit juice is taken as a remedy for spermatorrhoea[25]while the juice of roasted fruits is applied on chicken pox scar[26].T.dioicafruit boiled withCoriandrum sativumseed andTerminalia chebulakernel is taken in the treatment of teeth and fruit skin juice mixed with honey is used to remove the bad odor of mouth[27].Fruits are also used in fungal infection in nails and decoction of leaves withTerminalia chebulaandCoriandrum sativumis taken to treat acidity with constipation[28].The root ofT.dioicais used to treat jaundice,ascites,anasarca and as a febrifuge,tonic and hydragouge cathartic[25,29].

4.Pharmacology

4.1.Antihyperglycemic activity

The effect ofT.dioicaon hyperglycemic conditions in animals has been studied quite extensively(Table 2).Antihyperglycemic activity of the fruit ofT.dioicawas first reported by Sharma and Pant[35]in normal albino rabbits.After a decade later Rai,et al.[36]reported the antihyperglycemic activity of the aqueous fruit extract ofT.dioicain streptozotocin(STZ)-induced diabetic rats.In this study,the extract was orally administered at a daily dose of 1000mg/kg body weight in rats for 28 consecutive days.After treatment,significant reduction was observed in all of the tested parameters viz.fasting blood glucose(FBG)(28.7%),postprandial glucose(PPG)(30.7%),aspartate aminotransferase(AST)(22.6%),alanine aminotransferase(ALT)(36.5%),alkaline phosphatase(ALP)(34.2%),serum creatinine(SC)(35.3%),urine sugar and urine protein.In continuation to this work Rai,et al.[37]selected multiple doses such as 500,750,1,000,and 1,250mg/kg body weight for further study.The results were significant in terms of reducing the FBG in normoglycemic rats at 6h observation and in oral glucose tolerance test(OGTT)at 4h observation.The glucose level was reduced in sub-diabetic and mild-diabetic rats at all the doses.However,the largest tested dose,1250mg/kg,did not show a significant reduction in mild-diabetic rats.Severe diabetic rat models were also used to evaluate the effect by Rai,et al.[38].A significant reduction was observed in FBG and PPG in 28days study period.

Table 2Summary of pharmacological studies and activities of T.dioica.

Rai,et al.[39] also studied the antihyperglycemic potential of seed extract ofT.dioicaat the dose range of 500–1250mg/kg in normal,sub-diabetic and mild diabetic rats.The extract showed a dose-dependent fall of FBG up to 1000mg/kg dose in normoglycemic rats.The effect was similar in case of STZ-induced sub-diabetic and mild diabetic rats in OGTT.Interestingly,the antihyperglycemic effect at 1000mg/kg was better than that shown by 1250mg/kg dose and the effect was similar or better to the effect given by standard drug tolbutamide[39].However,the possible reason for the better effect of 1000mg/kg dose over 1250mg/kg is absent in the literature.

The leaves ofT.dioicahave also been evaluated in normal as well as in diabetic animal models for its hypoglycemic potential.Oral administration ofT.dioicaleaf extract at the doses of 250,500,and 750mg/g in normal and STZ-induced sub-and milddiabetic rats showed promising hypoglycemic potential[13].Interestingly,the dose of 500 mg/kg was found to be more effective than 750mg/kg.It lowered the FBG level by 32.9% at 6h in normal rats while it reduced the level by 30.9% in OGTT at 5h.The effect of the extract was more pronounce in sub-and mild-diabetic mice as it reduced the glucose level by 40.3 and 86.6% respectively in OGTT at 3h period[13].The leaf extract was also studied at 800 and 1600mg/kg doses and were found effective in both normoglycemic and diabetic rats after both single dose and repeated administration[40].A significant loss in weight in the two-week observation period was also reported[40].So it appears that the leaf alongside fruits and seeds ofT.dioicapossess significant antihyperglycemic property.

4.2.Antihyperlipidemic activity

4.2.1.Animal studies

Four animal studies have been found reporting the effectiveness ofT.dioicaon lipid profile(Table 2).Sharma and Pant[35]studied the antihyperlipidemic potential ofT.dioicafruit in normal albino rabbits(n=8).1g of fruit powder mixed with 100g of rabbit feed were used for the experimental animals where the daily feed consumption ranged between 95–100g.The treatment has shown hypocholesterolemic and hypotriglyceridemic effect.It also increased phospholipids and HDL-cholesterol in rabbits[35].Similar improvement in lipid profile has also been shown by the seed extract ofT.dioica[41].

The aqueous fruit extract ofT.dioicaalso showed a hypocholesterolemic and hypotriglyceridemic effect in normoglycemic and STZ-induced diabetic rats after a single treatment at the dose of 50mg/kg[30].The hypocholesterolemic effect was similar upon repeated treatment for 2 weeks in both models.Though the triglyceride(TG)levels increased for a couple of days,eventually it decreased significantly afterward that was persistent up to 2 weeks.The body weight of animals of both groups also significantly decreased after 2 weeks’treatment[30].The effect of fruit extract at 1000mg/kg dose was also tested in severely diabetic rats for a period of 4 weeks[38].Total cholesterol(TC)and TG level reduced by 57.2 and 18.5% respectively after 4 weeks treatment.On the other hand,HDL level was increased by 33.0% whereas low-density lipoprotein and very low-density lipoprotein level were decreased by 9.6 and 57.2%,respectively[38].

4.2.2.Human study

Sharma,et al.[42]carried out a human trial to observe the antihyperlipidemic activity of seed ofT.dioica.A group of mild diabetic male human(n=20)with no previous history of diabetes(FBS:83.35±6.09;age:20–42 years;weight:49–60kg)were given 7g of seed powder ofT.dioicadaily for two weeks.The lipid profiles of this group were compared with a group of non-diabetic human subjects(n=20)(FBS:117.12±5.34;age:32–62 years;weight:55–69kg)receiving the same treatment.The treatment significantly decreased the serum level of cholesterol and TG and increased phospholipids level in diabetic patients.The increase of HDL-cholesterol was also noticeable.All the parameters were also improved in the non-diabetic group in comparison to their biochemical parameters before receivingT.dioicatreatment.This unbiased overall improvement in lipid profiles in both human groups provides evidence for the potential use ofT.dioicaseed in humans in dyslipidemia.

4.3.Antitumor activity

It has been reported that hydroalcoholic extract ofT.dioicaroot has antitumor and oxidative stress-reducing activity in Ehrlich ascites carcinoma(EAC)cells in mice at 5 and 10mg/kg doses(Table 2).Mice were intraperitoneally injected with EAC cells and after 24 hT.dioicawas administered at 5 and 10 mg/kg doses and the treatment were continued for 9 days[44].Observation on the 10th day showed thatT.dioicatreatment significantly decreased tumor weight, tumor volume, packed cell volume and viable cell count as well as extended the lifespan of test animals and hematological parameters were improved[44].Hepatic antioxidant parameters such as lipid peroxidation,reduced glutathione(GSH),glutathioneS-transferase(GST),superoxide dismutase(SOD)and catalase(CAT)were also significantly improved in theT.dioicatreated group[44].The triterpenoid fraction ofT.dioicaroot has also been tested at 2 and 4mg/kg doses in the same model and its antiproliferative efficacy has been reported[43].All these results indicate antitumor efficacy ofT.dioicaroot(Table 2).

It is very interesting that the same extract has been reported to promote tumor proliferation in EAC in mice by the same researcher group[34].It this case,mice were intraperitoneally injected with EAC cells and after 24hT.dioicawas administered at 5 and 10 mg/kg doses and the treatment were continued for 8days[44].Tumor proliferation,hematological and hepatic examination have shown a significant increase in tumor weight as well as volume,packed cell volume and reduced non-viable cells and lifespan of test animals,worsened hematological and hepatic antioxidative parameters[44]. Both reports used the very same experimental model and procedure, used only higher doses of extract,and found to possess completely opposite effect!The possible mechanism was not explained.However,trichosanthin,a ribosome-inactivating protein,isolated from the root ofT.dioicahas been found to induce apoptosis in tumor cells[61,62].

4.4.Ameliorative effect on arsenic toxicity

Effect ofT.dioicaon arsenic-induced toxicity has been studied on different organ system and was found effective in all the studies.The hydroalcoholic extract ofT.dioicaroot was evaluated at 5 and 10mg/kg doses for its potential ameliorative effect against arsenic-induced toxicity in rats.T.dioicawas orally administered for 20 consecutive days and then sodium arsenite for 8 days.T.dioicatreatment showed significant ameliorative effect on body weight,renal and kidney weight,hematological and serum biochemical profile and hepatic and renal biochemical parameters against arsenic toxicity[48].Aqueous extract ofT.dioicafruit was also tested in a similar model at the doses of 50 and 100mg/kg with arsenic exposure to 10 days.Significant ameliorative effect was shown by the fruit extract also[45].The fruit extract has also alleviated arsenic-induced brain toxicity[46]and myocardial toxicity[47].The root extract also alleviated myocardial toxicity[49].

4.5.Anti-inflammatory activity

The fruit ofT.dioicawas tested for anti-inflammatory effect in carrageenan-induced paw edema in rats[50].Methanolic extract was tested at 100,200,and 400mg/kg doses and dichloromethane and ethyl acetate fractions were tested at 200mg/kg doses.Methanolic extract at 200 and 400mg/kg doses and ethyl acetate fraction showed a significant decrease in paw diameter.The dichloromethane fraction did not inhibit the paw diameter significantly[50].

The root extract ofT.dioicahas also shown promising antiinflammatory activity in both acute and chronic inflammation model in rats at the doses of 50 and 100mg/kg[32].The extract reduced the carrageenan-induced paw edema in a dosedependent manner after 4h.Besides,it improved the edema induced by histamine and serotonin indicating that it also suppresses inflammation induced by inflammatory mediators.T.dioicahas also significantly reduced cotton pellet induced granuloma formation[32].The same extract was tested at 25,50,and 100mg/kg doses in formalin-induced acute inflammatory ascites in rats and the extract significantly reduced the ascitic fluid formation after 7 h in a dose-dependent manner[51].These demonstrate the anti-inflammatory potential ofT.dioicaroot extract in different inflammatory animal models.

Ethanolic extract of aerial parts ofT.dioicaand its successive petroleum ether,chloroform,ethyl acetate,and methanolic fractions have been evaluated for anti-inflammatory effect at 150 and 300mg/kg doses in carrageenan-induced paw edema test in rats[52].Except for petroleum ether fraction,all samples showed a significant reduction in paw volume after 5h posttreatment.Extract and fractions have been found to attenuate tumor necrosis factor-α (TNF-α)level as well as reduced expression of cyclooxygenase-2 and nuclear transcription factor-κB and the ethyl acetate fraction was reported to be the most effective against inflammation and attenuation of TNF-α[52].

4.6.Gastrointestinal effects

Akter,et al.[53]evaluated the antidiarrheal potential of aerial parts ofT.dioicain castor oil and magnesium sulphate-induced diarrhea in mice.Four different extracts of the plant material were used namely petroleum ether,ethyl acetate,methanol and water extract at 200 and 400mg/kg doses.All four extracts showed a significant decrease in castor oil-induced fecal droppings whereas the effect of ethyl acetate and methanol extracts in magnesium sulphate-induced diarrhea was significant[53].

Bhattacharya and Haldar[58]have tested the laxative potential of the aqueous extract ofT.dioicaroot in mice.The extract at 100 and 200mg/kg doses were tested in both non-constipated and loperamide-induced constipated mice[58].Gastrointestinal(GI)transit was also measured.Both doses caused a significant increase in total stool and wet stool up to 4h observation in a dose-dependent manner.The extract also increased GI transit time suggestingT.dioicaroot extract possesses stimulant laxative activity.Observing the effect Bhattacharya and Haldar[59]carried out the further study with the triterpenoid enriched fraction in same mice models at 50 and 100mg/kg doses.The triterpenoid fraction ofT.dioicaroot showed promising laxative and prokinetic effects.

4.7.Antinociceptive activity

The triterpenoid-enriched extract ofT.dioicaroot has been evaluated for antinociceptive activity at 50 and 100mg/kg doses by acetic acid-induced writing and tail flick test in mice.The number of writhing was significantly inhibited by both 50 and 100mg/kg doses while only 100mg/kg dose significantly increased the latency period in tail flick test[32].The dichloromethane and methanol extract of roots ofT.dioicawere also tested for antinociceptive activity at 75 and 150mg/kg doses.Acetic acid-induced writhing was significantly inhibited by both doses of dichloromethane and only by 150mg/kg dose of methanol extract.In tail flick test only dichloromethane extract at only 150mg/kg dose significantly increased latency period 1h post-treatment[33].

4.8.Antioxidant activity

Differentin vitroantioxidant assays have been performed with various parts ofT.dioicaand a promising antioxidant profile ofT.dioicahas been reported.The leaf extract has been reported to possess promising ferrous reducing antioxidant power and phenolic compounds were estimated as 259mg/g[63].Aerial parts ofT.dioicahas also shown antioxidant activityin vitroin nitric oxide scavenging[53].Fruit extracts and different fractions have shown antioxidant activity in DPPH radical scavenging,nitric oxide scavenging,and reducing power assay in a dose-dependent manner[50,64].

4.9.Cytotoxic activity

In vitrocytotoxic activity of dichloromethane,methanol and aqueous extract ofT.dioicawas evaluated usingAllium ceparoot meristems growth test. Dose-dependent inhibition of root growth and reduction of the mitotic index was observed in case of all extracts amongst which dichloromethane extract was found most potent with EC50of 2.8mg/ml[29].These results demonstrate cytotoxic and genotoxic potential ofT.dioicaextracts[55].

4.10.Hepatoprotective activity

Hepatoprotective potential ofT.dioicawas evaluated in ferrous sulphate-induced hepatotoxicity in a rat model.Aqueous and ethanolic extract ofT.dioicaat the doses of 100,200,and 400mg/kg were administered for 10days and then ferrous sulphate at the dose of 30 mg/kg was administered intraperitoneally to induce hepatotoxicity[56].On 11th day blood was tested for different hepatic parameters such as alanine aminotransferase(ALT),aspartate aminotransferase(AST),alkaline phosphatase(ALP),total protein(TP)and total bilirubin(TB)and histopathological examination was performed.Both extract at 200 and 400mg/kg doses significantly decreased the level of ALT,AST,ALP,and TB and increased TP.Histopathological examination showed that aqueous extract ofT.dioicaat 200mg/kg dose showed slight evidence of necrosis and at 400mg/kg dose there was no infiltration and no necrosis whereas the ethanolic extract treatment at both 200 and 400mg/kg doses showed no infiltration,necrosis or degenerative changes[56].

4.11.Chemopreventive activity

Chemopreventive potential of hydroalcoholic extract ofT.dioicaroot was evaluated against 3-methylcholanthrene(3-MC)-induced carcinogenesis in mice at the doses of 2 and 4mg/kg for 45 days.The treatment was orally given after 24h of single-dose 3-MC(200μg)administration subcutaneously in mice.After 15 weeks hematological and hepatic profiles were observed and it has been found thatT.dioicareduced tumor incidence in mice and both hematological and hepatic parameters(lipid peroxidation,reduced glutathione,glutathione-S-transferase,superoxide dismutase,and catalase)have significantly been improved indicating the extracts chemopreventive potential[54].

4.12.Immunomodulatory effect

Aqueous extract ofT.dioicawhole plant was administered in rats at the dose of 100 and 200mg/kg doses for 45 days.The extract has shown increased production of red blood cells,white blood cells,and hemoglobin.A dose-dependent increase in antibody production was also observed indicating the immunomodulatory effect of the extract[57].

4.13.Wound healing activity

Shivhare et al.[60]have studied the wound healing activity ofT.dioicain excision and incision rat models.T.dioicaointment(5% w/w)was administered to the rat models and the results of the study showed improvement in all the parameters such as wound contraction,epithelialization period,tensile strength,and hydroxyproline content.While tensile strength assured the mechanical strength of the healed wound,hydroxyproline content in the collagen fibers helped to understand the progression of the healing process.Histopathological examination of the skin sample presented significant presence of fibroblast cells,collagen fibers,and blood vessels[60].

4.14.Antipyretic activity

Antipyretic activity ofT.dioicafruit extract was tested in rats with Brewer’s yeast-induced fever.Methanol extract at 400mg/kg dose and ethyl acetate fraction at 200mg/kg dose showed significant antipyretic activity from 3rd to 5th h of treatment[50].

4.15.Antifungal activity

The unsaponifiable fraction of the fixed oils ofT.dioicaseed has shown antifungal activity using filter paper disc plate method[65].

4.16.Neuropharmacological activity

The extract of roots ofT.dioicawas also tested for CNS depressant activity at 75 and 150mg/kg doses in mice.The effect of dichloromethane and methanol extract on the locomotion of mice was observed using actophotometer.Only dichloromethane extract showed a dose-dependent decrease in the locomotion significantly[33].Bhattacharya and Haldar[66]have also reported that the root extract has skeletal muscle relaxant and sedative property.

4.17.Antiulcerant activity of polyherbal preparations containing T.dioica

T.dioicaalong with other medicinally important herbs are used to prepare Ayurvedic preparation.One such preparation has been studied in peptic and duodenal ulcer patients.In a 10-patient case study of peptic ulcer disease(PUD),a preparation containing eleven herbs includingT.dioicashowed complete improvement in 50% cases and partial improvement in 40% cases[19].The treatment was given at the dose of 10ml thrice daily for 3 weeks.It decreased gastric acid hypersecretion and normalized hyposecretion.Another polyherbal formulation of four herbs includingT.dioicahas also showed antiulcerant activity where 33 operated cases of duodenal ulcers(DU)were treated with 20ml twice daily dose.Moreover,single herbT.dioicahas also proved efficacy in 20-patient case of DU at the dose of 50 ml thrice daily for three weeks[19].All these studies can be a strong evidence for the antiulcerant potential ofT.dioica.

5.Toxicology

T.dioicafruit is mainly consumed as a vegetable along with seed in tropical Asia. No report of toxicity of the fruits in humanhas been documented. There is only one report that evaluated the toxicity of the seeds ofT.dioicain male albino Wistar rat.The rats were given 10 and 15g of the extracts and were observed for gross behavioral neurologic,autonomic,and toxic effects constantly.Consumption of foods,feces,and urine were also examined at 2h and then at 6-h intervals for 24h.Behavior of the treated rats appeared normal with no toxic effect at doses up to 10 and 15-times the effective dose and no death in any of these groups were observed[39].Besides,T.dioicaroot extracts have shown wormicidal activity againstPheretima posthumaandAscaridia galli[67].

6.Phytochemistry and bioactive compounds

Phytochemical analyses of different parts ofT.dioicahave led to isolation of great number of compounds(Table 3)(Fig.1).Chopra,et al.[68]reported the presence of trichosanthin inTrichosanthesabout sixty years ago.Trichosanthin has also been found in the root ofT.dioicawhich is known as a ribosomeinactivating protein(RIP)and for its anti-HIV activity[23,69].Besides,significant amount of peptides,ranging in 2–8kDa,have been isolated from the seeds ofT.dioica[70].These peptides are unique in nature being resistant to silver nitrate’s action which generally stains protein[70].Lectin,a carbohydratebinding protein,has been found in the seeds ofT.dioicausing affinity chromatography on cross-linked guar gum[71].This protein is galactose-specific and it consists of two subunits of 37 and 24kDa size covalently connected by disulfide bond[71].This lectin is thought to be similar to type-2 RIP considering its subunit size,disulfide linkage,galactose-specificity and secondary structure[71].

Table 3Compounds reported in different parts of T.dioica.

Fig.1.Chemical structures of major compounds in T.dioica.(Structures were obtained from the PubChem database at https://pubchem.ncbi.nlm.nih.gov/).

Fig.1.(Continued)

Sterols and tetra-and pentacyclic triterpenes are the most abundant group of chemical compounds found inT.dioica.In the late nineties,14 sterols and 13 triterpenes were isolated from the unsaponifiable lipids from the root(Table 3)and the composition was compared with the other cucurbits[72,73].Euphol,α-amyrin,β-amyrin,lupeol,and taraxerol are the most important bioactive triterpenes among them.The same group of researchers also reported the isolation of another six triterpenes including betulin and karounidiol from seed[74].Cucurbitacin B,an oxygenated tetracyclic triterpenoid,with promising anticancer potential has been found in the fruit[75].

A steroidal saponin namely 24-α-ethyl-20-ene-7-hydrostigmast-8β:14β-di-3-O-β-D-xylofuranoside has been found in the leaf[22].The leaf also contains phenols and flavonoids which have been quantified[63,76].

The fruit has been reported to contain a higher concentration of calcium,magnesium,iron[37],and free amino acids,nicotinic acid,riboflavin,vitamin C,thiamine,5-hydroxytryptamine[25].It has been reported that root contains colocynthin,hentriacontane,cucurbita-5,24-dienol[25],an amorphous saponin,a non-nitrogenous bitter glucosidic principle,essential oil,fixed oil and tannin[10].Seed fatty acids contain elaeostearic,linoleic,oleic and saturated acids[25].

6.1.Cucurbitacin B

Cucurbitacins are a group tetracyclic triterpenoids mainly found in the plants of Cucurbitaceae.So far 17 cucurbitacins have been identified in different cucurbits[77].Cucurbitacin B has been isolated from the fruits ofT.dioica[75].This compound has been extensively studied and found effective in different types of cancers including breast cancer,ovarian cancer,lung cancer,prostate cancer,osteosarcoma,and melanoma,[78–86]and in sepsis-induced acute lung injury[87].Besides,different molecular mechanisms have been identified in different types of cancer cell lines that contribute to its anticancer activity[77,79,80,83–85,88–94].In a recent study,low-dose cucurbitacin B and low-dose methotrexate exhibited a synergistic anticancer effect in the treatment of human osteosarcoma[78].Synergism in activity has also been observed with cucurbitacin B and curcumin in multidrug resistance human hepatoma cells[95].It also exhibited chemosensitizing property in cisplatin and paclitaxel-resistant ovarian cancer[86,96].

6.2.Trichosanthin

Trichosanthin is a protein known for its abortifacient,immunosuppressant and antitumor activity[97].It is a 27-kDa protein having a single chain of 247 amino acids residues[61].It was primarily isolated fromTrichosanthes kirilowiiroot[97]and it has been reported in the roots ofTrichosanthes dioica[25].This ribosome inactivating protein has already shown antitumor,anti-HIV-1,anti-HSV-1 and immunoregulatory properties[98–100].It has been studied in numerous types of cancer cell lines and found effective in choriocarcinoma,cervical cancer,lymphoma,hepatoma,colon carcinoma,stomach cancer,lung cancer,breast cancer,prostate cancer,and melanoma[62,101,102].Induction of apoptosis(e.g.,by activating caspase-3,caspase-8 pathway,increasing reactive oxygen species,arrest of cell cycle G1 phase),calcium level increase in cytosol,decrease in cyclic adenosine monophosphate as well as protein kinase C and inhibition of telomerase activity is thought to be involved in its anticancer activity observed in different cell lines[61,101,103,104].

6.3. α-Amyrin and β-amyrin

These compounds are pentacyclic triterpene which has been reported in the roots ofT.Dioica[73].α-amyrin containing plant extracts have shown antimicrobial and antifungal activity[105].Extracts containingα-amyrin and/or β-amyrin also exhibited anti-inflammatory activity[105,106].β-amyrin also exhibited anti-lipoxygenase activity[107].

6.4.Euphol

The triterpenoid alcohol euphol was first isolated from the dried latex ofEuphorbia tirucalli[108].Later it has been reported in other plants includingT.Dioicaroot[73].It exhibits a number of biological activities such as hypotensive[109],anticolitis[110],anti-inflammatory[111]and anti-viral activities[112].Euphol also showed spinal and supraspinal antinociception by inhibiting inflammatory mediators and largely by interacting with the cannabinoid system[113–115].In more recent studies,the anticancer activity of euphol has been reported in T47D breast cancer and human gastric cancer cell lines.The effect was due to the arrest of cell cycle and ERK1/2-mediated apoptosis[116,117].

6.5.Taraxerol

Akihisa,et al.[73]isolated taraxerol from the roots ofT.dioica.Taraxerol,an oleanane triterpenes,has been isolated from different types of plants including common dandelionTaraxacum of ficinaleand different mangrove plants[118–120].Taraxerol possesses antitumor,anti-inflammatory,antimicrobial and anti-snake venom activity[119,121].It has shown activity against sarcoma 180 cell line and inhibited spontaneous mammary tumors in mice[121].Taraxerol also induces cell cycle arrest and promote apoptosis in human gastric epithelial cell line AGS cells[122].Besides these two mechanisms induction of autophagy as well as cell migration inhibition are also involved it’s(taraxerol acetate)anticancer activity in U87human glioblas-toma cell line[123].In HeLa cell line the apoptosis is mediated by the mitochondrial pathway[124].It also induces apoptosis,inhibits cyclo-oxygenase and acetylcholinesterase and reverses insulin resistance in 3T3L1 adipocytes[119,121].

6.6.Lupeol

It is mainly a dietary triterpene found in different vegetables and fruits as well as in numerous medicinal plants[125].In the last two decades,lupeol has been extensively studied for different biological activities and as a result,its efficacy in diverse human ailments such as inflammation,hepatic toxicity,arthritis,renal damage,diabetes,cardiovascular ailments,microbial infections and cancer has been reported[125–127].

6.7.Karounidiol

This compound is a multi florane-type triterpenoid that has been isolated from the seeds ofT.dioicaand some otherTrichosanthesspecies.Karounidiol was found to inhibit tumor promotion induced by 12-O-Tetradecanoylphorbol-13-acetate in mice[128].Akihisa,et al.[129]also reported the cytotoxic potency of this compound against human renal cancer cell lines.

6.8.Betulin

Betulin(Lup-20(29)-ene-3β,28-diol)is a naturally occurring triterpene of lupane structure mainly found in the bark birch tree but it has been reported in at least twenty different plant species of the different family[130].Akihisa,et al.[74]isolated betulin from the seeds ofT.dioica.Antiseptic and antirachitic properties of betulin were the first bioactivities that were reported.Later investigations on extracts containing betulin confirmed numerous properties of betulin including cholesterol lowering,anti-inflammatory,hepatoprotective,wound healing,antitumor and choleretic properties[130–132].The antitumor potential of betulin has been studied in different types of cell lines.Though it has been reported less active in different types of human melanoma cell lines,it has been found effective in colorectal,prostrate,breast,lung and other cancer cell lines[133,134].The potent antitumor activity of betulin is due to the apoptosis of cancer cells by mitochondrial,caspase-activated and other cellular protein-mediated pathways[134].A recent work also reports its chondroprotective activity in rat[135].

6.9.24-Methylcholesterol and 28-isofucosterol

Though a number of sterols have been reported in the unsaponifiable lipids from the root ofT.dioica,only two of them,namely 24-methylcholesterol and 28-isofucosterol,were found bioactive.24-Methylcholesterol and 28-isofucosterol isolated from the soft coral extracts have shown antibacterial activity againstBacillusspp.andOchrobactrum pseudogrignonesein disc-diffusion assay in a similar pattern of Cu2O used as positive control[136].This activity has shown the potential of these sterols as an antifouling agent but their activities against human pathogenic organism are yet to be explored.

7.Conclusions

T.dioicais of considerable importance as it possesses a wide spectrum of pharmacological properties such as antihyperglycemic,antihyperlipidemic,antitumor,cytotoxic,arsenic poisoning amelioration,anti-inflammatory,antidiarrhoeal activities etc.These properties are associated with diverse groups of chemical constituents including peptides(trichosanthin and lectin),triterpenes(cucurbitacin B,euphol,α-amyrin,β-amyrin,lupeol,taraxerol,betulin and karounidiol),sterols(24-methylcholesterol,24-methylenecholesterol,24-ethylcholesterol,28-isofucosterol,avenasterol)etc.Although pharmacological properties of extracts,triterpene rich fraction or compounds isolated fromT.dioicaare substantiated by theinvitroandin vivostudies in different animal models,the mechanisms of these activities are yet to be addressed.An emphasis should be given on further mechanistic studies using animal models and cell cultures.Besides,the only human trial reporting its therapeutic potential dates back almost three decades ago and in a small group of patients[42].Adequate well-defined clinical trials with large patient groups are required to substantiate the significant role of this edible species in health care.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential Conflict of interest.

Author contributions

MK,SA and MZI contributed equally in preparing the manuscript.

Acknowledgement

No funding was received for this work from any organization.