International Journal of Nutrition, Pharmacology, Neurological Diseases

REVIEW ARTICLE
Year
: 2011  |  Volume : 1  |  Issue : 2  |  Page : 90--96

Colocasia esculenta: A potent indigenous plant


Rakesh Prajapati, Manisha Kalariya, Rahul Umbarkar, Sachin Parmar, Navin Sheth 
 Department of Pharmaceutical Sciences, Saurashtra University, Rajkot, Gujarat, India

Correspondence Address:
Rakesh Prajapati
Department of Pharmaceutical Sciences, Saurashtra University, Rajkot - 360 005, Gujarat
India

Abstract

Colocasia esculenta (CE) Linn. (Family: Araceae) is an annual herbaceous plant with a long history of usage in traditional medicine in several countries across the world, especially in the tropical and subtropical regions. The herb has been known since ancient times for its curative properties and has been utilized for treatment of various ailments such as asthma, arthritis, diarrhea, internal hemorrhage, neurological disorders, and skin disorders. The juice of CE corm is widely used for treatment of body ache and baldness. A wide range of chemical compounds including flavonoids, β-sitosterol, and steroids have been isolated from this species. Extracts from this plant have been found to possess various pharmacological activities. This contribution provides a comprehensive review of its ethnomedical uses, chemical constituents, and the pharmacological profile as a medicinal plant. Particular attention has been given to analgesic, anti-inflammatory, anti-cancer, and hypolipidemic effects presented in this review in order to evaluate the potential use of this plant in pharmaceuticals.



How to cite this article:
Prajapati R, Kalariya M, Umbarkar R, Parmar S, Sheth N. Colocasia esculenta: A potent indigenous plant.Int J Nutr Pharmacol Neurol Dis 2011;1:90-96


How to cite this URL:
Prajapati R, Kalariya M, Umbarkar R, Parmar S, Sheth N. Colocasia esculenta: A potent indigenous plant. Int J Nutr Pharmacol Neurol Dis [serial online] 2011 [cited 2019 Jun 17 ];1:90-96
Available from: http://www.ijnpnd.com/text.asp?2011/1/2/90/84188


Full Text

 Introduction



It is a well-known fact that traditional systems of medicines have always played important role in meeting the global healthcare needs. They are continuing to do so at present and shall play major role in future as well. The system of medicines that are considered to be Indian in origin or the systems of medicine, which came to India from other countries and assimilated in Indian culture are known as Indian Systems of Medicine. India has the unique distinction of having six recognized systems of medicine in this category. They are Ayurveda, Siddha, Unani and Yoga, Naturopathy and Homoeopathy. [1]

Among them, Ayurveda has been practiced for thousands of years. Considerable research on pharmacognosy, chemistry, pharmacology, and clinical therapeutics has been carried out on Ayurvedic medicinal plants. Natural products, including plants, animals, and minerals have been the basis of treatment of human diseases. The current accepted modern medicine or allopathy has gradually developed over the years by scientific and observational efforts of scientists. However, the basis of its development remains rooted in traditional medicine and therapies. [2]

Plants have played a significant role in maintaining human health and improving quality of human life since long and have served humans well as valuable components of medicines, seasoning, beverages, cosmetics, and dyes. The popularity of herbal medicine in recent times is based on the premise that plants contain natural substances that can promote health and alleviate illness. Therefore, the focus on plant research has increased all over the world and a large body of evidence show immense potential of medicinal plants used in various traditional system. There are many herbs that are predominantly used to treat cardiovascular, liver, central nervous system (CNS), digestive, and metabolic disorders. Given their potential to produce significant therapeutic effect, they can be useful as drug or supplement in the treatment or management of various diseases. Herbal drugs or medicinal plants, and their extracts and isolated compounds have demonstrated a wide spectrum of biological activities. Ethnopharmacological studies on such herbs or medicinally imported plants continue to interest investigators throughout the world. [3]

Selection of scientific and systematic approach for the biological evaluation of plant products based on their use in the traditional systems of medicine forms the basis for an ideal approach in the development of new drugs from plants. One such plant is Colocasia esculenta Linn, commonly known as taro (English); aravi (Hindi) and alupam (Sanskrit). It is a tall and perennial herbaceous plant growing throughout India.

Plant profile

Colocasia esculenta Linn. (Family: Araceae) [Figure 1] is also known as Arum esculentum L. and Colocasia antiquorum Schott. [4] It is commonly called as taro (English); alavi, patarveliya (Gujarati); arvi, kachalu (Hindi); alu (Marathi); alupam, alukam (Sanskrit); and sempu (Tamil). Geographically, it occurs throughout India and is cultivated worldwide. [5],[6]{Figure 1}

Geographical distribution

It is a wild plant and cultivated throughout the hotter parts of India and Ceylon. It is cultivated in all hot countries.

Habitat [7]

For taroleaf production, magnesium was found to have a significantly favorable effect. Under the agroclimatic conditions of Kerala, a spacing of 60Χ45 cm, and the use of green leaf mulch, significantly increased the yield, but did not affect the quality aspect of the cormels, such as starch and oxalate content. Use of leaf mulch increased the protein content of the cormels. The growth and yield of taro were found to increase by using Dadap (Erythrina spp.) and Panicum maximum Linn. as soil mulches, the former being more effective than the latter.

Botanical description

Parts used: Leaves and corms [Figure 2]{Figure 2}

Morphology [8]



Colocasia esculenta Linn. is a tall herb [Figure 1], tuberous or with a stout short caudex, flowering and leafing together.Leaves are simple, with a stout petiole, lamina peltate, ovate-cordate or sagittate-cordate. Spadix shorter than the petiole and much shorter than the spathe, appendix much shorter than the inflorescence.Petiole erect, up to 1.2-m long, rarely longer with a triangular sinus cut one-third to half way to petiole, with a dull, not polished surface above, paler or colored beneath, but rarely glaucous.Peduncle shorter than the petiole, spathe pale yellow, 15- to 35-cm long; tube greenish, oblong; lamina narrowly lanceolate, acuminate, convolute, never widely open, and curved slightly backwards in flower.Female inflorescence short, male inflorescence long, cylindrical, usually interposed neuters between the two. Appendix erect, elongate-conical or fusiform, subulate or abbreviate. Male flowers 3-6 androus.Female flowers 3-4 gynous; ovary ovoid or oblong, one-locular; ovules several or many, biseriate; style 0 short in the beginning, later on 0; stigma depressed-capitate, very shortly 3-5 sulcate.Berries obconic or oblong, many seeded. Seeds oblong, sulcate. Albumen copious; embryo axile.Stem above ground 0, or slightly swollen at the base of the leaf-sheaths, arising from a hard tapering rhizome or in cultivated forms a tuberous rhizome suckers and stolons sometimes present.Spadix much shorter than the spathe rather than slender. Female inflorescence as long as the sterile male inflorescence. Appendix much shorter than the inflorescence, style very short; stigma discoid.

Microscopical features of C. esculanta leaf [9]

Upper Epidermis

Epidermis is made up of single layer of spherical to polygonal cells with straight to slightly beaded anticlinal walls, wavy in shape. Chlorophyll is present in epidermal cells. The outer surface is cutinized.

Mesophyll

It shows dorsiventral arrangement and mesophyll is differentiated into palisade and spongy parenchyma. Palisade cells filled with chlorophyll and phenolic compounds.

Spongy parenchyma

The leaf is monocot, so it shows presence of vacuoles. It is made up of parenchymatous cells with varying size and shape, which measures about 7-9 cells in thickness, with intermittently interspersed vascular elements. A majority of cells are filled with compound-type starch grains. Starch grains are simple, spherical with centric helium and less prominent striations.

Lower epidermis

Epidermis is made up of single layer of polygonal cells with straight to slightly beaded anticlinal walls. It shows the presence of paracytic type of stomata and papillae.

Conducting tissue system

Each vascular bundle is simple and surrounded by a single layer of parenchymatous bundle, while larger vascular bundles are surrounded by sclerenchymatous bundle sheath. This extends up to the upper or lower or both epidermis.

Traditional uses [8]



The pressed juice of the petiole is stypic, and may be used to arrest arterial hemorrhage.It is sometimes used in ear ache and otorrhoea, and also as stimulant and rubefacient and also in internal hemorrhages.Leaf juice is stimulant, expectorant, astringent, appetizer, and otalgia.The juice expressed from the leaf stalks with salt is used as an absorbent in cases of inflamed glands and buboes.Cooked vegetable contains mucilage and found to be an effective nervine tonic.Decoction of the peel is given as a folk medicine to cure diarrhea.Increases body weight, prevents excessive secretion of sputum in asthmatic individuals.Juice of the corm is used in cases of alopecia.Internally, it acts as a laxative, demulcent, anodyne, galactagogue and is used in cases of piles and congestion of the portal system; also used as an antidote to the stings of wasps and other insects.Corm is used by people of the Munda tribe as a remedy for body ache.

Phytochemistry

Mainly leaves contain calcium oxalate, fibers, minerals (calcium phosphorus, etc.), and starch, vitamin A, B, C, etc. [5] Phytochemically, these also contain flavones, apigenin [Figure 3], luteolin [Figure 4], and anthocyanins [Figure 5]. [10]{Figure 3}{Figure 4}{Figure 5}

CE tubers contain globulins accounting for 80% of the total tuber proteins, belonging to two unrelated globulin families. [11] The total amino acids recorded in the tubers are in the range of 1,380-2,397 mg/100 g. The lysine concentration was relatively low. [10]

The starch content of the flour varies from 73-76% and the starch yields are in the range of 51-58%. The nitrogen content in the flours varies from 0.33-1.35%. The starch contains 0.23-0.52% lipid and 0.017-0.025% phosphorus in the form of phosphate monoester derivatives. [11]

Corm contains starch, mucilage, dihydroxysterols, fat, calcium oxalate, vitamin B, iron, etc. [5] Besides starch, the tubers contain natural polysaccharide with 56% neutral sugars and 40% anionic components. Steamed corms contain 30% starch and 3% sugar. [10] From the tubers, two dihydroxysterols, 14α-methyl-5α-cholesta-9, 24-diene-3b, 7α-diol and 14α-methyl-24-methylene-5α-cholesta-9, 24-diene-3α, 7 α-diol, besides b-sitosterol [Figure 6] and stigmasterol, nonacosane and cyanidin 3-glucoside [Figure 7] have been isolated. In addition, five novel aliphatic compounds tetracos-20-en-1, 18-diol; 25-methyl triacont-10-one; octacos-10-en-1, 12-diol; pentatriacont-1, 7-dien-12-ol and 25-methyl-tritriacont-2-en-1, 9, 11-triol, along with nonacosane and cyanidin 3-glucoside have been reported. An antifungal compound, 9, 12, 13-trihydroxy-(E)-10-octadecenoic acid, and two enzymes, lipoxygenase and lipid hydroperoxide-converting enzyme, which are responsible for the production of antifungal lipid peroxides, were detected in taro tubers infected by Ceratocystis fimbriata0.[7]{Figure 6}{Figure 7}

Phytochemical investigations

Flavonoids

Iwashina et al. carried out isolation and identification of the flavonoids in the leaves of C. esculenta plant. The flavonoids were identified by UV spectral analysis. They isolated eight flavonoids viz. orientin, isoorientin, isovitexin, vicenin-2, orientin 7-O-glucoside, isovitexin 3'-O-glucoside, vitexin X" -O-glucoside, luteolin 7-O-glucoside [12] [Table 1] and [Figure 8].{Table 1}{Figure 8}

Further, Nakayama et al. investigated anthocyanin composition in the plant. In his study, anthocyanins were extracted with 50% methanol, further isolated by adsorption on insoluble polyvinylpyrrolidone, and purified by thin layer chromatography. The pigments were identified by chromatographic and spectrophotometric methods as pelargonidin 3-glucoside, cyanidin 3-rhamnoside, and cyanidin 3-glucoside. Levels of anthocyanins were highest in the skin of the corm, 16.0 mg%, with equal amounts, 3.29 mg%, in both corm and petiole. Anthocyanogens ere also present in the plant. [13]

Oxalate content

Huang et al. measured oxalate contents in Colocasia corms, using strong anion-exchange column chromatography. In the study, the column was developed with a mobile phase of 3 mM phthalic acid with its pH adjusted to 3.5 using lithium hydroxide. The flow rate was adjusted at 1.0 ml/min. The system was compatible with a conductivity detector. Total oxalates and soluble oxalates were measured in 1 N HCl and water extracts, respectively. Insoluble oxalate contents were the differences between them by calculation. In nine taro cultivars, total oxalate contents were in the range of 33-156 mg/100 g of fresh weight and soluble oxalate contents in the range of 19-87 mg/100 g of fresh weight. Insoluble oxalate contents were calculated to be 29.35-73.97% of the total oxalate contents in tested plant corms. [14]

Ethnopharmacology

Bioactivity

Cooked vegetable contains mucilage and is an effective nervine tonic. Leaf juice is a stimulant, expectorant, astringent, appetizer, and otalgia. The juice expressed from the leaf stalks with salt is used as an absorbent in cases of inflamed glands and buboes. Decoction of the peel is given as a folk medicine to cure diarrhea. The juice of the corm is used in cases of alopecia. Internally, it acts as a laxative, demulcent, anodyne, galactagogue and is used in cases of piles and congestion of the portal system, as well as an antidote to the stings of wasps and other insects.

Pharmacological reports

Hypoglycemic property

Grindley et al. screened the anti-diabetic action of the CE plant. As part of the study, they investigated carbohydrate digestion and intestinal ATPases in streptozotocin-induced diabetic rats fed extract of the plant. In the study, streptozotocin-induced diabetic rats were maintained for four weeks on the plant extract or commercial linamarin. Rats fed commercial linamarin had significantly lower blood glucose level compared to the diabetic rats fed normal diet. Feeding of commercial linamarin to diabetic rats significantly decreased the activity of intestinal amylase compared to that on normal rats. Plant extract or commercial linamarin significantly increased the activities of intestinal disaccharidases compared to diabetic rats fed normal diet. Na + /K + ATPase activity in the lower segment of the intestine was significantly reduced in diabetic rats compared to normal rats. In the upper segment of the intestine, plant extract or commercial linamarin supplementation increased the activity of the enzyme above the normal level. Those observations reveal that the plant possesses hypoglycemic activity and that may be due to its cyanoglucoside content. [15]

Antifungal activity

Yang et al. evaluated the antifungal activity of taro, along with molecular cloning and recombinant gene expression studies. A cDNA clone, designated CeCPI, encoding a novel phytocystatin was isolated from taro corms using both degenerated primers/reverse transcription-polymerase chain reaction (RT-PCR) amplification and 5′-/3′-Rapid amplification of cDNA ends (RACE) extension. Sequence analysis revealed that CeCPI is phylogenetically closely related to Eudicots rather than to Monocots, despite taro belonging to Monocot. Recombinant GST-CeCPI fusion protein was over-expressed in Escherichia coli and its inhibitory activity against papain was identified on gelatin/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). These results confirmed that recombinant CeCPI protein exhibited strong cysteine protease inhibitory activity. Thus, the investigation clearly revealed a toxic effect of the plant on the mycelium growth of phytopathogenic fungi. [16]

Anti-cancer action

Brown et al. evaluated in vitro anti-cancer effect of the plant on colonic adenocarcinoma cells. In the study, soluble extracts of plant were incubated at 100 mg/ml in vitro for antiproliferative activity against the rat YYT colon cancer cell line. 3H-thymidine incorporation studies were conducted to demonstrate that the plant inhibited the proliferation of these cancer cells in a dose-dependent manner. The greatest suppression of YYT colon cancer growth occurred when 25% concentration was used. When plant extract was incubated with the YYT cells after 2 days, the YYT cells underwent apoptotic changes. The plant enhanced the proliferation of normal mouse splenocyte control cells, suggesting that the plant is not simply toxic to all cells but even has a positive immunostimulatory role. Thus, the plant showed the anticancer action by two distinct mechanisms: one, by inducing apoptosis within colon cancer cells; and the second, by non-specifically activating lymphocytes, which, in turn, can lyse cancerous cells. [17]

Hypolipidemic effect

Sakano et al. tested ethanolic extract of the taro plant (CE) along with other 130 vegetables, for inhibition of human lanosterol synthase (hOSC) in order to find the compounds to suppress cholesterol biosynthesis. During the study, 12 samples showed significant inhibition, while highest inhibition (55% inhibition at 300 mg/ml) was found with taro. Moreover, examination of activity variation among eight taro cultivars indicated that "Aichi-wase" and "Yatsugashira" had the most potent activity for hOSC inhibition. In order to identify the active constituent of taro, ethanolic extracts of "Aichi-wase" were partitioned with hexane and aqueous methanol and fractionated by silica gel column chromatography. Inhibitory activity was concentrated in two major active fractions. Further purification of these fractions by preparative high performance liquid chromatography (HPLC) yielded three monogalactosyl diacylglycerols and five digalactosyl diacylglycerols as active compounds that showed 28-67% inhibitory activities at the concentration of 300 mg/ml. [18]

Moreover, Boban et al. studied the effects of mucilage, isolated from taro (CE), fenugreek (Trigonella foenumgraecum), and Dioscorea esculenta on metabolism of lipids and lipoproteins by using experimental animal models. The mucilages identified were a galactomannan from fenugreek seeds; a glucomannan from D. esculenta tubers, and an arabinogalactan from CE tubers. Rats were fed these mucilages at a dose of 3 mg/100 g body weight per day for 8 weeks. All these mucilages decreased the lipid levels both in serum and tissues. Among these mucilages, glucomannan showed the most hypolipidemic effect followed by galactomannan and arabinogalactan. Further, hepatocytes were isolated from the livers of mucilage-fed rats. There was a decrease in the synthesis and secretion of apoB-containing lipoproteins, mainly very-low-density lipoprotein (VLDL), by hepatocytes isolated from mucilage-fed rats when compared to control (P<0.05). Further, this was confirmed by pulse-chase analysis. Among different mucilages, mannose-rich glucomannan showed the prominent effect, followed by galactomannan, and mannose-free arabinogalactan showed minimal effect. The study results suggested that the hypolipidemic effect of dietary fiber from the plant involved a decrease in hepatic production of VLDL and that it varied with the nature of the fiber. [19]

Anti-inflammatory activity

Shah et al. investigated anti-inflammatory activity of the ethanolic extract of the leaves of CE in Wistar rats using the carrageenan-induced left hind paw edema, carrageenan-induced pleurisy, and cotton pellet-induced granuloma model. The ethanolic extract (100 mg/kg, p.o.) inhibited carrageenan-induced rat paw edema. It inhibited leukocyte migration, reduced the pleural exudates, and reduced the granuloma weight in the cotton pellet granuloma method. The results indicated that the ethanolic extract produced significant (P<0.05) anti-inflammatory activity when compared with the standard and untreated control. [20]

Nervine tonic

Manisha et al. evaluated the neuropharmacological activities of hydroalcoholic extract of leaves of CE using several experimental models. In the study, adult Wistar albino rats were subjected to behavior despair and elevated plus maze (EPM) tests. Thiopental-induced sedation and rotarod tests were conducted on Swiss albino mice. The effects of the plant extract on anxiety, depression, thiopental-induced sleeping time, and rotarod performance were evaluated. The anxiolytic activity of extract (100, 200, and 400 mg/kg) per os (p.o.) was characterized by increased time spent and number of entries in open arms in the EPM paradigm as compared to control group (P<0.001). The extract (100, 200, and 400 mg/kg, p.o.) showed a dose-dependent significant reduction in the duration of immobility (P<0.01) in the behavior despair test. The plant extract at doses 50 and 100 mg/kg, i.p. was found to produce a significant reduction in motor coordination (P<0.001) and prolongation of thiopental-induced sleeping time (P<0.001). Thus, results of the study showed that the plant possesses various neuropharmacological activities such as anti-depressant, anxiolytic, sedative, and smooth muscle relaxant activity. [21]

 Discussion and Conclusions



Medicinal plants are local heritage with the global importance. The world is endowed with a rich wealth of medicinal plants. Medicinal plants play an important role in the lives of rural people, particularly in remote parts of developing countries with few health facilities. The present review revealed that CE is utilized for the treatment of some common diseases. In the present review, we have congregated information pertaining to botanical, phytochemical, and pharmacological studies. The plant has been studied for various pharmacological activities such as analgesic, anti-inflammatory, anti-cancer, anti-diarrheal, astringent, nervine tonic, and hypolipidemic activity. Moreover, chemically, the plant contains various biologically active phytoconstituents such as flavonoids, sterols, glycosides, and other micronutrients. Therefore, it is necessary to exploit it to its maximum potential in the medicinal and pharmaceutical field.

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