INTRODUCTION:

There has been tremendous growth in the area of herbal medicines in last few decades^{1, 2,3}. Day by day, the herbal medicines are getting more attention in developing and developed countries due to their less side effects and its natural plant origin^4,5,6. Plants have played an important role in maintaining human health and improving quality of human life^7,8,9. Colocasia esculenta Linn. is one of the widely available plant all over the globe. Colocasia esculenta Linn. is commonly known as Arum esculentum L. and Colocasia antiquorum Schott. It is commonly called as taro¹⁰. Colocasia esculenta Linn. is herbaceous, tuberous plant in nature. It has robust short caudex, flowering together.

It is also commonly recognized as ‘elephant’s ear’ due to its leaves that are shaped likea large ear. Taro leaves and taro stem is used as vegetable in Indian traditional food system^{11, 12}.

Plant Profile^12,13:

Colocasia esculenta

Fig. 1: Leaves of C. esculenta

Fig. 2: Corms of C. esculenta

Taxonomy:

Scientific classification⁶

Kingdom: Plantae (Plants)

Subkingdom: Tracheobionta (Vascular plants)

Super division: Spermatophytes (Seed plants)

Division: Mangoliophyta (Flowering Plants)

Class: Liliopsida (Monocotyledons)

Subclass: Arecidae

Order: Arecidae

Family: Araceae (Arum family)

Genus: Colocasia Schott (colocasia)

Species: Colocasia esculenta (L.) Schott (Coco yam)

Synonym: Alocasia dussil Dammer, Alocasia illustris W. Bull

Vernacular Names:

Table 1: Different vernacular names of C. esculenta in India¹⁴

Sr. No.	Language	Name
1	English	Taro
2	Hindi	Aravi
3	Sanskrit	Alupam
5	Marathi	Alu

Table 2: Different vernacular names of C. esculenta in the various countries other than India¹⁵

Sr. No.	Country	Name
1	Republic of South Africa	Dmmbhe
2	Ghana	Cocoyam
3	Fiji	Ndalo
4	Tahiti	Taro
5	Samoa	Talo

Nutritional Information:

The corms of taro are rich in proteins, carbohydrates, Vitamins, minerals andconsidered to have some important values in daily human routine. Taro contains carbohydrate and about 11% protein more than potatoes, it also contains 85-87% starch and other nutrients like Vitamin C, thiamine, riboflavin and niacin¹⁶.

Table 3: Approximate content of nutrition in taro

Sr. No.	Nutrition	Content
Sr. No.	Nutrition	Corms¹⁷	Leaves^18,19
1	Carbohydrate (%)	13-29	12.2
2	Protein (%)	1.4-3	4.4
3	Crude fibre (%)	0.6-1.18	3.4
4	Thiamine (mg/100g)	0.18	0.1
5	Niacin (mg/100g)	0.9	2
6	Vitamin C (mg/100g)	7-9	142
7	Riboflavin (mg/100g)	0.04	0.33

GEOGRAPHICAL DISTRIBUTION:

The overall production of Colocasia esculenta Linn. is assessed globally at 11.8million tons per annum and most of the developing countries produces taro crop^{20,21, 22}. The global production of taro is evaluated at 10.2 million metric tons. In Ghana and Papua New Guinea, taro production is assessed at 1.3 and 0.3 million metric tons respectively. In Nigeria, taro production is very high and is evaluated at 3.3 million metric tons²³.

BOTANICAL DESCRIPTION:

Colocasia esculenta Linn. is herbaceous, tuberous plant in nature. It has robust short caudex, flowering together. The leaves of taro are generally heart shaped. The stem of taro plant is orange, red-black in colour. Roots are adventitious and shallow. This root system facilitates production of fine starch from the corm²⁴. The elongated leaves which are 1-2m in height, 23 inches thick &30–90 cm long called as ‘elephant head’^{25, 26}. The height of taro plant is always up to 2m. The cylindrical corms have diameter about 30cm²⁷.

General description²⁸

Type: Bulb

Height: 3-6 feet

Spread: 3-6 feet

Bloom time: July to August

Bloom colour: White

Bloom description: Yellowish-white

Flowers: Showy Flowers

Leaves: Green

Phytochemistry:

The two important therapeutically active chemical constituentsare present in taro leaf extract namely flavonoids and triterpenoids.

Flavonoids

UV spectral analysis was done for identification of flavonoids in the leaves of C. esculenta plant. Total eight flavonoids was found in the Colocasia leaf extract that areOrientin, Isoorientin, Isovitexin, Vicenin-2, Orientin7-Oglucoside, Isovitexin 3’-O-glucoside, Vitexin X’’-Oglucoside and Leteolin 7O-glucoside³¹.

Anthocyanins:

Chromatographic and spectrophotometric methods were used for isolation and identification of anthocyanins in taro leaf extract. Anthocyanins present in the Colocasia leaf extract are Cyanidin-3-glucoside, Pelargonidin-3-glucoside and Cyanidin-3-rhamnoside^33,
34. The anthocyanins are also present in the corms of C. esculenta plant in very high amount³⁵.

Oxalate content:

The total oxalate contents was in the range of 33-156mg/100 g of fresh weight in the corms of C. esculenta³⁶.

Starch:

The corms of taro contains about 70–80% (dry weight basis) starch with small Granules³⁷.

Fig. 3: Structures of Flavonoids in C. esculenta³²:(a) Orientin (b) Isoorientin

Pharmacological Activities:

· Antidiabetic/Hypoglycaemic

· Antimicrobial

· Anti-lipid per oxidative

· Antifungal

· Anti-inflammatory

· Nervine tonic

· Hepatoprotective/Antihepatotoxic

· Anticancer

Hypoglycaemic activity:

The anti-diabetic activity of ethanolic extract of C. esculenta leaves was estimated on blood glucose level and on body weight by using alloxan induced diabetic rat model. Preliminary phytochemical investigation showed that the alkaloids, flavonoids, saponins and tannins are present in the ethanol extract³⁸. The major constituent in the ethanol extract was flavonoids. Hpoglycaemic activity was reported due to alkaloids, flavonoids, saponins and tannins³⁹.

Antimicrobial activity:

Aqueous extract of Colocasia esculenta (AECE) leaves was evaluated for in-vitro antimicrobial activity. The in-vitro antimicrobial activity was estimated against gram positive bacterial strains i.e. Bacillus subtillis, Streptococcus mutans; gram negative bacterial strains i.e. Klebsiella pneumoniae, Pseudomonas fragi, Escherichia coli and fungal strains i.e. Aspergillus niger Candida albicans by using agar well diffusion^40,41.

Anti-lipid per oxidative activity:

The anti-lipid per oxidative activity of Colocasia esculenta leaf was determined on rat liver cells by usingin vitro rat liver slice model. The liver slices was incubated with cytotoxic concentrations of CCl4 and acetaminophen (Paracetamol). Co-incubation of liver slices with the hepatotoxins and taro leaf juice was studied to evaluate the potency of Colocasia esculentaleaf juice in scavenging the free radicals which was formed by the metabolism of CCl4 and acetaminophen (Paracetamol)^42,43,44.

Antifungal activity:

The Colocasia esculenta plant was evaluated for antifungal activity, along with molecular cloning and recombinant gene expression studies. A cDNA clone CeCPI (encoding a phytocystatin) was isolated from corms of Colocasia esculenta by using degenerated primers/ reverse transcription-polymerase chain reaction (RTPCR) and 5′-/3′-Rapid amplify cation of cDNA ends (RACE) extension. This study revealed that recombinant CeCPI protein showed cysteine protease inhibitory activity^45,46.

Anti-inflammatory activity:

The ethanolic leaf extract of Colocasia esculenta Linn.plant was evaluated for anti-inflammatory activity in Wistar rats. The anti-inflammatory activity was studied using the carrageenan-induced left hind paw oedema, cotton pellet induced granuloma model and carrageenan induced pleurisy^{47, 48}.

Nervine tonic:

The hydro alcoholic leaf extract of Colocasia esculenta plant was evaluated for neuro-pharmacological activities in adult Wistar albino rats. For the estimation of neuro-pharmacological activities, wistar albino rats was subjected to elevated plus maze (EPM) tests. Thus, the study showed that the Colocasia esculenta planthas various neuro-pharmacological activities such as antidepressant, anxiolytic, sedative, and smooth muscle relaxant activity⁴⁹.

Hepatoprotective activity:

The hepatoprotective activity of aqueous extract of Colocasia esculenta leaves was studied against thioacetamide (TAA) induced liver injury in rats. TAA is widely used to induce hepatotoxicity in various animal models^{50, 51}. The liver cells containsdifferent enzymes, which are essential for various metabolic processes. The intracellular liver-specific enzymes areaspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP)⁵². TAA-induced hepatotoxicity was increased ALP, ALT, AST and the aqueous leaf extract of Colocasia esculenta reduced ALT, AST, and ALP levels⁵³.

Anticancer activity:

The anticancer activity of Colocasia esculenta plant was studied againstrat YYT colon cancer cell line. The 3H-thymidine was incorporated to determine that the plant inhibited the multiplication of YYT colon cancer cells of rat⁵⁴.

CONCLUSION:

It is quite evident from this review that colocasia esculenta is an important medicinal plant. It contains a number of phytoconstituents, which are the key factors in the medicinal value of this plant. Almost all parts of this plant such as leaf, fruit, seed, and root are used to cure a variety of diseases. The present review summarizes some important pharmacological studies on colocasia esculenta and phytochemical investigations and isolated principles from them. Thorough screening of literature available on colocasia esculenta depicted the fact that it is a popular remedy among the various ethnic groups, Vaidyas, Hakims and Ayurvedic practitioners for cure of variety of ailments. A systemic research and development work should be undertaken for the development of products for their better economic and therapeutic utilization.

ACKNOWLEDGMENT:

The authors would like to acknowledge Dr. Ashwini R. Madgulkar, Principal, AISSMS College of Pharmacy, Pune, for her encouragement and guidance.

CONFLICTS OF INTEREST:

No conflict of interest was declared by the authors. The authors alone are responsible for the content and writing of the paper.

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Received on 06.12.2022 Modified on 30.03.2023

Res. J. Pharmacology and Pharmacodynamics.2023;15(3):144-148.

DOI: 10.52711/2321-5836.2023.00026

Sr. No.	Component		Characteristic
1	Epidermis	Upper Epidermis	It is single layered consisting spherical to polygonal cells with straight to slightly beaded anticlinal walls. Chlorophyll is present in upper epidermal cells. The outer surface of upper epidermis is cutinized.
		Lower epidermis	Lower epidermis is single layered consisting spherical to polygonal cells with straight to slightly beaded anticlinal walls. Parasitic stomata and papillae are present in lower epidermis.
2	Mesophyll		Mesophyll has dorsiventral arrangement and it is characterised into palisade and spongy parenchyma. Chlorophyll and some phenolic compounds are present in palisade cells.
3	Spongy parenchyma		The leaf is monocot, so vacuoles are present. It is made up of parenchymatous cellswhich measures about 7-9 cells in thickness. Compound-type starch grains are present in a major part of spongy parenchyma cells. These starch grains are simple, spherical with centric helium.