Centella asiatica has been employed as a medicinal plant in India and south- east Asia since prehistoric times. The name hydrocotyle is derived from the Greek words for 'water' and 'cup', to describe the habitat, water, and the appearance of the leaves, cup-shaped.
Centella asiatica is the most ubiquitous species of Centella and is found in India, Sri Lanka, south-east Asia, China, Madagascar, South Africa, south-eastern USA, Mexico, Venezuela and Columbia. It grows in moist habitats at altitudes up to 2500 m.
A perennial. slender, herbaceous, creeper plant (Plate 18) flowering between August and September. The plant has a smell reminiscent of tobacco and a mildly bitter taste. The leaves are glabrous, kidney shaped, 2-5 em in diameter, with long petioles, arising from the stem nodes in rosettes. The stems (stolons) are slender, prostrate and often reddish coloured. The flowers are pale violet. Each umbel bears 2-5 fruits, enclosed within a thick, hard pericarp.
Centella asiatica is commonly mentioned as a ; rasayana in Ayurveda and for various ailmen including abdominal disorders. Rasayanas are advocated for use in rejuvenation therapy.l ! use as a therapy for leprosy is also well b documented and in folk medicine it is used particularly for treating wounds and for bronchitis, epilepsy, dysentery, fever, inflammation, leucoderma and as a nerve tonic.
The whole plant is used in jaundice, contagious abortion, foot and mouth disease, colic and swelling of the respiratory tract.
Asiatic acid, 6-hydroxy asiatic acid, madecassic acid, betulinic acid, thankunic acid and isothankunic acid are present together with their glycosides (up to 8%), depending on the country of origin of the plant. The major saponins are asiaticoside, asiaticoside A, asiaticoside B, madecassoside, braminoside, brahmoside, brahminoside, thankuniside and isothankuniside.
This constitutes about 0.1 % of the aerial parts and contains sesquiterpenoids (up to about 80%), with ?-caryophyllene, (X-humulene and germacrene-D, elemene and bicycloelemene, trans-farnesene being the most abundant:
Quercetin and kaempferol glycosides and astragalin have been found.
The leaf contains alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine and tryptop han.
Antiulcerogenic activity: The antiulcerogenic activity of the fresh juice of C. asiatica wasstudied against ethanol-, aspirin-, cold restraint stress- and pyloric ligation-induced gastric ulcers in rats. When given orally at doses of 200 and 600 mg/kg twice daily for 5 days, the drug showed significant protection against all the above experimental ulcer models. This effect was thought to be due to the strengthening of mucosal defensive factors. Oral administration of Centella extract (0.05, 0.25 and 0.50 g/kg) before ethanol administration significantly inhibited gastric lesion formation (by 58-82%) and decreased mucosal myeloperoxidase (MPO) activity in a dose-dependent manner. It prevented gastric mucosal lesions by strengthening the mucosal barrier and reducing the damaging effects of free radicals.
Spasmolytic activity: Activity was demonstrated when tested in vitro on isolated guinea pig ileum.
Wound-healing activity: A titrated extract of Centella asiatica (TECA), containing asiatic acid, madecassic acid and asiaticoside, and its separate components were evaluated for their effects in the wound chamber model. TECA-injected wound chambers were characterised by increased dry weight, DNA, total protein, collagen and uronic acid contents. Peptidic hydroxyproline was also increased, showing an increased remodelling of the collagen matrix in the wound. The three purified components ofTECA were all able to reproduce the effects of the complete drug. The activity of asiaticoside was studied in normal and delayed-type wound healing. In guinea pig punch wounds topical applications of a 0.2% solution of asiaticoside produced a 56% increase in hydroxyproline, 57% increase in tensile strength, increased collagen content and improved epithelialisation. In streptozotocin-diabetic rats, where healing is delayed, topical application of a 0.4% solution of asiaticoside over punch wounds increased hydroxyproline content, tensile strength, collagen content and epithelialisation, thereby facilitating healing. Asiaticoside was also active by the oral route at 1 mg/kg and is thought to be the main active constituent of Centella asiatica. Asiaticoside enhanced antioxidant levels at an initial stage of wound healing which may be an important contributory factor in the healing properties of this constituent. The extract also protected skin against radiation injury.
Immunomodulatory activity: An alcoholic extract showed stimulatory effect on the reticuloendothelial system (RES) in mice and an in vitro study of the aq ueous extract demonstrated a positive effect on both the classic and alternative pathways of complement activation.
Antitubercular activity: An injection of 0.5 ml of a 4% solution of hydroxyasiaticoside was given in guinea pigs, inoculated 15 days preyiously with tubercle bacillus. It reduced the number of tubercular lesions in the liver, lungs, nerve ganglions and spleen and decreased the volume of the spleen over that of untreated control animals, thereby displaying antitubercular activity.
Psychoneurological activity: The alcoholic extract, when given orally to rats and mice treated with phenobarbitone, significantly prolonged sleeping time. In the maximum electroshock-induced convulsion test in rats, it significantly reduced the duration of individual convulsions. In a behavioural test it reduced the duration of the immobility phase, indicating sedative, antidepressive and analgesic actions.
Antimicrobial activity: Asiaticoside at a concentration of 10 mglml showed antibacterial activity against Pseudomonas pyocyaneus and Trichoderma mentagrophytes.
Antiviral activity: The alcoholic extract showed antiviral activity against Herpes simplex type II virus.
Antilarval activity: A new triterpenoid glycoside 3-0-[ a- L-arabinopyranosyl] 2a,3 p, 6p ,23a - tetrahydroxyurs-12-ene- 28-oic acid exhibited dose-dependent growth inhibitory activity against larvae of Spilarctia obliqua.
The maximum tolerated dose of a 50% alcoholic extract in mice was found to be ? 250 mglkg. Allergic contact dermatitis and r photosensitivity have been reported after topical application.s Occasional burning pain . following injections, or the local application of powder, has been reported.
Dosha: Balances kapha and pitta