The pharmacological activity of Centella asiatica is thought to be due to several saponin constituents, including asiaticoside, asiatic acid, and madecassic acid. Extracts of C. asiatica, and in particular its major triterpene ester glycoside, asiaticoside, are valuable in the treatment of hypertrophic scars and keloids. Asiaticoside has been reported to decrease fibrosis in wounds, thus preventing new scar formation. The mechanism of action appears to be twofold: by increasing the synthesis of collagen and acidic mucopolysaccharides, and by inhibiting the inflammatory phase of hypertrophic scars and keloids. It has further been proposed that asiaticoside interferes with scar formation by increasing the activity of myofibroblasts and immature collagen. Triterpene compounds stimulate connective tissue repair and asiaticoside derivatives protect neurons from beta-amyloid toxicity
Pharmacokinetics
Madecassic acid crosses the skin rapidly but only to a limited extent. The plasma concentration did not exceed 0.02 to 0.05% of the initial applied concentration. Madecassoside is at the skin application site only 0.04% of the applied dose at 1 hour and about 0.06% after 24 hours. For asiatic acid similar results were observed. In man, active ingredients of Centella asiatica are excreted principally by faeces in a 24-76 hour period; smaller quantities are eliminated through the kidneys (EMEA 1998).