Gotu kola (Centella asiatica) is a medicinal plant that is native to India, parts of Asia, Australia and Madagascar. It is a flowering plants and lives in watery environments. The whole plant can be used medicinally as a treatment for various vascular conditions. The ability of gotu kola to improve the conditions of vascular tissue is likely due to its wound healing effects. The wound healing effects of gotu kola are apparent when it is used both externally and internally. The healing properties of gotu kola likely includes a stimulation of hair and nail growth, the development and maintenance of blood vessels into connective tissue, increase mucin, hyaluronic acid and chondroitin sulphate production, an increase in the tensile strength of the dermis, and an increased keratinisation of the dermis through a stimulative effect on the germinal layer of the skin. As a result of these physiological effects extracts of gotu kola are beneficial at treating burns, cellulite and disorders of the veins.
However, gotu kola also has a traditional use in Chinese medicine for the relief of anxiety and depression. In Ayurvedic medicine, gotu kola is used to cause relaxation during meditation. Therefore researchers have been interesting in understanding the possible anxiolytic effects of gotu kola extract, and some evidence suggests that gotu kola is an effective treatment for anxiety in humans. For example, in one study, researchers assessed the effects of a gotu kola extract on the acoustic startle response in healthy humans volunteers. The acoustic startle response means the subjects are exposed to a sudden noise and their reaction to it is measured. Subjects consumed either 12 grams of gotu kola or a placebo prior to exposure. The treatment with gotu kola was effective at reducing the size of the response to the stimuli at 30 and 60 min after consumption, compared to the placebo. This may suggest that gotu kola has anxiolytic effects in humans as the anxiety response is involved in this process.
Interaction with GABA neurotransmission is one of the ways that phytochemicals may show anxiolytic effects. The enzymes glutamic acid decarboxylase and GABA transaminase are both enzymes that can affect the GABA system and they may be targets for phytochemicals. Evidence suggests that gotu kola is able to interact with glutamic acid decarboxylase, and thus may affect brain levels of GABA. However differences in the chemical compositions of plants from various regions have been observed. And so the effects on anxiety may differ between batches of the herb. Standardised extract of gotu kola tend to come from those plants grown in Madagascar and typically contain around 30 % asiatic acid, madecassic acid and asiaticoside, as these has been identified as the primary active constituent of the plant. Levels of madecassoside in standardised extract may only be around 2 %. Other compounds present in extracts of gotu kola include quercetin and kaempferol and the essential oils camphor and cineole. A standardised extract is a way of ensuring a more consistent effect between different batches. Image of gotu kola leaf taken from wikipedia: Shashidhara halady (Own work) [CC BY-SA 4.0 (http://creativecommons.org/ licenses/by-sa/4.0)], via Wikimedia Commons.
The main active components in gotu kola are thought to be a group of phytochemicals belonging to the triterpene group. These include asiaticoside, madecassic acid and asiatic acid. The main therapeutic benefits may come from asiatic acid. Some evidence also suggests that asiaticoside is therapeutically active because it is converted to asiatic acid. For example, asiaticoside appears to be bioavailable in humans, as administration of 30 to 60 mg of asiaticoside from Centella asiatica cause an increase in blood levels of asiatic acid. Extracts of Centella asiatica at a dose of 500 mg per kg body weight and pure asiaticoside at a dose of 1 to 10 mg per kg body weight have been shown to have anxiolytic effects in rats. These anti-anxiety effects are seen in rats when exposed to stress through a maze test. Gotu kola extract may also increase sleep time in rats and decrease stress induced immobility when rats are forced to swim to fatigue. Cognition and antioxidant status may also be improved in rats through administration of gotu kola.
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