Centella asiatica (L.) Urban. (Pennywort)
Centella asiatica (L.) Urban, synonym C. coriacea Nannfd, previously also named Hydrocotyle asiatica L. or H. lunata Lam, of the family Apiaceae, has numerous common names in various languages: pennywort, marsh pepperwort, Indian waternavelwort (English); asiatisches Wassernabelkraut (German); bevilaque, coquelariat, violette marron (French); gotu kola (Sri-Lanka); brahmi, brahmanduki, karivana, mandookaparni, babassa, thankuni, vellari, vallarai (Indian); talapetraka, anamanitra, korokorona, silabola (Malagasy); bodila-ba-dinku, tabao en Amhara (African); luo de da, ji xue cao (Chinese). The large number of native names, especially in India, also shows its popularity in the Ayurvedic system of medicine (Dandouau 1910).
C. asiatica () is a slender tropical herbaceous plant with crawling stems, propagating vegetatively by runners (stolons), with entire kidney-shaped leaves (1-3 cm long; 2-4 cm wide) bearing a crenate margin at the tip of long petioles (5 to 10 times the leaf length). In sunny places, the petioles are shorter (only 2x the leaf), and petioles and leaves become red due to important anthocyane production. Leaves and short peduncled (2-4-cm) inflorescences arise from a rosette near the ground. The umbels are reduced and contain mostly two to four white or pink-purple uniform small flowers (2 mm) consisting of five petals, five free stamens, a greatly reduced calyx, an inferior ovary with two carpels and a stylopodium supporting two styles. The fruit is a dry, flattened schizocarp with two single-seeded mericarps each with prominent ridges (Medicinal Plants of India 1976).
C. asiatica generally grows in damp, shadowed, or swampy areas, but also in savanna and secondary forest clearings under warm climates of both the northern and southern hemispheres. It is native to Asia and mainly found in India, Pakistan, and Madagascar; but the plant also grows in tropical and equatorial Africa, America, and the tropical regions of the New World.
Three varieties are described in relation to geographic origin which are correlated with some leaf morphology and chemical composition.
- – C. asiatica L. var. typica has weakly hairy, typically kidney-shaped leaves with well-crenulated margins, and is found in southern Asia, as far as Madagascar. All references in traditional medicinal concern this variety.
- – C. asiatica L. var. abyssinica shows suborbicular, with softer crenated margins, quite hairy leaves, and is present in tropical and equatorial Africa.
- – C. asiatica L. var. floridana with leaves longer than wide in shape, is found in America (from southern US to Argentina) and in tropical Oceania.
Each variety can show several chemical compositions: in India, the most frequent type of the variety typica contains asiaticoside and madecassoside, whereas a rarer one contains brahmoside and brahminoside.
Centella asiatica (L.) Urban. (Pennywort): Summary and Conclusion
Centella asiatica L. is known to contain active triterpenic compounds with an ursane ring system. Several unpublished studies have demonstrated that cell suspension cultures of this plant also contain asiatic acid, madecassic acid, and traces of asiaticoside. Our suspension culture has shown capacities to biotransform papaverine (with a benzylisoquinolein ring system) and thiocolchicine (with a tropolone ring system). The enzymatic demethylation and glucosylation system of thiocolchicine were extracted and the glucosyltransferase was partially purified.
The biotransformation of papaverine and thiocolchicine by Centella asiatica cell suspension culture shown in this work are two examples of the detoxifying of toxic compounds. Indeed, the papaveraldine product is significantly less toxic (1200mg/1) than papaverine (600mg/l). Thiocolchicoside was also known in animal cells to be less toxic than thiocolchicine. Oxidation of the substrate is the first step in detoxification, consisting in an increase in molecule polarity. The conjugation of glucose to the hydroxylic group of 3-demethylthiocolchicine leads to a product which may be accumulated probably in the vacuoles. In cell suspension culture of C. asiatica, this accumulation occurs with an increase in cell diameter and especially in vacuole diameter after addition of thiocolchicine. Storage of a glucosylated toxic compound like thiocolchicoside in the vacuoles appears to represent a convenient cellular mode to separate such a compound from its cytoplasmic tubulin target.
Selections from the book: “Medicinal and Aromatic Plants X”, (1998).