Identification and quantification of triterpenoid centelloids in Centella asiatica (L.) Urban by densitometric TLC

A simple and rapid method for analysis of four major triterpenoids in Centella asiatica preparations is described. Thin-layer chromatography is widely used for saponin analysis; here it was used for identification and quantification of the pure compounds and the compounds in complex mixtures, by densitometric analysis after TLC. Ethanolic extracts of leaves from C. asiatica and authentic standards of asiatic acid, asiaticoside, madecassic acid, and madecassoside, were separated by normal-phase TLC with chloroform-methanol- acetic acid-water 60:32:12:8 (v/v) as mobile phase. These conditions enabled successful separation of the triterpenoid acids and their respective glycosides from other components of the crude extracts. The separated compounds were detected with anisaldehyde-sulfuric acid solution. The intensity of the resulting violet spots was proportional to the amount of saponin or sapogenin present. The correlation coefficients of calibration plots were between 0.9904 and 0.9982 and the plots were linear over the range 1.25-10 nmol standard, corresponding to approximately 0.6-5 μg for the acids and 1.2-10 μg for the glycosides. When the method was used for analysis of the specific saponins in C. asiatica leaves the results were consistent with literature reports.