Isolation and HPLC profiling of chemical constituents of Saraca asoca stem bark

摘要

Saraca asoca (Roxb.) de Wilde, a common tree of India, is popularly used in the ayurvedic and modern herbal systems of medicine for genito-urinary problems of women. In the current herbal market there happens to be mixing of adulterants with authentic S. asoca stem bark. In order to identify the right bark material, there exists hardly any laboratory testing possibilities to authenticate the stem bark samples.' The n-hexane, methanol and aqueous methanol extracts have been investigated by isolating and characterizing major compounds and developing the HPLC profiling of methanol and aqueous methanol extracts. The n-hexane, methanol and 60% aqueous methanol extracts of stem bark of S. asoca after isolation, have yielded a total of 17 compounds whose structures were established by spectroscopic methods. A series of experiments were run to develop the HPLC conditions for the chemical profiling of the bark. The n-hexane extract has been found to contain mainly triterpenoids and sterols while methanol extract has yielded several flavanol derivatives along with a few triterpenoids. The aqueous methanol extract afforded flavanol derivatives. Out of the isolated compounds, ursolic acid, lupeol, glochidiol, 5,3'-dimethoxy epicatechin, 3'-eoxyepicatechin-3-O-beta-D-glucopyranoside, 3'-deoxycatechin-3-O-alpha-L-rhamnopyranoside and epigallocatechin have been isolated from S. asoca bark for the first time. HPLC profiling of methanol and aqueous methanol extracts of the bark has been developed by using mainly the isolated compounds as references. The percent composition of the major compounds was determined by HPLC and can be used to monitor the possible adulterations in the commercial bark materials. The antibacterial tests showed that the methanol and aqueous methanol extracts and few compounds have mild activity on some of the bacterial strains whereas they did not show any antifungal activity.