Structures and hepatocytotoxicity of co-occurring substances in oleanolic acid tablets

Tablets of oleanolic acid (OA) have been approved by SFDA in China as an adjuvant therapy for acute and chronic hepatitis. Co-occurring substances present in the tablets of OA and their hepatocytotoxicity have not yet been reported. In the current investigation, the crude OA drug was separated by repeated column chromatography. The structures of the isolated compounds were characterized by spectral analysis and the cytotoxicity of each compound was evaluated in vitro against the human normal liver cell L02 at concentrations from 0.125 to 1000 μmol/L using the MTT method. As a result, OA and its 11 co-occurring trace compounds including one new triterpenoid, 3-O- (4-oxopentanoyl)-olean-12- en-28-oic acid, were isolated and structurally characterized. Cytotoxicity tests indicated that these compounds were all non-toxic at concentrations up to 50μmol/L. Clear structure-activity relationship (SAR) was also observed. The results suggested that OA tablets of similar origin might not cause obvious cytotoxicity to the normal liver cell. The work may facilitate further SAR studies of OA-type triterpenoids.