STUDIES ON THE ENZYME-IMMUNOASSAY OF BIOACTIVE CONSTITUENTS IN ORIENTAL MEDICINAL DRUGS .6. ENZYME-IMMUNOASSAY OF GINSENOSIDE RB1 FROM PANAX-GINSENG

Enzyme immunoassay (EIA) of ginsenoside Rb1 (GRb1), one of the glucosides of protopanaxadiol from Panax ginseng, was explored. A carrier protein (bovine serum albumin (BSA)) was coupled to the C-26 position on the unsaturated side chain of the protopanaxadiol moiety to prepare the immunogen. In order to perform bridge heterologous EIA, a label (beta-D-galactosidase) was introduced at C-26 of the saturated side chain to obtain labeled antigen. Anti-GRb1 antisera were elicited in rabbits by immunization with GRb1-BSA conjugate (9). The double antibody method (with goat anti-rabbit IgG antiserum) was used to separate the bound and free GRb1-beta-Gal. A satisfactory standard curve for EIA of GRb1 was obtained in the range of 0.04-10 ng/tube. In a comparison of the assay results obtained by EIA and HPLC, the linear regression equation and correlation coefficient for the two methods were y(EIA) = 9.18x(HPLC)-0.033 and 0.98, respectively. The anti-GRb1 antiserum cross-reacted with GRb2 (21.8%) and GRc (10.6%), which are also constituents of Panax ginseng.