Studies on the enzyme immunoassay of bio-active constituents in oriental medicinal drugs. VI. 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.