Preparation of Polyclonal Antibody against Ganoderic Acid A and Establishment of Enzyme Linked Immunosorbent Assay

The conjugated antigen of ganoderic acid A was synthesized by the active ester method using bovine serum albumin as a carrier and was used as an immunogen to immunize rabbits according to the immunization procedure to obtain the polyclonal antibody against the conjugated antigen. After analyzing the titer and target of the polyclonal antibody, an indirect competitive-enzyme linked immunosorbent assay (ic-ELISA) for ganoderic acid A was established. The results showed that the polyclonal antibody included idiotypic antibodies targeting three regions of the conjugated antigen, with a total titer of 1:78125, and a titer of 1:3125 for specific anti-ganoderic acid A antibody. The detection limit of ganoderic acid A was 0.3 μg/L, and the median inhibitory concentration was 4.0 μg/L. The linearity range of this method was 0.6–27.3 μg/L. The inter-batch coefficient of variation was less than 10%, and the recoveries for spiked samples were between 82.9% and 118.6%. The results of determination of 22 commercial samples of Ganoderma lucidum powder showed that there was a significant difference in ganoderic acid A contents among different brands. The correlation coefficient between the results of this method and those obtained by high performance liquid chromatography (HPLC) was 0.972. The results showed that ic-ELISA was feasible for the determination of ganoderic acid A. This method can provide an auxiliary scheme for the quality control of related products in the G. lucidum health product market.