Determination of diosgenin content in medicinal plants with enzyme-linked immunosorbent assay

Many medicinal plants contain diosgenin, which has a significant medicinal value. However, there is currently no effective and rapid analytical method to determine the diosgenin content of plants or products. In the present work we have developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of diosgenin in herbal medicines. Diosgenin was conjugated with bovine serum albumin (BSA) for immunization. A polyclonal antibody developed in rabbits against a diosgenin-BSA conjugate was shown to be specific for diosgenin. The developed ELISA assay was highly sensitive, specific, and easy to perform. In addition, it gave more precise results with less variation than other methods that have been used in the past, including gravimetric and spectrophotometric assays, and correlated well with high-performance liquid chromatography. The diosgenin content determined by ELISA varied widely, with the highest and lowest values in rhizomes or tubers of Paris polyphylla and Dioscorea opposita Thunb. "Jiao-ban Yam", respectively, differing by more than 9000-fold. These results suggest that the ELISA method can be used as a rapid, simple, sensitive, and accurate tool for quantitative analysis of samples containing diosgenin, and may provide an important criterion for quality evaluation and a valuable tool for quality control of diosgenin-containing medicinal plants.