Seasonal variation in the total saponin content of platycodon roots cultivated in Japan

Roots of Platycodon grandiflorus A. De Candolle (Campanulaceae), with the bark removed, have been used as food and frequently employed as herbal medicines for inflammatory diseases such as tonsillitis, dermatitis, and cough. Platycodins are the bioactive saponin components of these crude medicines. Recently, P. grandiflorus have been cultivated in Japan and are harvested from October to December according to conventional practices. Seasonal fluctuations in the total saponin content of these roots were determined using LC/MS methods to recommend harvesting times when the saponin content is high. Platycodins A and C are monoacetylated forms of platycodin D; however, the acetyl form is unstable and deacetylates easily. Here, the contents of platycodin D, platycodin D₂, and platyconic acid A were measured as the total saponin content using alkaline hydrolysis for monoacetylated platycodins D, D_2, and platyconic acid A. The results demonstrated that the saponin content in the roots decreased in summer, increased in autumn, but decreased again in late autumn.