Triterpenoid saponins in tea (Camellia sinensis) plants: biosynthetic gene expression, content variations, chemical identification and cytotoxicity

Very little is known about saponins in tea and their biosynthesis in tea plants despite of the importance. Here, we studied tea saponins and their biosynthesis genes. Saponins were promptly recovered in tea infusions. Cytotoxicity of tea saponin extracts on human tongue squamous and hepatocellular carcinoma lines showed respective IC50 values of 29.2 and 17.5 μg/mL, which may be attributable to over 40 saponins identified in green tea. Saponin contents varied in shoot tips of 42 tea plant varieties but did not change drastically during tea processing. Saponin biosynthetic gene expression was consistent with its contents in plant tissues. Thus, plant tips produce significant amounts of saponins, which are stable during tea processing, and ready to be recovered to tea infusions to provide potent health benefits to consumers. This study paves a road towards clarifying the biosynthesis and genetic improvement of saponins in tea plants.