Diterpenoid constituents of the roots of Salvia digitaloides

Salvia digitaloides, belonging to the economically and medicinally important genus Salvia, is distributed in the northwest of Yunnan Province, People's Republic of China. The roots of this plant were soaked in alcohol by local Tibetans to make a special traditional "red wine", and many local people like to drink this traditional "red wine" to strengthen physical health. To investigate the bioactive diterpenoid constituents of the roots, a detailed phytochemical study was carried out, and 13 diterpenoids including two new norditerpenoids, dihydroneotanshinlactone (1) and 16,17-dinorpisferal A (2), were isolated. Their structures were established on the basis of detailed spectroscopic analysis. In addition, computational methods were applied to validate the stereochemistry of compound 1. For the bioassay to inhibit the growth of five tumor cell lines, neotanshinlactone (3) exhibited selective cytotoxic activity toward the human breast cancer cell line SK-BR-3, while the other four tanshinones (4-7) showed significant toxicity effects against all of the tested five cell lines.