Isolation of two bioactive ent-kauranoids from the leaves of Isodon xerophilus

Isodon xerophilus has been used as a herbal cold tea for the prevention and treatment of sore throat and inflammation in southernwestern China. A phytochemical study on the ethyl acetate (EtOAc) soluble fraction of I. xerophilus leaves led to the isolation of two new ent-kauranoids, xerophinoids A (1) and B (2), together with 14 known diterpenoids. The structures of xerophinoids A (1) and B (2) were illustrated using spectroscopic methods including 1D and 2D NMR analyses. To study their biological activities, the effects of xerophinoids A (1) and B (2) on nitrite production, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta were examined. In addition, xerophinoids A (1) and B (2) also exhibited potent cytotoxicity against several human tumor cell lines (IC50 < 11 microM), but they had no toxicity on human T-lymphocyte (C8166).