Phytotoxic activity and a new clerodane diterpenoid from the exudate of the aerial parts of Salvia buchananii Hedge.

In the course of our study on Salvia species with potential interest for phytotoxic activity we considered Salvia buchananii Hedge (Hedge, 1963) whose exudate showed activity against Papaver rhoeas L. and Avena sativa L. in a preliminary test (Bisio et al., 2010). The mixture, obtained by rinsing the plant material with CH2Cl2, was subjected to repeated column chromatography on Sephadex LH-20. Some of the obtained fractions showed a good phytotoxic activity. A preliminary separation of one of the active fractions by chromatography on silica gel and HPLC-HRMS experiments followed by semi-preparative RP-HPLC, yielded a new clerodane diterpenoid (1), identified by IR and NMR analysis, including TOCSY, COSY, HSQC and HMBC experiments, and HR-MS analysis