Further New Diterpenoids from Salvia miniata Fernald (Lamiaceae)

In course of our search on Salvia metabolites for the identification of new herbicides with diterpene and triterpene skeletons [1, 2] we have continued the study on Salvia miniata Fernald [3], a Mexican species whose aerial part exudate in a preliminary test showed anti-germinative activity against Papaver rhoeas L. and Avena sativa L., chosen on the basis of evaluating the seed germination response respectively of a common invasive species and of a common crop species. From Salvia miniata we had already isolated some new and known di- and triterpenes [4]; here we report two new compounds, obtained from the chromatographic separation of not previously considered fractions. The surface exudate, obtained by rinsing the plant material with CH2Cl2, and subjected to repeated column chromatography on Sephadex LH-20 and silica gel and to reversed-phase semi-preparative HPLC, yielded two new clerodane diterpenoids (1, 2) identified by IR and NMR analysis, including TOCSY, COSY, HSQC and HMBC experiments. [1] Vyvyan JR. Allelochemicals as leads for new herbicides and agrochemicals. Tetrahedron. 2002; 58: 1631–1646. doi:10.1016/S0040-4020(02)00052-2 [2] Dayan FE, Duke SO. Trichomes and root hairs: natural pesticide factories. Pesticide Outlook. 2003; 8: 175–178. doi:10.1039/b308491b [3] Epling C. A Revision of Salvia, subgenus Calosphace. In: Repertorium Specierum Novarum Regni Vegetabilis. Vol.110. Fedde F. Berkley, California: University of California Press,1940. [4] Bisio A, Romussi G, Russo E, Cafaggi S, Fraternale D, De Tommasi N. New Clerodane Diterpenoids from Salvia miniata Fernald (Lamiaceae). Planta Med. 2008; 74: 1041. doi:10.1055/s-0028-1084389