Labdane diterpenes from Marrubium velutinum and Marrubium cylleneum

Abstract

From the aerial parts of Marrubium velutinum and Marrubium cylleneum, seven labdane diterpenes, velutine A, 15- epi-velutine A, velutine B, 15- epi-velutine B, velutine C, cyllenine A and 15- epi-cyllenine A, have been isolated together with five known diterpenes and four known flavones. The structures of the isolated compounds were established by means of NMR [ 1H– 1H–COSY, 1H– 13C–HMQC, HMBC, HMQC–TOCSY, NOESY] and MS spectral analyses. Complete NMR assignments are reported for known compounds.