Diterpenos tipo abietano isolados de Plectranthus barbatus Andrews

Plectranthus barbatus is largely used in the Northeast region of Brazil by the local population for treatment of digestive problems as substitute of boldo (Pneumus boldus). Phytochemical analysis of the leaf extracts of Plectranthus barbatus (Labiatae) cultivated in this region yielded two abietane diterpenoids, cyclobubatusin (1) and barbatusin (2) and a new one named 7b-acetyl-12-deacetoxycyclobutatusin (3). The structures of the isolated compounds were established by spectral analysis, using mainly mass spectra and 1H and 13CNMR (1D and 2D). These procedures permitted the assignment of all chemical shifts in the diterpenoids.