Antimicrobial Abietane-Type Diterpenoids from Plectranthus punctatus

Four new para-benzoquinone containing abietane-type diterpenoids (1-4) along with thirteen known diterpenoids (5-17) were isolated from the roots of Plectranthus punctatus. The structures of the compounds were established by detailed spectroscopic analyses and comparison with literature data. The compounds were tested for their antibacterial and cytotoxic activity and showed significant inhibitory activity against all bacterial strains used, with compounds 6, 8, 10, and 11 showing an inhibition zone for Staphylococcus warneri even greater than the reference drug, gentamycin.