Antimicrobial diterpenes from the seeds of Cephalotaxus harringtonia var. drupacea

Six diterpenes, including two new natural products, were isolated from the seeds of Cephalotaxus harringtonia. The new metabolites were characterised as 8 beta-hydroxy-9(11),13-abietadien-12-one and 5,6-didehydroferruginol, while the known compounds were identified as ferruginol, sugiol, 6,12-dihydroxyabieta-5,8,11,13-tetraen-7-one, and abieta-8,11,13-trien-7 beta-ol. These compounds were studied in vitro for their antimicrobial activity against clinically isolated bacteria and Candida strains. Ferruginol and 6,12-dihydroxyabieta-5,8,11,13-tetraen-7-one showed antimicrobial activity against Gram-positive bacteria. None of the six diterpenes was active against the Gram-negative organisms and yeasts tested.