Antibacterial activity of totarol and its potentiation.

Antimicrobial activity of six diterpenoids isolated from the bark of Podocarpus nagi (Podocarpaceae) has been tested against twelve selected microorganisms. Totarol [1], the most abundant compound among the six, exhibited potent bactericidal activity only against Gram-positive bacteria, among which Propionibacterium acnes was the most sensitive bacterium. Totarol also showed strong activity against four other Gram-positive bacteria tested: Streptococcus mutans, Bacillus subtilis, Brevibacterium ammoniagenes, and Staphylococcus aureus (both penicillin-resistant and penicillin-susceptible strains). The bactericidal activity of totarol was enhanced when it was tested in combination with several other natural products. Noticeably, the activity of totarol against Sta. aureus was increased eightfold when tested in combination with 1/2MIC of anacardic acid [9]. The synergistic activity of anacardic acid caused the minimum bactericidal concentration (MBC) of totarol to be lowered from 1.56 to 0.2 micrograms/ml.