Photochemical hydroperoxidation of terpenes. Antimicrobial activity of alpha-pinene, beta-pinene and limonene hydroperoxides

The rose Bengal photosensitized oxidation of the (+) and (-) stereoisomers of alpha-pinene, beta-pinene and limonene has been optimized to produce suf ficient quantities of hydroperoxides for antimicrobial screening. Experimen tal conditions allowed the production of highly concentrated solutions of h ydroperoxides (approximately 2 M, approximately 30 w%). The antimicrobial a ctivity of each hydroperoxide solution was evaluated by measuring their min imum inhibitory concentration (MIC) (1,2). All the hydroperoxides behave as powerful antimicrobial agents (similar to hydrogen peroxide). The MIC valu es were almost independent of the nature of the parent terpene but depended of the nature of the bacterial colony (five conventional families, met in human pathologies, were tested).