Algal growth inhibition effects and inducement modes by plant-producing phenols

Evaluated here are the inhibitory effects on blue-green algae (Microcystis aeruginosa) produced by nine plant-producing phenols (caffeic, p-coumaric, ferulic, protocatechuic, sinapic, syringic, and vanillic acids, catechol, a nd hydroquinone), two plant-produced acids (quinic and shikimic acid), phen ol, resorcinol, hydroxy hydroquinone, and phloroglucinol. Algal assays conf irmed growth inhibition of M. aeruginosa by polyphenols, i.e., caffeic/prot ocatechuic acid, catechol, hydroquinone, hydroxy hydroquinone. and phlorogl ucinol, and by phenols containing methoxy groups, i.e., vanillic, sinapic, and syringic acids. Accordingly, this indicates good feasibility for contro lling growth of M. aeruginosa using such plant-producing polyphenols and/or phenols as additives. A comparison of the inhibitory effects of the polyph enols showed that those induced by polyphenols in which phenolic hydroxy gr oups bound a benzene ring at ortho- and/or para-positions to another phenol ic hydroxy group are stronger than the effects induced by polyphenols in wh ich phenolic hydroxy groups are at only meta-positions. Experiments showed that the only polyphenols demonstrating significant growth inhibition of M. aeruginosa were autoxidized. These results suggest that autoxidation of th e polyphenols induces inhibitory effects by producing polyphenol-autoxidize d products such as radicals. (C) 2001 Elsevier Science Ltd. All rights rese rved.