Heat treatment enhances the plant phenolic (+)-catechin, a weak antimicrobial agent when combined with copper sulphate

Holloway, A. C., Mueller-Harvey, I., Gould, S. W. J., Fielder, M. D., Naughton, D. P. and Kelly, A. P. (2015) Heat treatment enhances the plant phenolic (+)-catechin, a weak antimicrobial agent when combined with copper sulphate. Letters in Applied Microbiology, 61(4), pp. 381-389. ISSN (print) 0266-8254

Abstract

The aim of the study was to compare the antimicrobial activities of freshly-made, heat-treated (HT), and 14 d stored (+)-Catechin solutions with (+)-catechin flavanol isomers in the presence of copper sulphate. (+)-Catechin activity was investigated when combined with different ratios of Cu(2+) ; 100°C heat treatment; autoclaving; and 14 d storage against Staphylococcus aureus. Cu(2+) -(+)-Catechin complexation, isomer structure-activity relationships, and H2 O2 generation were also investigated. Freshly-made, HT, and 14d stored flavanols showed no activity. Whilst combined Cu(2+) -autoclaved (+)-Catechin and -HT(+)-Catechin activities were similar, HT(+)-Catechin was more active than either freshly-made (+)-catechin (generating more H2 O2 ) or (-)-Epicatechin (though it generated less H2 O2 ) or 14d-(+)-Catechin (which had similar activity to Cu(2+) controls - though it generated more H2 O2 ). When combined with Cu(2+) , in terms of rates of activity, HT(+)-Catechin was lower than (-)-Epigallocatechin gallate and greater than freshly-made (+)-Catechin. Freshly-made and HT(+)-Catechin formed acidic complexes with Cu(2+) as indicated by pH and UV-vis measurements although pH changes did not account for antimicrobial activity. Freshly-made and HT(+)-Catechin both formed Cu(2+) complexes. The HT(+)-Catechin complex generated more H2 O2 which could explain its higher antimicrobial activity. This article is protected by copyright. All rights reserved.

Actions (Repository Editors)

Item Control Page Item Control Page