Heat treatment enhances the antimicrobial activity of (+)‐Catechin when combined with copper sulphate. (30th August 2015)

• Record Type: Journal Article
• Authors: Holloway, A.C.; Mueller‐Harvey, I.; Gould, S.W.J.; Fielder, M.D.; Naughton, D.P.; Kelly, A.F.
• Is Part Of: Letters in applied microbiology. Volume 61:Number 4(2015:Oct.)
• Page Start: 381
• Page End: 389
• Publication Date: 2015-08-30
• Subjects: Microbiology -- Periodicals; 660.62
• DOI: 10.1111/lam.12472
• Languages: English
• ISSNs: 0266-8254

Abstract

<abstract abstract-type="main" id="lam12472-abs-0001"> <title>Abstract</title> <sec id="lam12472-sec-1011" sec-type="section"> <p>The aim of the study was to compare the antimicrobial activities of freshly made, heat‐treated (HT) and 14 day stored (+)‐Catechin solutions with (+)‐catechin flavanol isomers in the presence of copper sulphate. (+)‐Catechin activity was investigated when combined with different ratios of Cu<sup>2+</sup>; 100°C heat treatment; autoclaving; and 14 day storage against <italic>Staphylococcus aureus</italic>. Cu<sup>2+</sup>‐(+)‐Catechin complexation, isomer structure‐activity relationships, and H<sub>2</sub>O<sub>2</sub> generation were also investigated. Freshly made, HT, and 14 day stored flavanols showed no activity. While combined Cu<sup>2+</sup>‐autoclaved (+)‐Catechin and ‐HT(+)‐Catechin activities were similar, HT(+)‐Catechin was more active than either freshly made (+)‐catechin (generating more H<sub>2</sub>O<sub>2</sub>) or (−)‐Epicatechin (though it generated less H<sub>2</sub>O<sub>2</sub>) or 14 day‐(+)‐Catechin (which had similar activity to Cu<sup>2+</sup> controls—although it generated more H<sub>2</sub>O<sub>2</sub>). When combined with Cu<sup>2+</sup>, 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<sup>2+</sup> 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<sup>2+</sup> complexes. The HT(+)‐Catechin complex generated more H<sub>2</sub>O<sub>2</sub> which could explain its higher antimicrobial activity.</p> </sec> <sec id="lam12472-sec-1012" sec-type="section"> <title>Significance and Impact of the Study</title> <p>Natural products attract considerable attention in the search for novel antimicrobials, prebiotics and antioxidants. Enhanced biological activity of natural products has been demonstrated with chemical and heat treatment. This article extends the few publications on heat treatments of plant products and combinations with adjuncts, to raise antimicrobial activity against pathogens such as <italic>Staphylococcus aureus</italic>. We demonstrated that heat treatment could increase the activity of (+)‐Catechin, a weak antimicrobial flavanol found commonly in plants in the presence of copper sulphate. Heat treatment of readily available resources merits consideration in the development of more potent substances for use in clinical settings and agriculture.</p> </sec> </abstract>