Role of Hydrogen Peroxide in Bactericidal Action of Catechin

Abstract

Recently green tea, which is the traditional drink of Japan and China, has been recognized as healthful. Catechins, which are polyphenol chemical compounds found in abundance in green tea, possess physiological effects including antioxidative and bactericidal action as well as antitumor activity. Four main catechins are contained within green tea: epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC) and epigallocatechin gallate (EGCg). These catechins display strong antioxidant activity, 1) which efficiently eliminates reactive oxygen species. The antioxidant mechanism is believed to involve radical elimination by the phenolic hydroxyl group of the catechin structure.2) EGCg and EGC in catechin have demonstrated anti-tumor growth and a strong apoptosis induction effect in the human lung tumor cells H661 and H1299 and the induction was inhibited by catalase.3) This paper indicates that hydrogen peroxide participated in the apoptotic action of EGCg; however, the chemical mechanism has not been clarified.On the other hand, we noted previously that catechins exhibit a wide antibacterial spectrum of gram-negative bacteria and positive fungus in terms of germicidal action.4) The structure-activity relationship of catechin and bactericidal activity occurs in the following order: ECgϾEGCgϾEGCϾ EC.5) Furthermore, the gallate and pyrogallol moieties are necessary with respect to this activity. Investigation of EGCg uptake of liposomal membranes 6) and ultra-structure change on sterilization of trychophyton employing electron microscopy reveals that the action is based on the membrane injury action of bacterial cells. 7) Moreover, it has been reported that the bactericidal effect of EGCg is stronger for gram-positive bacteria than for gram-negative bacteria due to the difference in the amount of EGCg absorbed by the bacterial cell. EGCg was thought to carry a net negative charge in aqueous solution (pH 6-7); furthermore, it was believed to bind to the membrane component of bacteria as a result of electrostatic interaction, which led to membrane damage. 8)However, chemical elucidation of the mechanism via which EGCg causes membrane injury following binding to the liposome remains unclear. We previously established a highly sensitive analytical method for catechin using peroxalate chemiluminescent reaction.9) The principle is based on the reaction mechanism in which catechin reacts with dissolved oxygen in basic solution, resulting in the generation of active oxygen. In this study, we established that the reactive oxygen produced by catechin was hydrogen peroxide via chemiluminescent methodology and electron spin resonance (ESR) using a spin-trapping method. We believed that the hydrogen peroxide generation ability of EGCg was a central component with respect to bactericidal activity; consequently, examination was conducted in detail regarding the role of hydrogen peroxide-mediated bactericidal activity of EGCg and the effect of bactericidal activity of EGCg and hydrogen peroxide in terms of gram-negative (9 o...

Antimicrobial Activity of Gel-Entrapped Catechins toward Oral Microorganisms

“…Some reports have indicated that catechins promote the production of hydrogen peroxide. 40) From the results of our study, catalase prevented GEC-induced growth inhibition of S. mutans, A. naeslundii completely and the antimicrobial activity against S. mutans, A. naeslundii was dependent mainly on hydrogen peroxide. On the other hand, the inhibition zone became smaller in the case of S. aureus and no effect was observed against C. albicans.…”

Chromosome analysis of mouse zygotes after injecting oocytes with spermatozoa treated in vitro with green tea catechin, (−)-epigallocatechin gallate (EGCG)

“…While EGCG can protect cell membranes from lipid peroxidation [19,20], it can also act as a pro-oxidant. At concentrations higher than physiological levels, it produces hydrogen peroxide [2,10,21] that damages DNA and sperm membrane via lipid peroxidation [22,23]. Also, it inhibits sperm chromatin decondensation induced by dithiothreitol in human sperm [24].…”

Microbicidal Activity of Artificially Generated Hydroxyl Radicals

“…Since it has been reported that polyphenolic compounds exert antimicrobial effect via production of H 2 O 2 by auto-oxidation in a liquid medium [70,71], we tried to enhance the antimicrobial activity by means of exposure of polyphenolic compounds to blue light, which enhances the H 2 O 2 production through photo-oxidation of the compounds resulting in hydroxyl radical production via photolysis of the resultant H 2 O 2 ( Fig. 17.2).…”