Novel Oxidations of (+)-Catechin by Horseradish Peroxidase and Laccase

Abstract

Horseradish peroxidase (HRP; EC 1.11.1.7) catalyzed the H(2)O(2)-dependent oxidative coupling of (+)-catechin 1 to form three different biphenyl C-C dimers 2-4, whereas Rhus vernicifera laccase catalyzed the formation of two new catechin-hydroquinone adducts 5 and 6. Spectroscopic evidence showed that HRP dimers were linked through position 8 of the A-ring of one catechin moiety to C-5' of ring B in 2 and 4 and to C-2 of ring C in 3. The unusual catechin dicarboxylic acid dimer 4 was obtained by ortho cleavage of the E-ring. Hydroquinone served as both a shuttle oxidant and a reactant by coupling at C-2' and C-5' of the catechin B-ring during laccase oxidations. HRP and laccase oxidation products were compared to D,L-alpha-tocopherol and (+)-catechin for their abilities to inhibit iron-induced lipid peroxidation in rat brain homogenates and Fe(3+)-ADP/NADPH in rat liver microsomes, as measured by the intensity of thiobarbituric acid reactive substance. All metabolites exhibited anti-lipid peroxidation with IC(50) values approximately 2-8 times higher than those of standard compounds. Characteristic reaction products may prove to be novel markers for (+)-catechin antioxidant reactions in living systems.

The Protective Effect of Grape Seed Extract on Cardiotoxicity Induced by Doxorubicin Drug in Male Rats

“…Phenolic antioxidants (PPH) inhibit lipid peroxidation by a rapid donation of hydrogen atom to the peroxyl radical (ROO) resulting in formation of alkyl (aryl) hydroperoxide (ROOH), as illustrated in the following reaction: ROO + PPH → ROOH + PP. The polyphenol phenoxyl radical (PP) produced can be stabilized by further donation of a hydrogen atom and formation of quinones [45], or by reacting with another radical, including another phenoxyl radical, to generate new components [60], thereby interrupting the initiation of a new chain reaction.…”

Laccase-mediated multi-step homo- and heteromolecular reactions of ortho -dihydroxylated aromatic compounds and mono- or diaminated substances resulting in C C, C O and C N bonds

“…S32-33). We measured various NMR sprectra -1 H NMR, 13 The first step for the formation of 8a-c is the postulated oxidation of 1d to o-quinone followed by a nucleophilic attack of the side chain nitrogen atom to the C5-position of the ring resulting in leukoadrenochrome which is oxidized to adrenochrome [45].…”

“…Some of the products may be biologically active e.g. antibacterial [10,11], antifungal [12], antioxidative [13,14] or anticancer [9].…”

Autooxidative Activity of Chlorogenic Acid and Damage to DNA

“…Catechins with structures similar to that of polyphenol [23] have been reported to produce hydrogen peroxide, semiquinone and superoxide radicals by their autooxidation [24,25] to induce DNA damage and diseases. In the autooxidizing process, cupric ion (Cu(II)) that is subject to be reduced, can improve the rate of autooxidation and generation of free radical intermediate [26,27]. There is also the potential for these antioxidants to behave as prooxidants under physiological conditions.…”