Study of the oxidation of resveratrol catalyzed by polyphenol oxidase. Effect of polyphenol oxidase, laccase and peroxidase on the antiradical capacity of resveratrol

Abstract

This paper reports the study of the oxidation of resveratrol catalyzed by polyphenol oxidase (PPO) as -well as the effect of PPO, laccase and peroxidase on the antiradical capacity of resveratrol (measured as capacity to scavenge 2,2'-azino-bis (3-ethylbenzthiazoline - 6 - sulfonic acid) radicals (ARTS')). Monophenolase activity of mushroom PPO in the presence of resveratrol showed the characteristic lag period (τ) prior the attainment of the steady state rate (Vss). The Michaelis constant (Km) for the oxidation of resveratrol catalyzed by PPO was 45 ± 2 μM at pH 6.8 and it decreased with pH. However, the maximum steady state rate (Vmax) remained constant with pH. Both τ and Vss depended on pH in a sigmoid way. Kinetic and NMR assays confirmed that this compound is a substrate which fulfilled both kinetic and structural reaction mechanisms of PPO. Neither laccase, nor PPO modified the antiradical capacity of resveratrol. However, resveratrol, in the presence of peroxidase, lost its antiradical capacity. A possible correlation between antiradical capacity of resveratrol and its oxidation status is proposed. This paper tries to increase the knowledge about this promising health-beneficial molecule and to demonstrate that PPO could be involved in the oxidation pathway of resveratrol.