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

This paper reports the study of the oxidation of resveratrol catalyzed by p olyphenol oxidase (PPO) as well as the effect of PPO, laccase and peroxidas e on the antiradical capacity of resveratrol (measured as capacity to scave nge 2,2'-azino-bis (3-ethylbenzthiazoline - 6 - sulfonic acid) radicals (AB TS(.))). Monophenolase activity of mushroom PPO in the presence of resverat rol showed the characteristic lag period (tau) prior the attainment of the steady state rate (V-ss). The Michaelis constant (K-m) for the oxidation of resveratrol catalyzed by PPO was 45 +/- 2 mu M at pH 6.8 and it decreased with pH. However, the maximum steady state rate (V-max) remained constant w ith pH. Both tau and V-ss depended on pH in a sigmoid way. Kinetic and NMR assays confirmed that this compound is a substrate which fulfilled both kin etic and structural reaction mechanisms of PPO. Neither laccase, nor PPO mo dified the antiradical capacity of resveratrol. However, resveratrol, in th e presence of peroxidase, lost its antiradical capacity. A possible correla tion between antiradical capacity of resveratrol and its oxidation status i s proposed. This paper tries to increase the knowledge about this promising health-beneficial molecule and to demonstrate that PPO could be involved i n the oxidation pathway of resveratrol.