Specific Structural Determinants Are Responsible for the Antioxidant Activity and the Cell Cycle Effects of Resveratrol

TLDR

Resveratrol, a natural phytoalexin from grapes and wine, exhibits antioxidant and antiproliferative activities. The study examined whether these antioxidant and antiproliferative effects are governed by the same or distinct structural features of the molecule. Derivatives with selective methylation of hydroxyls, modified double bond, and stereochemistry were synthesized and tested for antioxidant activity (citronellal thermo‑oxidation, DPPH radical, lipid peroxidation) and antiproliferative activity (clonogenic assay, cell‑cycle analysis, DNA‑synthesis assays). The 4′‑hydroxyl alone does not determine antioxidant activity, whereas the 4′‑OH together with trans stereochemistry is essential for inhibiting cell proliferation, and resveratrol directly blocks DNA synthesis by interacting with polymerases α and δ.

Abstract

Resveratrol (3,4′,5-trihydroxy-<i>trans</i>-stilbene) is a natural phytoalexin found in grapes and wine, which shows antioxidant and antiproliferative activities. In this study we have investigated whether these properties are dependent on similar or different structural determinants of the molecule. To this purpose, resveratrol derivatives, in which all or each single hydroxylic function were selectively substituted with methyl groups, were synthesized. Analogues with the stilbenic double bond reduced or with the stereoisomery modified were also investigated. The antioxidant activity of these compounds was evaluated by measuring the inhibition of citronellal thermo-oxidation, or the reduction of 2,2-diphenyl-1-picrylhydrazyl radical. In addition, the protection against lipid peroxidation was determined in rat liver microsomes, and in human primary cell cultures. The antiproliferative activity was evaluated by a clonogenic assay, and by analysis of cell cycle progression and DNA synthesis. The results showed that the hydroxyl group in 4′ position is not the sole determinant for antioxidant activity. In contrast, the presence of 4′-OH together with stereoisomery in the <i>trans-</i>conformation (4′-hydroxystyryl moiety) was absolutely required for inhibition of cell proliferation. Enzymatic assays <i>in vitro</i> demonstrated that inhibition of DNA synthesis was induced by a direct interaction of resveratrol with DNA polymerases α and δ.