Resveratrol (3,4,5-trihydroxy-trans-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 trans-conformation (4-hydroxystyryl moiety) was absolutely required for inhibition of cell proliferation. Enzymatic assays in vitro demonstrated that inhibition of DNA synthesis was induced by a direct interaction of resveratrol with DNA polymerases ␣ and ␦.

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Ischemic stroke is one of the main causes of death and disability. We investigated whether melanocortin peptides, which have protective effects in severe hypoxic conditions, also produce neuroprotection in a gerbil model of ischemic stroke. A 10-min period of global cerebral ischemia, induced by occluding both common carotid arteries, caused impairment in spatial learning and memory that was associated with activation of inflammatory and apoptotic pathways, including severe DNA damage and delayed neuronal death, in the hippocampus. Treatment with nanomolar doses of the melanocortin analog [Nle4, D-Phe7] alpha-MSH [which activates the melanocortin receptor subtypes (MC) mainly expressed in central nervous system, namely MC3 and MC4] modulated the inflammatory and apoptotic cascades and reduced hippocampus injuries even when delayed up to 9 h after ischemia, with consequent dose-dependent improvement in subsequent functional recovery. The selective MC3 receptor agonist gamma2-MSH had no protective effects. Pharmacological blockade of MC4 receptors prevented the neuroprotective effects of [Nle4, D-Phe7] alpha-MSH and worsened some ischemia outcomes. Together, our findings suggest that MC4 receptor-stimulating melanocortins might provide potential to develop a class of drugs with a broad treatment window for a novel approach to neuroprotection in ischemic stroke.

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