Antioxidant action of two polyphenols, resveratrol and piceid, on a biological model in vitro.

Among natural antioxidants found in many natural foods and beverages, the flavonoid resveratrol and piceid have been proven to be effective against a broad range of diseases whose origin can be attributed to oxidative damage. Resveratrol is a phytoalexin, a secondary metabolite synthesized by Spermatophytes in response to stress conditions caused, for example, by exposure to UV radiation or fungal infection. Piceid, called also polidatina, is the glucosylated form of resveratrol, and, as its parental compound, also shows two isomers cis and trans; it is more resistant to enzymatic oxidation of resveratrol, enters the cell through an active transport mechanism that uses the glucose transporters, and, because of its higher solubility in water, is more efficiently absorbed from the mammal’s intestine. This work was planning to evaluate the antioxidant action of these polyphenols on a biological model in vitro and to assess, then, any protective action of these stilbenes when the same organelle are exposed to toxic environmental substances known to give rise to a state of oxidative stress. The choice of using a mitochondria-based bioassay was determined by the need to clarify the biochemical mechanisms underlying the antioxidant effect of resveratrol and piceid on natural membranes. In particular, starting from some studies conducted to date on model membranes (i.e. synthetic organelles like micelles or liposomes), we tried to investigate resveratrol and piceid antioxidant action performed at mitochondrial membranes, using frozen beef heart mitochondria. Initially, they has been utilized with the classical mitochondrial endpoint, i.e. respiratory chain inhibition. Then, because it is reported that the antioxidant activity of polyphenols is linked to their ability to block or slow down the lipid peroxidation, reacting with peroxy radicals formed in the propagation phase, we investigated the ability of resveratrol and piceid to interact with initiator radicals, since the possibility exists that oxidation is inhibited at the stage of initiation. Indeed, the action of resveratrol and piceid as a scavenger against radical initiators and propagators of membrane oxidation, and its effectiveness in preventing the lipid peroxidation in different types of substrates, is well known.