The Protective Role of Flavonoids against Toxic Factors on Phospholipid Membranes

Flavonoids are plant secondary metabolites that insure the proper growth, development and protection of plants. Both in vivo and in vitro, they exhibit a broad biological activity that in many cases is connected with their antioxidative ability. The diversified ring structure of a flavonoid molecule with conjugated double bonds and numerous hydroxyl substituents ensures their antioxidative action. The long exposure of an organism to the action of free radicals induces cell damage on the molecular level, which may result in dangerous diseases. Organic compounds of tin and lead, as follows from our earlier investigations, interact strongly with the lipid phase of biological membranes, modifying their operation, and thus being toxic. This toxicity may also result from some organometallic compounds, e.g. triphenyl-and tributyltin, which are toxic under some conditions. The objective of this research was to estimate the protective role of flavonoids towards liposome phosphatitylcholine membranes exposed to the simultaneous action of free radicals (induced by UV radiation) and the organic forms of tin. The antioxidative ability of flavonoids in vitro (parameter IQ 50) was assumed as a measure of their protective role. Moreover, to suggest a possible antioxidation mechanism of flavonoids, their antiradical activity towards the radical DPPH was investigated. Also, the possibility of interaction between components of the system was estimated in the process of flavonoid association with organometallic compounds. The results obtained indicate a high and differentiated antioxidative, antiradical and chelating activity of the antioxidants studied. They suggest a possible mechanism of the antioxidative action of flavonoids as free radical scavengers and chelaters of organometallic compounds. The complexing properties of flavonoids with respect to toxic forms of tin also indicate a possibility of their application as detoxicants.