METHOD TO ASSAY THE CONCENTRATIONS OF PHENOLIC CONSTITUENTS OF BIOLOGICAL INTEREST IN WINES

We describe a reversed-phase HPLC method that uses gradient elution an d diode array detection to quantitate eight biologically active phenol ic constituents of wine: the cis and trans isomers of resveratrol and their glucosides, catechin, epicatechin, quercetin, and rutin, ODS Hyp ersil sewed as the stationary phase; the gradient was formed by acetic acid, methanol, and water, Each analysis required an equilibration pe riod of 10 min and a run time of 40 min for completion. Satisfactory p eak resolution was achieved following direct injection of a 20-mu L sa mple, and validation was accomplished by on-line spectral comparisons with known standards, Excellent linearity was obtained for all constit uents, and the detection limits ranged from 30 mu g/L (trans-resveratr ol) to 1.5 mg/L (catechin), Recoveries approximated 100% (range 95.2-1 05.5%), and the method provided good precision, with coefficients of v ariation between 1.17 and 3.38%. All of the phenolics measured were re asonably stable in opened wines protected against sunlight for up to 1 week at room temperature or 4 degrees C, but most showed losses of 10 -40% when stored for 6 weeks at either temperature.