Method to assay the concentrations of phenolic constituents of biological interest in wines

We describe a reversed-phase HPLC method that uses gradient elution and diode array detection to quantitate eight biologically active phenolic constituents of wine: the cis and trans isomers of resveratrol and their glucosides, catechin, epicatechin, quercetin, and rutin, ODS Hypersil sewed as the stationary phase; the gradient was formed by acetic acid, methanol, and water, Each analysis required an equilibration period of 10 min and a run time of 40 min for completion. Satisfactory peak resolution was achieved following direct injection of a 20-mu L sample, and validation was accomplished by on-line spectral comparisons with known standards, Excellent linearity was obtained for all constituents, and the detection limits ranged from 30 mu g/L (trans-resveratrol) to 1.5 mg/L (catechin), Recoveries approximated 100% (range 95.2-105.5%), and the method provided good precision, with coefficients of variation between 1.17 and 3.38%. All of the phenolics measured were reasonably 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.