Method-dependent bias in the quantitation of cis- and trans-resveratrol glucosides by high performance liquid chromatography

The concentrations of cis and trans-polydatin (resveratrol 3-beta-glucoside ) were measured in 133 red wines by two methods: Method A utilized normal p hase HPLC with isocratic elution followed by UV detection, and Method B was based on reverse phase HPLC with gradient elution and photodiode array det ection. In each method, 20 mu L of sample was directly injected without pri or treatment. For both polydatin isomers, Method B gave higher values. These discrepancie s were more marked with the second of two Calibrators prepared by purificat ion of trans-polydatin from the dried roots of Polygonum cuspidatum. Overal l, the correlation coefficients for the two methods were only 0.442 and 0.7 04 for the cia and trans isomers, respectively, No explanation for these fi ndings was forthcoming. These results demonstrate the need for caution in i nterpreting and comparing values for polydatins reported using different me thods, and emphasize the need for pure synthetic standards of these compoun ds to allow valid interlaboratory and inter-method comparisons.