Development of an improved reverse-phase high-performance liquid chromatography method for the simultaneous analyses of trans-/cis-resveratrol, quercetin, and emodin in commercial resveratrol supplements.

The objectives of the study were to develop a reverse-phase high-performance liquid chromatography method for the simultaneous analyses of trans-/cis-resveratrol, emodin, and quercetin and to determine the concentrations of these polyphenols in 28 resveratrol supplements. Samples were separated within 15 min in a C18 reversed-phase column using mobile phases containing 0.1% formic acid and methanol/0.1% formic acid. The calibration graphs for all four compounds were linear from 0.1 to 410 μg/mL (r2=0.99). The concentration of resveratrol as stated on the labels was often different from the analytical results, with 21 and 11% of the total supplements having low or high values, respectively. Many of the supplements also contained variable but generally low levels of emodin, a compound known to cause diarrhea. The proposed method is a rapid, sensitive, accurate, and cost-effective procedure that can be used for the simultaneous quantification of four polyphenols in resveratrol supplements.