Rapid and simultaneous determination of antioxidant markers and caffeine in commercial teas and dietary supplements by HPLC-DAD

A simple and fast reverse-phase high-performance liquid chromatography procedure coupled with photodiode array detector (RP-HPLC-DAD) was developed and validated for the analysis of major catechins, proanthocyanidin (procyanidin B2) and caffeine in 25 different natural complex matrices containing Camellia sinensis L. and/or grape seed extracts, two popular plant extracts that have been widely used as natural antioxidants in various food and beverage applications. Using an isocratic elution system, separation of all compounds was achieved within 12 min. Excellent linearity was observed for all of the standard calibration curves, and the correlation coefficients were above 0.9997. Limits of detection for all of the analyzed compounds ranged between 2.80×10−3 and 2.51×10−2 μg mL−1; limits of quantitation ranged between 9.30×10−3 and 8.36×10−2 μg mL−1. The developed method was found to be accurate and sensitive and is ideally suited for rapid, routine analysis of principal components in these well-known natural antioxidants.