QUANTIFICATION OF PHENOLIC COMPOUNDS IN DIETARY SUPPLEMENTS AND ANTIOXIDANT ACTIVITIES

Dietary supplements (DS) are products that are recommended for the treatment of various health issues, especially during the global pandemic, and the accuracy of the labeling information of these supplements plays a significant role in human health. In this study, a novel high performance liquid chromatography-diode array detector (HPLC-DAD) method was developed and validated to determine the accuracy of the labeling information of commercial dietary supplements containing phenolic compounds (rutin, quercetin, and resveratrol). The mobile phase, flow rate, and column temperature were optimized. Validation studies were carried out to prove the validity of the developed method. The limit of detection (LOD) and limit of quantification (LOQ) values of rutin, quercetin, and resveratrol were found in the range of 4.83-6.62 ng/mL and 16.09-22.07 ng/mL, respectively. Recoveries% were calculated in the range of 99.52-100.19% and 99.78-100.34% in the intra-day and inter-day analysis, respectively. The IC50 values of the dietary supplement extracts obtained by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method ranged from 0.08 to 0.76 mg/mL. Total Antioxidant Capacity (TAC) values of DS1, DS2, DS3, DS4, DS5, measured employing the Cupric Reducing Antioxidant Capacity (CUPRAC) method, were found to be 0.09, 0.03, 0.10, 0.10 and 0.40 mmol trolox per gram of extract, respectively.