¹Department of Pharmacognosy, Faculty of Pharmacy, Trakya University, Balkan Campus, 22030, Edirne, Türkiye
²Department of Pharmacognosy, Faculty of Pharmacy, Yeditepe University, Kayışdağı, 34755, İstanbul, Türkiye DOI : 10.12991/jrp.2019.00 The utilization of nutraceuticals consisting of (trans)-resveratrol or quercetin or combination of these two compounds or food supplements contain extracts rich with (trans)-resveratrol or quercetin have become very popular due to their protective and health-beneficial effects especially after the Coronavirus 2019 (COVID-19) pandemic. As the safety and quality control of the food supplements is very important in terms of well-being of consumers, the objective of this study was to qualitatively analyze commercially available (trans)-resveratrol and/or quercetin supplements sold in the Turkish market by using High-Performance Thin-Layer Chromatography (HPTLC) and to measure trans-resveratrol and quercetin quantitatively by using a newly developed and validated High- Performance Liquid Chromatography (HPLC) method. The HPTLC analysis was performed on silica gel 60 F254 glass HPTLC plates using toluene-chloroform-ethyl acetate-formic acid (3:2:10:0.1, v/v/v/v) as a developing solvent system. Standard compounds trans-resveratrol and quercetin were parallelly analyzed with sample test solutions belong to different brands. The chemical fingerprintings of analyzed samples showed that 8 of the 33 of them did not exhibit the expected zones corresponding to reference compounds. According to quantitative analysis via HPLC, the determined contents of trans-resveratrol and quercetin were found to be different from the declared amounts in all of the investigated products. The deviation of determined trans-resveratrol content from the declared content was calculated as ± 10.0% in only four food supplements (R4, R5, R8, QR4; percent of declared trans-resveratrol contents ranged between 90.3% and 101.2 %), whereas deviation of quercetin levels was found higher in all quercetin containing products. To conclude, the majority of the marketed products containing (trans)-resveratrol and/or quercetin in Türkiye had lower levels of the active compounds indicating the inconsistency between the declared and the actual content of these substances. It should be highlighted that quality control of food supplements must be done by authorities before marketing. Keywords : Trans-resveratrol; Quercetin; Nutraceuticals; Food supplements; High-Performance Thin-Layer Chromatography; High-Performance Liquid Chromatography; Quality control