Determination of resveratrol in preparations containing Vitis vinifera L. extract sold in Turkey

In this thesis study, phytochemical analyses were carried out to test the declared amount of resveratrol on the label of 11 Vitis vinifera L. (grape) seed extract/resveratrol containing dietary supplements sold in pharmacies. For this purpose, thin layer chromatography (TLC) and liquid chromatography-quadrupole time of flight mass spectrometry (LC-QTOF-MS) methods were employed. In addition, for determination of the antioxidant activities of the samples; 1,1-diphenyl-2-picrylhydrazil (DPPH) free radical scavenging activity, N,N-dimethyl-p-phenylenediamine (DMPD•+) radical scavenging activity, ferric-reducing antioxidant power (FRAP), and metal-chelation activities were performed. It was determined that, among the tested samples, only one, out of 11 samples, complied with the GMP requirements (95-105% active ingredient content), whereas the contents of the other samples were not in accordance with the label information. Our findings indicated once more importance of that all dietary supplements must be produced in accordance with GMP rules, meet the content given in the label declaration, and must be sold in pharmacies under pharmacist concultancy in order to ensure the expected health-benefiting effect by dietary supplements in terms of public health.