A new UHPLC-MS/MS method for the determination of flavonoids in supplements and DPPH-UHPLC-UV method for the evaluation of the radical scavenging activity of flavonoids.

The aim of study was to analyze the flavonoid composition of dietary supplements using the UHPLC-MS/MS method and to evaluate the antioxidant activity using the DPPH-UV and DPPH-UHPLC-UV methods. In the first part of the study a new method was developed for simultaneous determination of several flavonoids in dietary supplements. The amounts of flavonoids were in the range from 0.013 to 347 µg/g. In the second part of the study, the traditional DPPH-UV method and UHPLC-UV method combined with a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay were used. After application of both methods, the obtained results were similar, and the order of flavonoids depending on their antioxidant activity is the same. The effect of individual compounds on activity in combination with another flavonoid with similar or different antioxidant potentials was evaluated. The dependence of antioxidant activity on the number, type and location of the basal rings in the ring can be noted.