Synthesis, characterization and antioxidant activity of quercetin derivatives.

A series of quercetin derivatives were synthesized via Williamson etherification, Steglich esterification or Koenigs–Knorr glycosylation reaction at 3 and 7 position hydroxyl groups selectively. The structures of the synthesized compounds were characterized and identified by IR, 1H NMR, 13C NMR and HR-MS. The antioxidant capacity of synthesized compounds was determined by total antioxidant capacity assay kit with ABTS method (T-AOC Assay Kit). The results revealed that the compounds Qr-5a, Qr-5b, Qr-5c, Qr-5d and Qr-12 manifested significant antioxidant activities comparing to that of the positive control rutin (TEAC = 3.28), among which the antioxidant capacity of Qr-12 was the strongest, and the TEAC value was 5.19. [ABSTRACT FROM AUTHOR]