SYNTHESIS AND EVALUATION OF ANTIOXIDANT ACTIVITY OF NOVEL FLAVONOIDS RELY ON MANNICH BASE

Abstract

We successfully synthesized  4-(3,7-diacetoxy-5-hydroxy-4-oxo-4H-chromen-2-yl)-1,2-phenylene diacetate (1) from Quercetin with acetic anhydride. Based on the Mannich reaction of 1 with various amines and formaldehyde, six novel derivatives 2-7 were synthesized and formed at 80℃ for 1-3 hours with yields of about 65- 86%. The aminomethylation occurred preferentially in the position at C-6 of the A-ring of 1. All synthesized compounds were determined by molecular structure by modern physicochemical analysis methods such as FT-IR, ¹H-NMR, ¹³C-NMR, and MS. Moreover, the synthesized compounds were evaluated for their antioxidant capacity by the standard ABTS method, showing that all compounds have the antioxidant capacity, of which the best compounds were 3 (IC₅₀ 64.02±0.15 µM), 5 (IC₅₀ 164.74±0.14 µM) and 7 (IC₅₀ 167.40±0.11 µM) 1.4-3.4 times higher than Trolox standard (IC₅₀ 221.31±0.17 µM). These are potential compounds for antioxidant applications.