Antioxidant, anti‐inflammatory, and enzyme inhibitory activity of natural plant flavonoids and their synthesized derivatives

The synthesized flavonoid derivatives were examined for their antioxidant, anti-inflammatory, xanthine oxidase (XO), urease inhibitory activity, and cytotoxicity. Except few, all the flavonoids under this study showed significant antioxidant activity (45.6%-85.5%, 32.6%-70.6%, and 24.9%-65.5% inhibition by DPPH, ferric reducing/antioxidant power, and oxygen radical absorption capacity assays) with promising TNF-α inhibitory activity (42%-73% at 10 μM) and IL-6 inhibitory activity (54%-81% at 10 μM) compared with that of control dexamethasone. The flavonoids luteolin, apigenin, diosmetin, chrysin, O3Ꞌ , O⁷ -dihexyl diosmetin, O4Ꞌ , O⁷ -dihexyl apigenin, and O⁷ -hexyl chrysin, showed an inhibition with IC₅₀ values (4.5-8.1 μg/mL), more than allopurinol (8.5 μg/mL) at 5 μM against XO and showing more than 50% inhibition at a final concentration (5 mM) with an IC₅₀ value of ranging from 4.8 to 7.2 (μg/mL) in comparison with the positive control thiourea (5.8 μg/mL) for urease inhibition. Thus, the flavonoid derivatives may be considered as potential antioxidant and antigout agents.