Inhibitory Effects of 6-alkoxycoumarin and 7-alkoxycoumarin Derivatives on Lipopolysaccharide/interferon γ-stimulated Nitric Oxide Production in RAW264 Cells

Coumarin and its derivatives are well known for their anti-inflammatory and anti-oxidative effects. In this study, we synthesized 32 coumarin derivatives from commercially available 6-hydroxycoumarin (6HC) and 7-hydroxycoumarin (7HC) and examined their effects on lipopolysaccharide/interferon γ (LPS/IFNγ)-stimulated nitric oxide (NO) production in murine macrophage RAW264 cells. Among these derivatives, 6HC-8 (6-(3-phenylpropoxy)coumarin), 6HC-14 (6-(2-octynyloxy)coumarin), 7HC-14 (7-(2-octynyloxy)coumarin), and 7HC-16 (7-(3,5-dimethoxybenzyloxy)coumarin) markedly suppressed NO production at low concentration (25 µM). These synthesized coumarin derivatives also markedly inhibited inducible NO synthase (iNOS) protein and mRNA expression, as assessed by western blotting and quantitative real time-polymerase chain reaction (RT-PCR).