Anti-inflammatory effect of novel andrographolide derivatives through inhibition of NO and PGE2 production

► Introducing 15-p-Chlorobenzylidene significantly enhances anti-inflammatory effect. ► Compound 6, the most potent one, inhibits ear edema by 79.4% at 1.35 mmol/kg (ig). ► Improved activity (6) is owing to inhibition of iNOS activity and NO production. ► Compound 5 exerts the enhanced activity through inhibition of PGE2 production.