24 derivatives (5a-x) derived from natural pyranochalcones (I and II) were designed and evaluated for their inhibitory potency on the production of nitric oxide (NO) in LPS-stimulated RAW264.7 cells. Among them, four compounds (5b, 5d, 5f, and 5h) exhibited more potent inhibitory effects on iNOS activity and iNOS-mediated NO production than a positive control indomethacin. Furthermore, 5b could significantly suppress the progression of carrageenan-induced hind paw edema compared to indomethacin at a dosage of 10 mg/kg/day, and dose-dependently ameliorated the development of adjuvant-induced arthritis (AIA) validated by arthritic scores and H&E staining of joints. In addition, docking study confirmed that 5b was an iNOS inhibitor with binding to the active site of murine iNOS.