This study was conducted to assess the anti-inflammatory effect of a novel synthesized phenanthridine alkaloid (PHE-4i) and to examine the possible involvement of hydrogen sulfide (H₂S) in anti-inflammatory mechanism. The synthesized phenanthridine derivative PHE-4i (2, 5, and 10 mg/kg) was administered intraperitoneally to rats. One hour following treatment, inflammation was induced by intraplantar injection of carrageenan (1 %), in the hind paw. Paw volume as the index of inflammation was measured before and after carrageenan injection. Neutrophil sequestration into the hind paw was quantified by measuring tissue myeloperoxidase (MPO) activity and was compared for the inhibition of H₂S production. Pretreatment with PHE-4i significantly reduced carrageenan-induced hind paw weight, MPO activity, leukocyte infiltration, and H₂S production in a dose-dependent manner (p < 0.001). These results indicate that the anti-inflammatory effect of PHE-4i on carrageenan-induced rat paw oedema could be via the inhibition of the gaseous mediator H₂S.