The crude ethanol extract of Piper betle leaf is reported to possess anti- inflammatory activity which has been suggested to be mediated by allylpyrocatechol (APC). In the present study, we have demonstrated the anti-inflammatory effects of APC (10 mg/kg, p.o.) in an animal model of inflammation. To investigate the mechanism(s) of this anti-inflammatory activity, we examined its effects on the lipopolysaccaride (LPS)-induced production of NO and PGE₂ in a murine macrophage cell line, RAW 264.7. APC inhibited production of NO and PGE₂ in a dose dependent manner as also decreased mRNA expression of iNOS, COX-2, IL-12p40 and TNF-alpha. Since nuclear factor-κB (NF-κB) appears to play a central role in transcriptional regulation of these proteins, we investigated the effects of APC on this transcription factor. APC inhibited LPS induced nuclear factor-kappaB (NF-κB) activation, by preventing degradation of the inhibitor kappaB (IκB). Taken together, our data indicates that APC targets the inflammatory response of macrophages via inhibition of iNOS, COX-2 and IL-12 p40 through down regulation of the NF-κB pathway, indicating that APC may have therapeutic potential in inflammation associated disorders.