Anti-inflammatory activity of abietic acid, a diterpene isolated from Pimenta racemosa var. grissea

The anti-inflammatory activity of abietic acid, a diterpene isolated from Pimenta racemosa var. grissea (Myrtaceae), was evaluated in-vivo and in-vitro. This compound significantly inhibited rat paw oedema induced by carrageenan in a time- and dose-dependent manner, and mouse ear oedema induced by 12-O-tetradecanoylphorbol acetate, after oral or topical administration. The inhibition of myeloperoxidase enzyme showed that its topical activity was influenced by neutrophil infiltration into the inflamed tissues (ears). In addition, the effect of abietic acid on some macrophage functions was analysed in-vitro. Non-toxic concentrations of abietic acid inhibited prostaglandin E2 (PGE2) production in lipopolysaccharide-treated macrophages, whereas nitrite, tumour necrosis factor alpha and interleukin-1beta production were only weakly affected by this diterpene. PGE2 production from A23187-stimulated macrophages was only inhibited at high doses (100 microM) and it failed to modify leukotriene C4 production. These results indicate that abietic acid exerts in-vivo anti-inflammatory activity after oral or topical administration and has partial ability to prevent the production of some inflammatory mediators.