Effect of Acacia Species on Adjuvant-induced Arthritis in Rats

Acacia species (Mimosaceae) are used in Sudanese traditional medicine to treat various inflammatory diseases. The present study was designed to investigate the effect of dichloromethane (DCM) and 90% methanol extracts of bark and leaves of three Acacia species on cycoloxygenase-1 (COX-1) and -2 (COX-2) enzymes. The investigated species were: A. nilotica subsp. tomentosa, A. nubica and A. senegal subsp. senegal. The results showed that DCM bark extracts of all species showed high COX-2 selective inhibition (IC₅₀ values of 0.45, 37 and 17.3 μg/mL) compared to COX-1 inhibition (IC₅₀ values of 206.3, >250, >250 μg/mL) respectively. The DCM bark extracts of the three species were evaluated further in vivo in rats with adjuvant-induced arthritis. DCM bark extracts of A. senegal significantly reduced the edema when administered at a dose of 300 mg/kg. The extract did not cause lesions in the gastrointestinal mucosa compared to indomethacin which caused severe lesions in the small intestine (ulcer index = 194.3±2.7 mm²). On the other hand, DCM bark extracts of A. nubica and A. nilotica were not active in in vivo assay. The results suggest that DCM bark extracts of A. senegal subsp. senegal may be useful in the treatment of rheumatoid arthritis.