Abstract

Cyclooxygenase 2 (COX-2) is involved in the production of prostaglandins that sustain the inflammatory process. Inflammatory cells release a number of reactive species. Furthermore, reactive oxygen species can initiate intracellular signaling cascades and enhance the expression of pro-inflammatory genes. The objective was to study the cyclooxygenase and protein denaturation inhibition and antioxidant activity of ten extracts from five plants. Cyclooxygenases inhibitory activity of the extracts was measured using the Cayman Kit method and the protein denaturation inhibitory activity using the bovine serum albumin. Ferric reducing antioxidant power and hydrogen peroxide scavenging activity were used to evaluate the antioxidant capacity of aqueous and hydroethanolic extracts. COX-2 inhibition was more important with the hydroethanolic extract of X. americana (IC50 = 11.13 ± 1.24 µg/ml) and T. macroptera (IC50 = 12.79 ± 0.56 µg/ml). COX-1 was strongly inhibited with the hydroethanolic extract of S. senegalensis. The hydroethanolic extracts of C. tinctorium and X. americana showed the strongest inhibitory activities of protein denaturation with 86.61 ± 1.22% and 84.5 ± 0.56% respectively. The greatest effects on iron reduction were observed with the hydroethanolic extracts of X. americana (R2 = 0.996; IC50 = 29 µg/ml) and T. macropteria (R2 = 0.990; IC50 = 35.46 µg/ml). The hydrogen peroxide scavenging activity of the extracts varied from 39.31 ± 3.6 to 77.37 ± 2.16 µg/ml. The present study concluded to an important antioxidant activity, protein denaturation and COX-2 inhibitory activities of the hydroethanolic extracts of X. americana, T. macroptera and C. tinctorium. Further studies are needed to confirm the anti-inflammatory effect of these extracts in vivo.

Key words: X. Americana, T. macroptera, cyclooxygenases, antioxidant, protein denaturation.