Evaluation ofin VitroAnti-inflammatory and Antioxidant Activity of Selected Zimbabwean Plant Extracts

The in vitro anti-inflammatory and antioxidant activities of Zimbabwean medicinal plant extracts were investigated by COX-1 and COX-2 enzyme inhibitory activity, the erythrocyte membrane stabilization, and albumin denaturation inhibition assays; free-radical scavenging activity of the plant extracts was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tetramethoxy azobismethylene quinone (TMAMQ) radical scavenging assays. Combretum zeyheri, C. molle, and Parinari curatellifolia inhibited COX-2, inhibiting COX-1 the least with inhibitions of 42, 68, and 77%, respectively, for COX-2. C. platypetalum selectively inhibited COX-2 by 85% and COX-1 inhibition by 42%. IC50 of C. platypetalum and indomethacin for COX-2 were 571 and 414 µg.mL–1, respectively. C. platypetalum, C. molle, and Brachystegia boehmii stabilized the erythrocyte membrane and inhibited the precipitation of proteins in vitro. Plant extracts that inhibited the COX enzymes were tested for antioxidant activity using the DPPH and the TMAMQ free-radical scavenging assays. P. curatellifolia extract showed potent antioxidant activity in both assays with 100% of the radicals quenched at 16 and 18 µg.mL–1, respectively.