Zanzibar yam (Dioscorea sansibarensis Pax) isolates exhibit cyclooxygenase enzyme and lipid peroxidation inhibitory activities

Several phenanthrenes (1-5), phenolics (6-8) and steroidal sapogenins (9-11) were isolated for the first time from the aqueous and methanolic extracts of Dioscorea sansibarensis Pax yam collected from Tanzania. Chemical structures of all the isolates (1-11) were determined by using 1D and 2D nuclear magnetic resonance spectral methods. All pure isolates were evaluated for anti-inflammatory activity using in vitro cyclooxygenase enzyme (COX-1 and -2) inhibitory assays. Among the isolates tested, phenanthrenes 3-5 showed the highest COX-1 and -2 enzyme inhibitory activity whereas phenolics (6-8) and steroidal sapogenins (9-11) exhibited moderate inhibition when compared to non-steroidal anti-inflammatory drugs aspirin, ibuprofen and naproxen. Compounds 6-11 were evaluated for antioxidant activity using lipid peroxidation inhibitory (LPO) assay for the first time and exhibited moderate LPO inhibition.