Phenanthrenes in Chinese Yam Peel Exhibit Antiinflammatory Activity, as Shown by Strong in Vitro Cyclooxygenase Enzyme Inhibition.

Chinese yam (Dioscorea opposita), peeled or whole, is a popular food item that is considered to be healthy. Often, the yam is peeled before cooking. However, it is also consumed with peel. Therefore, in this study, the peel of this yam was extracted sequentially with n-hexane, ethyl acetate and methanol, and studied for its health-benefits, using in vitro bioassays. Bioactivity-guided purifications of extracts of the peel afforded phenanthrenes (1-4), as characterized- by spectroscopic methods. Phenanthrene I is a novel analogue. The extracts and isolates were tested for antiinflammatory activity using cyclooxygenase enzyme (COX- I and -2) inhibitory assays. All phenanthrenes isolated from the yam peel showed higher inhibition of COX enzymes than the over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) aspirin, ibuprofen and naproxen.