Sweet Potato Leaves as a Source of Antioxidant Phenols

Sweet potato is one of the world's most cultivated crops, and is grown all over the world, especially in Asia and the Pacific. The leaves are good forage for domestic animals, so consumption by humans is looked down upon in some places as the food of the poor. However, because some varieties of leaves are high in protein, they can be an important food source for people eating a diet based on tubers and other grains in some countries. Chinese medicine also suggests sweet potato leaves have some medicinal properties, which may be related to the phenol antioxidants in them. The objective of this study was to determine the total phenol content of sweet potato leaves. Leaves were collected from the experimental farm of Kentucky State University in the summer of 2008. The samples were separated into the purple tender leaves, the green tender leaves, the tender stems, the mature leaves and stems. Each group was homogenized and analyzed for dry matter and ash content. The acetone extracts of the samples were analyzed for total phenol content according to the Folin-Ciocalteau method. The total phenol content of the purple leaves at the tip of the vine was comparable to that of blackberries analyzed under the same conditions. The mature leaves have lower phenol content than the tender leaves and the stems contained less than half as much phenols than tender leaves. These results indicate that sweet potato leaves, especially the tender tip of the vine with the purple leaves, can be a good source of phenol antioxidants, and sweet potato greens can be used as a vegetable.