Nutrition, Phytochemicals, Antioxidants, and Cytotoxicity of Sweet Potato Leaf Tea

Abstract

Due to their nutritional loadings and the value-added aspect, fresh leaves of 5 sweet potato varieties were screened for phytochemicals and used to produce herbal teas. The teas were observed for their proximate components, antioxidants, antioxidative activity, cytotoxicity and colour parameters under brewing at 60, 80 and 100 ºC for 3, 5, 7 and 10 min. Tannins, phenolic compounds, saponins, flavonoids, phytosterols and alkaloids were contained in almost all varieties, whereas cardiac glycosides were dominant only in WP (white skin and purple flesh root) fresh leaves. Results for proximate components found that WP tea was prominent with the enrichment of crude fat (16.71 g/100 g of tea), chlorophyll b (29.41 mg/100 g of tea), cyanidin-3-glucoside (83.59 mg/100 g of tea), pelargonidin-3-glucoside (72.30 mg/100 g of tea) and tannins (1,994.81 mg TAE/100 g of tea). This was followed by RO (red skin and orange flesh root) with more protein content (0.13 g/100 g of tea). In the antioxidant test, OO (orange skin and orange flesh root) had the highest total phenolic content (1,260.92 mg GAE/100 g of tea) and offered the greatest potential of antioxidative activity (12,218.44 mg GAE/100 g of tea). No teas showed any signs of cytotoxicity (LC50 > 1,000 µg/mL). Almost all the tea was green in colour, but a yellow colour indicating lutein or its influence was also detected. In conclusion, WP, RO and OO tea were predominantly served as a low-price healthy beverage with high nutrient levels and antioxidative properties.