Bioactive compounds and antioxidant activities in peeled and unpeeled sweetpotato roots of different varieties and clones in Uganda

Abstract

Rising incidences of non-communicable diseases (NCDs) in Sub-Saharan Africa (SSA) necessitates research into local functional foods, crucial in managing these conditions. This study aimed to investigate compositional changes in the bioactive compounds and antioxidant activities of peeled and unpeeled roots of Ugandan sweetpotato varieties with different flesh colours using spectrophotometric methods. Bioactive compounds and antioxidant activities, on dry weight basis were significantly higher (P<0.05) in unpeeled than peeled roots. Phenolic compounds were significantly higher (P = 0.001) in white, cream, and purple-fleshed roots (59.67–121.04 mg GAE/g) than in yellow and orange-fleshed roots (0.89–10.89 mg GAE/g). The deep orange-fleshed had the highest total carotenoids (averagely 269.82 µg/g) and the white the lowest (averagely 8.36 µg/g). Total alkaloids in the sweetpotato roots ranged between 24.05 and 233.70 µg CE/g, below the potential toxicity range of 3–10 mg/g. The anthocyanin content of purple-fleshed roots was significantly higher (15.29 mg/g; P<0.001) than the other varieties, which ranged between 0.86 and 2.44 mg/g. Principal component analysis showed a stronger relationship between phenolics, anthocyanins, tannins, and ABTS radical scavenging antioxidant activity. Vitamin C and total carotenoids were more correlated with FRAP antioxidant activity. Consumption of different sweetpotato varieties with the peels could aid in managing NCDs in SSA.