Abstract: This study investigated the effect of foliar versus soil application of selenium on the selenium content of sweet potato leaves and the antioxidant activity of sweet potato leaf proteins. The results showed that both foliar and soil applications of selenium could increase the protein-bound selenium content of sweet potato leaves. The protein-bound selenium contents of the foliar and soil selenium treatment groups at 1.6 mg/mL concentration were 20.10 and 1.68 mg/g, respectively. Selenium enrichment could improve the antioxidant activity of sweet potato leaf proteins. The superoxide anion free radical scavenging capacity of sweet potato leaf proteins was increased by 19.17% with foliar selenium enrichment. According to correlation analysis, the total selenium content and protein-bound selenium content of sweet potato leaves significantly affected the antioxidant activity, and the total phenolic and total flavonoid contents also affected the antioxidant activity. In conclusion, compared with soil selenium application, foliar selenium application was better in increasing the protein-bound selenium content of sweet potato leaves.

Key words: selenium enrichment; sweet potato leaf proteins; antioxidant activity