An Evaluation of Phenolic Compounds, Carotenoids, and Antioxidant Properties in Leaves of South African Cultivars, Peruvian 199062.1 and USA's Beauregard

In this study, leaves of sweet potato cultivars from South Africa (Ndou, Bophelo, Monate, and Blesbok), Beauregard, a sweet potato cultivar from the USA, and a Peruvian cultivar 199062. 1 were analyzed using UPLC/QTOF/MS and chemometrics, with the aim of characterizing the locally developed sweet potato cultivars and comparing them with already well-known established varieties on the market. A set of 13 phenolic compounds was identified. A partial least squares discriminant analysis, a hierarchical cluster analysis, and variables importance in projection were used to successfully distinguish sweet potato varieties based on their distinct metabolites. Caffeic acid enabled to distinguish Cluster 1 leaves of varieties (Beauregard and Ndou) from Cluster 2 (199062.1, Bophelo, Monate, and Blesbok). The leaves of Bophelo contained the highest concentrations of rutin, quercetin 3-O-galactoside, 3-caffeoylquinic acid (3-CQA), (5-CQA), 1,3 dicaffeoylquinic acid (1,3-diCQA), 1,4-diCQA, and 3,5-diCQA. Furthermore, Bophelo leaves showed the highest antioxidant activities (FRAP 19.69 mM TEACg(-1) and IC50 values of (3.51 and 3.43 mg ml(-1)) for DPPH and ABTS, respectively, compared to the other varieties. Leaves of Blesbok contained the highest levels of beta-carotene (10.27 mg kg(-1)) and zeaxanthin (5.02 mg kg(-1)) on a dry weight basis compared to all other varieties. This study demonstrated that the leaves of local cultivars Bophelo and Blesbok have the potential to become functional ingredients for food processing.

Automated summary

Using UPLC/QTOF/MS and chemometrics, this study characterized sweet potato cultivars from South Africa, the USA, and Peru, identifying 13 phenolic compounds. Different varieties were successfully distinguished based on their distinct metabolites, with Bophelo and Blesbok showing the highest antioxidant activities and levels of specific compounds. The leaves of these local cultivars have the potential to become functional ingredients for food processing.