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

Abstract

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 β-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.