Phenolic profiling and antioxidant evaluation of extracts from Southern African indigenous fruits byproducts

The call to build climate-resilient food systems in Africa has revived interest in indigenous fruits, which, however, remain under-researched. In this study, the phenolic content and antioxidant profiles of seed and pulp of ethanolic extracts from eight Southern African indigenous fruits were evaluated using UPLC-ESI-Q-TOF/MS and four antioxidant assays. Total phenols and hydroxycinnamic acids were highest in Dovyalis caffra (Kei apple) seed (5084.5 and 3403.83 mg/kg). Flavonoids were most abundant in Colpoon compressum (Colpoon) seed (1127.23 mg/kg), while hydrolysable tannins were highest in Syzygium guineense (Water pear) seed (666.13 mg/kg). Proanthocyanidins were abundant in Harpephyllum caffrum (Wild plum) pulp while anthocyanins were highest in Olea africana (Wild olive) pulp. Hierarchical clustering heatmap analysis showed similar concentration and diversity in the composition of reported compounds. Syzygium guineense seed had the lowest DPPH values. ORAC values were highest in O. africana pulp while H. caffrum pulp had the highest FRAP values and lipoxygenase inhibition capacity. In conclusion, the study revealed a diverse profile of phenolics in indigenous fruits extracts, to which their bioactivity is attributed. Specifically, H. caffrum pulp and S. guineense seed have potential as natural sources of phenolic antioxidants for food application.