Evaluation of phenolics and bioactivities of Camellia quephongensis leaf extracts as affected by various extraction solvents

Abstract

Camellia quephongensis is an endemic Theaceae species from Central Vietnam. In the present study, phenolics in extracts from leaves of this plant species were quantified. Additionally, free radical scavenging activities, α-amylase and albumin denaturation inhibitory effects of the extracts were evaluated. Catechins were found at significantly higher concentrations in the methanolic and ethanolic extracts compared to the other extracts. The ethanolic extract showed the most potent radical scavenging activities determined by ABTS and DPPH assays, with IC50 values of 57.88 ± 1.89 and 47.87 ± 0.16 μg/mL, respectively. Furthermore, the capacity of this extract to counteract ABTS radicals was comparable with that of ascorbic acid. The ethyl acetate extract exerted the strongest α-amylase inhibitory activity (IC50 = 985.79 ± 16.37 μg/mL). The aqueous methanolic extract with the lowest IC50 value (57.56 ± 3.28 μg/mL) exhibited the highest protective effect on albumin against denaturation, and this was even higher than that of diclofenac. The correlation analysis demonstrated that catechins and ferulic acid may play important roles in radical scavenging activities while gallic acid, chlorogenic acid, and rutin could contribute to albumin denaturation inhibitory effects of the extracts. The findings of the study improve our understanding of bioactive phenolics and potential health benefits associated with C. quephongensis leaves.