Comparison of the total phenolic content and antioxidant and antibacterial activities of different fractions obtained from selected plant leaves native to Viet Nam

In this study, five types of plant extracts in Vietnam were selected to compare phenolic content, antioxidant and antibacterial activities, respectively Gymnanthemum amygdalinum (bitter leaf), Piper betle (betel), Pseuderanthemum bracteatum (Imlay), Piper sarmentosum (kaduk), and Paederia tomentosa (stinkvine). Five types of leaves were fractionally extracted with n-hexane (HE), ethyl acetate (EA) and water (W) solvents. The antioxidant activity was compared based on free radical scavenging capacity (DPPH, ABTS), iron reducing capacity (FRAP) and iron chelation capacity (FIC). At the same time, the total phenolic content (TPC) was also compared by the Folin-Ciocalteau method. The results demonstrate antioxidant activity (DPPH), the EA fraction of betel leaf was the best, followed by four extracts of bitter leaf > kaduk > Imlay > stinkvine. Similarly, the EA fraction of betel leaf also showed the highest FRAP and ABTS iron-reducing activity. A correlation between phenolic content and antioxidant activities of leaf extracts was also investigated. Regarding antibacterial activity, betel leaf in all fractions showed the highest antibacterial activity against most gram (+) and gram (-) organisms through diffuse on agar plate test. Meanwhile, bitter leaf showed the lowest antibacterial activity in both EA and W fractions.