Determination of total polyphenol, saponin contents, antioxidant and antibacterial activities of Melastoma malabathricum leaves by liquid-liquid extraction

Abstract

The present study aims to investigate the total polyphenol and saponin contents, antioxidant and antibacterial activities of Melastoma malabathricum leaves extracts. These fractions were carried out using n-hexane, n-hexane:ethyl acetate (ratio 1:1), ethyl acetate and methanol solvents. The crude extract (CE) exhibited the highest amount of total polyphenol content by using the Folin-Ciocalteu assay. The n-hexane fraction (F1) showed the highest total saponin content which was determined by Vanillin/H2SO4 method. The antioxidant activity of extracts was evaluated by using three different methods including DPPH radical scavenging assay, hydrogen peroxide assay (H2O2) and reducing power assay (Fe3+). The results showed that the activity of the methanol fraction (F4) against DPPH was the strongest, the CE extract was the highest reducing power and the ethyl acetate fraction (F3) illustrated the strongest antioxidant capacity through H2O2 assay. Furthermore, all extracts were also tested for the antibacterial activity by agar well diffusion method at a concentration of 100 mg/mL. F4 showed the highest activity against Escherichia coli and Staphylococcus aureus, while there were no significant differences among all extracts when testing with Lactobacillus acidophilus. These findings provide important evidence that a correlation between the polyphenol content and antioxidant capacity and antibacterial activity. Whereas, the saponin content was no contribution to antioxidant and antibacterial abilities.