Solvent Selection in Extraction of Essential Oil and Bioactive Compounds from Polygonum minus

Abstract

This preliminary study evaluated the biological activity of Polygonum minus (kesum) using two bioassays: antioxidant and antibacterial assay. P. minus was extracted using maceration method (solvent extraction) to study the effect of solvent type and concentration in biological activity of P. minus. Seven solvents (water, 50% (v/v) methanol, 50% (v/v) ethanol, 70% (v/v) methanol, 70% (v/v) ethanol, methanol and ethanol) were used in order to select the best solvent to be used in supercritical fluid extraction (SFE). The antioxidant capacity was evaluated using four different assays: Total Phenolic content assay (TP), Total Flavonoid content assay (TF), Ferric Reducing/antioxidant Power (FRAP) assay and free radical-scavenging capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Seventy percent methanol extract showed the highest polyphenol and flavonoid content. The highest TP and TF were from 70% methanol extract (11.3±0.06 mg gallic acid equivalents/g extract (mg GAE g-1) and 22.5±0.07 mg catechin equivalents/g extract (mg CAE g-1 extract, respectively). Seventy percent methanol extract also showed the highest FRAP value and percentage of DPPH radical inhibition which were 377.6±5.40 μMol Fe (II)/g sample and 80.3±0.10%. The high antioxidant capacity was significantly correlated with high TP/TF content. Agar-well diffusion method was used to investigate the antibacterial activity where result showed that 70% methanol extract exhibited the largest inhibition zone against Staphylococus aureus (Gram+), 16.2±0.30 mm in diameter.