Isolasi dan Identifikasi Golongan Senyawa Flavonoid Serta Uji Aktivitas Antibakteri dari Kulit Batang Kelengkeng (Dimocarpus Longan Lour.)

Abstract

Flavonoid compounds have been isolated from the bark of longan (Dimocarpus longan Lour.). The isolation stage begins with maceration extraction using methanol solvent. The concentrated methanol extract was partition extracted with ethyl acetate until negative FeCl3 5%. The concentrated ethyl acetate extract was dissolved with methanol and partition extracted using n-hexane until the n-hexane layer was clear. The concentrated methanol extract was analyzed by thin layer chromatography, then separated by column chromatography with silica gel as the stationary phase and chloroform: methanol (90:10; 80:20; 70:30; 60:40) v/v as the mobile phase. Fraction 208-237 was purified by preparative thin layer chromatography with chloroform: methanol (70:30)v/v eluent producing 5 mg of yellow amorphous solid with Rf value = 0.46. Based on the UV-Vis Spectroscopy analysis using methanol solvent, it shows two absorption peaks at wavelengths (λmax) of 335 nm and 268 nm. The FT-IR spectrum shows the presence of O-H groups, C-H sp3 stretch, C=O ketone, C=C aromatic, C-H sp3 bend, C-O-C, C-H sp2 bend out-of-plane respectively at 3425.58; 2920.23; 1633.71; 1564.27; 1438.90; 1195.87, and 810,10 cm-1. The 1H-NMR spectrum shows the presence of protons H-2' and H-6', H-3' and H-5', and CH3 from 3-OCH3 Based on the results of the data analysis, the isolated compound is a flavonoid of the flavonol group. Antibacterial activity test on total flavonoids against Staphylococcus aureus and Escherichia coli bacteria showed that total flavonoids of longan bark have strong inhibition against gram-positive and gram-negative bacteria at concentrations of 25, 50, 75 mg/mL and moderate inhibition at concentrations of 10 mg/mL. This is indicated by the clear zone produced against Staphylo, coccus aureus bacteria at concentrations of 10, 25, 50, 75 mg/mL respectively of 9; 11.4; 12; 13.8 mm. While the clear zone produced against Escherichia coli bacteria at concentrations of 10, 25, 50, 75 mg/mL respectively at 9.1; 9.8; 11; 12 mm. Based on the results of the antibacterial activity test, it is known that the total flavonoid extract has antibacterial ability.