Isolasi dan Identifikasi Senyawa Golongan Flavonoida dari Biji Buah Longan (Dimocarpus longan Lour.)

Abstract

Longan fruit seeds (Dimocarpus longan Lour.) were explored for their potential as a source of flavonoid compounds through a series of isolation and structural identification techniques, namely extraction by methanol solvent (maceration method), fractionation by ethyl acetate, fractionation with n-hexane to obtain the methanol phase, then evaporated until completely evaporated. The extract was further characterized using thin layer chromatography (TLC), then fractionated through column chromatography with a stationary phase of silica gel and a mobile phase of chloroform: ethyl acetate (90:10; 80:20; 70:30; 60:40; 50:50; 40:60; 30:70; 20:80; 10:90) v/v. From the separation results, the fourth fraction was selected for further purification by preparative TLC using silica gel stationary phase and n-hexane: ethyl acetate (20:80) v/v mobile phase. The pure compound obtained was in the form of a yellow solid of 5 mg with an Rf value of 0.60. The isolated pure fraction was then characterized using a UV-Vis Spectrophotometer, the results showed the presence of 2 absorption bands, namely the first band with a wavelength of 315 nm with an absorbance of 0.2567 and the second band with a wavelength of 263 nm with an absorbance of 0.2598. Infrared spectrophotometer (FT-IR) analysis revealed the presence of functional groups O-H Stretching, C-H aliphatic Stretching, C=O ketone Stretching, C=C aromatic Stretching, C-O-H stretching, C-O-C Stretching, C-H sp2 Bending out-of-plane, with wave numbers of 3427.51 cm-1, 2924.09 cm-1, 1726.29 cm-1, 1521.84 cm-1, 1249.87 cm-1, 1109.07 cm-1, and 871.82 cm-1, respectively. Proton Nuclear Magnetic Resonance Spectrophotometer (1H-NMR) analysis showed the presence of protons H-6, H-8, H-3, H-2’, H-5’, H-6’, and OCH3. The results of the spectroscopic data confirmed that the structure of the isolated compound is a flavone.