Isolasi dan Identifikasi Golongan Senyawa Flavonoida dari Kulit Batang Andromeda Jepang (Pieris Japonica (Thunb.) D.Don Ex G.Don)

Abstract

The isolation and identification of flavonoid compounds from the bark of Japanese andromeda (Pieris japonica (Thunb.) D.Don ex G.Don) had been carried out. The isolation was conducted through maceration extraction using methanol as the solvent, followed by concentration. The concentrated methanol extract was dissolved in ethyl acetate and then reconcentrated. The concentrated ethyl acetate extract was dissolved in methanol and subjected to partition extraction using n-hexane. The methanol layer was evaporated to obtain a concentrated methanol extract. This extract was analyzed using Thin Layer Chromatography (TLC), followed by column chromatography using silica gel as the stationary phase and chloroform:ethyl acetate in varying ratios (90:10; 80:20; 70:30; 60:40; 50:50; 40:60; 30:70; 20:80; 10:90 v/v) as the mobile phase. The fourth fraction from the separation was selected for purification using Preparative TLC. Silica gel was used as the stationary phase, and chloroform:ethyl acetate (30:70 v/v) as the mobile phase. The purified compound was obtained as a yellow amorphous solid weighing 6.5 mg, with an Rf value of 0.6. The isolated compound was analyzed using UV-Visible spectrophotometry, which showed one absorption band at a wavelength of 295 nm with an absorbance of 0.46722. Infrared (FT-IR) spectrophotometry analysis showed the presence of functional groups including O-H (stretching vibration), sp³ C-H (stretching), ketone C=O (stretching), aromatic C=C (stretching), sp³ C-H (bending), ether C-O (stretching), and sp² C-H (out-of-plane bending). The respective wavenumbers of these groups were 3408.22 cm⁻¹, 2927.94 cm⁻¹, 1689.64 cm⁻¹, 1604.77 cm⁻¹, 1445.84 cm⁻¹, 1267.23 cm⁻¹, and 831.32 cm⁻¹. Proton Nuclear Magnetic Resonance (¹H-NMR) spectroscopy analysis revealed the presence of protons H-8, H-6, H-2, H-3ax, H-3eq, H-2’, H-6’, H-3’, and H-5’. Spectroscopic data indicated that the isolated compound belongs to the flavonoid class, specifically a flavanone.