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Identification of 5,6,8-Trihydroxy-7-methoxy-2-(4-methoxyphenyl)-4H-chromen-4-one with antimicrobial activity from Dodonaea viscosa var. angustifolia

Ngabaza, T., Johnson, M.M., Moeno, S., Patel, M.
South African journal of botany 2017 v.112 pp. 48-53
Dodonaea viscosa, Fourier transform infrared spectroscopy, antimicrobial properties, cytotoxicity, fractionation, fungi, gas chromatography-mass spectrometry, humans, inhibitory concentration 50, kidneys, leaves, methanol, molecular weight, nuclear magnetic resonance spectroscopy, pathogens
The aim of this study was to isolate a chemical constituent from Dodonaea viscosa var. angustifolia, investigate its effect on a range of pathogens and identify the major beneficial compound.Leaves were dried, milled and a methanol crude extract was prepared. Fractions were obtained using column chromatography. Antimicrobial activity of these fractions against various microorganisms was determined using a microdilution technique. The most effective fraction was purified by flash chromatography, and characterized and identified using GC–MS, NMR, UV–Vis and FT-IR. Cytotoxicity tests were carried out on human embryonic kidney cells.Six fractions (F1–F6) were separated. Fraction 5 had the most antimicrobial activity (MIC 0.39mg/ml). On further fractionation of Fraction 5, two subfractions (F5.1 and F5.2) were obtained. F5.1 showed better antimicrobial activity (0.2mg/ml) compared to the F5.2. F5.1 was identified as new compound, 5,6,8-Trihydroxy-7,4-dimethoxyflavone (5,6,8-Trihydroxy-7-methoxy-2-(4-methoxyphenyl)-4H-chromen-4-one) with a molecular formula C17H14O and molecular weight 330.28amu. The concentrations of newly isolated, elucidated and identified compound that inhibited cells by 50% (IC50) was 0.03mg/ml.In conclusion, DVA leaves contain 5,6,8-Trihydroxy-7,4-dimethoxyflavone which has antimicrobial activities against common pathogens and unicellular fungi and it proved to be safe. Therefore it has the potential to be developed into a therapeutic agent.