Microwave-assisted extraction of phenol and flavonoid compounds….doc

M.Gharekhani and et alPAGE PAGE 14Microwave- assisted extraction of phenolic and flavonoid compounds from Eucalyptus camaldulensis Dehn leaves as compared with ultrasound-assisted extraction AbstractBackground: Traditional techniques usually require longer extraction time thus running a severe risk of thermal degradation for most of the phyto-constituents. Novel extraction methods including microwave assisted extraction (MAE) have drawn significant research attention in the last decade.Objective: The purpose of the present research was to develop a MAE method and compare it with UAE and traditional extraction methods for extraction of total phenolic and flavonoid compounds from eucalyptus leaves.Methods: A household microwave oven (Samsung, Korea) was modified in our laboratory. Experiments were carried out to determine the effect of type of solvents, ethanol concentration, MAE time, liquid/solid ratio and pre-leaching time before on extraction efficiency of phenolic and flavonoid compounds.Results: Among the solvents tested, 50% ethanol extracted the highest phenolic and flavonoid contents from eucalyptus leaves. The extraction of phenolic and flavonoid compounds with MAE for 5 min was equivalent with ultrasound-assisted extraction (UAE) (60 min) and traditional extraction (24 h) methods. From the point of extraction time, the time of extraction at room temperature and UAE was about 12, 288-folds of time of extraction with MAE, respectivelyConclusion: Due to the considerable saving in time, MAE was more effective than the traditional and UAE methods.Key words: Microwave-assisted extraction, Eucalyptus leaves, Total phenolic compounds, Total flavonoid compound.IntroductionAntioxidants are compounds that inhibit or delay the oxidation of other molecules by inhibiting the initiation or propagation steps in the of oxidization chain reactions. Antioxidants are either natural or synthetic. Synthetic antioxidants have phenolic structures of various degrees of alkyl su