In this study, the effects of diffe

In this study, the effects of different concentrations of ethanol (30–100%, v/v) on extraction efficiency were determined. As shown in Fig. 1d, the yield of flavonoids increased from 10.68 ± 0.17 to 15.87 ± 0.29 mg/g when the concentrations of aqueous ethanol varied from 50% to 70%. These results suggest that the addition of some amount of water can improve the extraction efficiency. This may be because water has a potential of increasing the polarity of aqueous ethanol. Another possible reason may be due to the increase in swelling of plant material by water, which increased the contact surface area between the plant matrix and the solvent (Hemwimon, Pavasant, & Shotripruk, 2007). However, the yield of total flavonoids decreased rapidly when ethanol concentration was above 70%. In other words, the highest extraction efficiency was achieved at 70% ethanol. Similar results were reported by Zhang et al. (2013) in the extraction of flavonoids from cultivated E. sagittatum. Therefore, 70% ethanol was selected as optimal solvent.