DCQT of 4 mL was transferred to a10 mL volumetric flask and was diluted with methanol. The mixture was extracted in an ultrasonic bath for 20 min and then the same solvent was added to compensate for the lost volume during the extraction. After centrifugation (10,000r/min, 10min), the supernatants were stored at 4 1C and filtered through a 0.22 μm microporous membrane before injecting in to the HPLC system for analysis. Fig. 1 Structures of main components in DCQT. Box-Behnken experimental design 111
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