Optimization of Conditions of Extraction of Flavonoids from Wormwood with the Algorithms of Response Surface Analysis and Single Factor Analysis

Molecular fluorescence photometry was applied to the determination of flavonoids in test solutions obtained from the study on optimization of conditions of extraction of flavonoids from wormwood, and the optimum conditions of the extraction were determined on the base of the data of rate of extraction found. 3 factors, i.e., volume fraction of the ethanol solution, time for the ultrasonic extraction and ratio of mass of wormwood sample to volume of the ethanol solution used for extraction, were studied. As found by single factor analysis, values of the 3 factors were obtained as follows:① volume fraction of ethanol solution:50%; ② time for ultrosonic extraction:40 min and ③ ratio of mass of wormwood sample to volume of 50% C₂H₅OH solution:1.0 g to 15 mL. Rate of extraction attaining to a value of 1.07% was obtained under this condition. The 3 factors were taken as the factors to be optimized furthermore by the response surface analysis using the Design Expert 8.0 software by testing at factorial design of 3 factors and 3 levels. The optimum values of the 3 factors found by this method were as follows:① volume fraction of ethanol solution:49.96%; ② time of ultrosonic extraction:30 min and ③ ratio of mass of wormwood sample to volume of the ethanol solution:0.79 g to 15 mL. Rate of extraction found under this condition was found to be 1.09%. To verify the above optimized extraction condition, 3 portions (0.790 0 g each) of the powdered wormwood sample were taken and extracted under the optimized condition. The ethanolic mixture of solution and some undissolved was filtered and centrifuged. 1 mL of the supernatant was taken from each of the extract of the samples (the exact volume of each of the aliquot was determined from the estimated amount of flavonoids present in the sample solutions to have the mass concentration of the flavonoids in the aliquot happened to drop in the linearity range of the standard curve between 0.006 to 0.018 g·L^-1) and proceeded as follows:2.38 mL of 5.3 g·L^-1 Al(NO₃)₃ solution and 0.90 mL of pH 5.6 acetate buffer solution were added separately and the total volumes of the solutions were made up to 10.0 mL. After staying for completion of the fluorescent complexation between the flavonoids and Al(Ⅲ) ion values of intensity of the emission fluorescence were measured. It was shown that the average rate of extraction found was 1.08%, which gave a relative error of -0.92% with the theretically predicted value.