Study On Radix Pueraria Isoflavones Extraction By Fermentation And Its Antioxidation

Radix pueraria, which was the root of Pueraria lobata(Wild.) Ohwi, can be used as food and traditional Chinese herbal. It contains plenty of starch, cellulose, isoflavones and minerals. Radix pueraria isoflavones (RPI) were a series of estrogen existed in plant. RPI can play a predominant role as antiaging, anticancer, antioxidant compound, and so on. Puerarin accounts for more than 50% of RPI, and always be regarded as a main index to evaluate the quality of Radix pueraria. In this study, HPLC was applied to determine the content of puerarin in fermentative supernatant, based on which the most suitable microorganism was selected out. The components of culture and fermentative conditions were optimized. Then both purification techniques and antioxidation ability of RPI were detected. The main results were concluded as follows:1 HPLC was proved to be a fairly good method to determine puerarin in fermentation sample, and the stability, accuracy, and recovery were all within acceptable levels. The optimum detection rang of puerarin was 40～200μg/mL with R2 0.9996.2 Setting puerarin yield as the main indicator, a mixture microorganisms of Rhizopus oryzae and Saccharomyces cerevisiae were proved to be suitable for extracting of RPI. Plackett-Burman design was applied to select the factors that have significant positive effects on RPI yield, and they were liquid-solid ratio, peptone, and KH2PO4. Then the optimum levels of them were obtained by response surface experiments. The RPI and puerarin yield can reach to 31.98 and 16.18 mg/g-DW with the liquid-solid ratio 30:1, peptone 8.49 g/L, and KH2PO4 6.89 g/L, respectively.3 Saccharification temperature, initial pH, and capacity volume were optimized by Box-behnken design. Results showed that the optimum fermentative conditions in this study were initial pH 6.88, volume 80 mL, saccharification temperature 36.2℃, subsequent-fermentation temperature 28℃, ratio of inoculum size of R. oryza and S. cerevisia 6%:6%. Under these conditions, the RPI and puerarin yield can reach to 40.29 and 18.36 mg/g-DW, respectively. 4 The absorption and desorption ability of different kinds of macroporous resins were investigated, and NKA-II was selected as the optimal one for its excellent performance. The results showed that the optimum conditions to purify the fermentative RPI were as follows: absorption time 8 h, absorption temperature 25℃, and desorbent 60% ethanol water solution. Comparing RPI obtained from different extraction methods, fermentative RPI exhibited the most remarkable activities in scavenging DPPH and superoxide radicals, while the hydroxyl radical scavenging activity was relatively lower than the others.