| Allium tuberosum, a healthy vegetable recorded in the ancient literatures of traditional Chinese medicine, has good potential for protection against kidney diseases. The main results obtained in this study are shown as the follows:(1) The screening of active compounds from A. tuberosum Different extracts including alcohol extracts (AS1), water extracts (WS), alcohol-soluble fraction of water extracts (AS2) and crude polysaccharide (ATPS) were prepared from A. tuberosum. The chronic renal failure (CRF) in Kunming mice was induced by feeding with adenine (0.2%, w/w) for up to 5 weeks. According to mice body weights, biochemical and histopathological studies in plasma and renal homogenates from each groups, the active compounds of A. tuberosum were screened. Results showed that the WS and ATPS could significantly decrease the serum urea nitrogen (BUN) and creatinine (Scr), improve the renal superoxide dismutase (SOD) activity and glutathione (GSH) contents, and reduce the renal malondialdehyde (MDA) contents. Moreover, compared to the model group, the mRNA expressions of IL-1β, IL-6, TNF-α and TGF-β1 were alleviated by WS and ATPS treatment while that of IL-10 was enhanced. In comparison with the functions of WS and ATPS, AS1 and AS2 did not exhibit the protective effects on kidney disease induced by adenine.(2) The establishment of dynamic model for ultrasound-assisted extraction (UAE) of polysaccharide from A. tuberosum (ATPS) According to the Fick’s second law, the dynamic equation for UAE of ATPS was established where the ultrasound-induced degradation of polysaccharides was considered. In order to obtain the key parameters and verify the accuracy of dynamic model, the effects of ultrasonic power, extraction temperature, solid-liquid ratio and ultrasonic time on ATPS yields were investigated. Results indicated that the dynamic equation y=y∞/(1+kD×t) × [1-exp(-k×t)]+y0/(1+kD×t)× exp(-k×t) could well simulated the extraction process of ATPS by UAE method. In this model, the yo was a constant value of 0.46%, y∞, kD and k was dynamic parameters associated with extraction temperature, ultrasonic power, solid-liquid ratio and extraction time. According to this dynamic model, an optimal condition for ATPS extraction by UAE was obtained and characterized as solid-liquid ratio (1:30), extraction temperature (37℃), ultrasonic power (458 w) and ultrasonic time (30 min). Under this extraction condition, the expected highest ATPS yield can reach 3.73%. To verify this prediction, verification experiments were further carried out using this optimal condition for three times. Results showed that there is only 1.89% error between the experimental value and predicted value. Moreover, the UAE method exhibited much higher extraction efficiency of ATPS than that of conventional water extraction (CWE) method. However, too high ultrasonic power or too long ultrasonic time can result in the degradation of ATPS.(3) Determination of the main objective fractions of ATPS extracted by UAE method The ATPS extracted by UAE and CWE were precipitated using 40%,60% and 80% ethanol in turn. According to the differences among these precipitates, we found that UAE significantly increased the fraction of ATPS precipitated with 60%ethanol. In addition, the contents of polysaccharide with a molecular weight of 5.38×106 Da in this fraction extracted by UAE method were enhanced by 134% when compared to that of CWE method. These results suggested that the polysaccharide with molecular weight at 5.38×106 Da was the main target of UAE. |
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