| Fig tree(Ficus carica L.)is a kind of fruit tree of Moraceae.It has been cultivated and applicated widely in China with long history.Leaves of fig tree are rich in natural active substances.It can improve immune activity,antibacterial,anti-tumor and so on.However,leaves of fig tree containing a large number of bioactive components have not been fully utilized at present.After fruit harvest in spring and autumn,leaves of fig tree are often discarded as agricultural waste,resulting in a waste of resources.Therefore,it is necessary to develop and utilize leaves of fig tree resources reasonably and maximize the utilization value of fig trees.In this study,the method of extracting polysaccharides(FCPS)in leaves of fig tree has been established and the hypoglycemic effect of polysaccharides were investigated.1.Established a freeze-thaw synergistic ultrasonic-microwave extraction method(FTSUME)for the extraction of FCPS.The factors affecting the extraction of FCPS,liquid-solid ratio,microwave power and extraction time,were optimized RSM.The optimum extraction parameters were obtained by model fitting:freeze-thaw pretreatment for 3 times,liquid-material ratio of 28 g/mL,extraction time 12 min and power of microwave 520 W.The results showed that the yield of FCPS was 5.13±0.62%under the optimal extraction parameters.By comparing the traditional method,the yield of FCPS by freeze-thaw assisted ultrasonic-microwave synergistic extraction method was 1.13-fold and 1.49-fold higher than other methods,respectively.The results showed that this method has the advantages of short extraction time and high yield.2.Purification and molecular weight determination of FCPS.The protein in the crude polysaccharides was removed by Sevag method,and the purity of FCPS was increased from 31.16%to 54.80%,and the retention rate of FCPS was 66.10%.The pigment and water-soluble small molecule impurities were removed by AB-8 macroporous adsorption resin,and the retention rate of FCPS were calculated to be 83.22%,respectively.Dialysis removes small molecular impurities.The retention rate of FCPS purified by this step was 76.47%,and the purity after dialysis was 73.52%.FCPS was isolated and purified by DEAE-52 cellulose column chromatography and Sephadex G-75 column chromatography,and the purity of FCPS reached 90.52%and a recovery rate of 88.45%.Based on raw materials,the final yield of FCPS was 2.49%.The molecular weight of FCPS is 6.59 × 105 Da.The composition and percentage of FCPS monosaccharides detected by HPLC were Gal 40.1%,Ara 25.1%,Glc 11.4%,GalA 1.9%,Rha 8.2%,Xyl 3.7%,GlcA 5.3%,Man 1.8%,Fuc 2.5%.3.Preliminary study on hypoglycemic activity of FCPS.The inhibitory effect of FCPS onα-amylase and α-glucosidase in vitro was studied.The results showed that the inhibitory effect of FCPS on these two enzymes was dose-dependent.When the concentration of FCPS reached 5 mg/mL,the inhibition rates of the two enzymes were 52.61%and 46.48%,respectively.The hypoglycemic effect of FCPS on diabetic type II mice was studied.The results showed that FCPS could effectively control the weight loss of mice,and the average body weight of mice in the high dose group(240 mg/kg)was similar to that of the positive drug control group.The average fasting blood glucose concentration of the three dose groups of FCPS decreased by 29.1%、18.6%and 14.1%,respectively.Compared with the model group,the glucose tolerance level of positive drug control group and high dose FCPS group decreased significantly,while the glucose tolerance level of middle dose FCPS group decreased slightly.Therefore,FCPS can improve the effect of the glucose tolerance level in diabetic mice.The preliminary study on the hypoglycemic experiment of FCPS in vivo has showed that FCPS could reduce fasting blood glucose and glucose tolerance in diabetic type II mice and improve the weight loss of mice.As the results,it can provide a theoretical idea to develop and utilize leaves resources from fig tree. |
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