| Dendrobium officinale is the best of dendrobiums.In this study,the flash extraction,technology was optimized by response surface methodology,and polysaccharides were extracted from Dendrobium officinale,with 4 different extraction methods,including flash extraction,ultrasonic-assisted extraction,homogenate-assisted extraction and conventional thermal extraction.After separation and purification,Dendrobium polysaccharides containing a homogeneous constituent were obtained with the 4 different extraction methods.The effects of flash extraction,on the property,feature and functional activity of Dendrobium officinale polysaccharides was researched through a series of physical and chemical tests and feature analyses,antioxidant activity indices determination and comparison,and hypoglycemic activity comparison.The main results are as follows:(1)In the study,soaking duration,flash extraction,duration and flash extraction,speed were selected to optimize the extraction technology by response surface methodology.The response surface test and fitting optimization showed the optimum technological condition:soaking duration is 19h;flash extraction,duration is 184s;flash extraction,speed is 4600r/min.Under this condition,the extraction ratio of Dendrobium officinale polysaccharides is 30.77%±0.04,the relative error to the model-based predictive value being 0.13%.Dendrobium officinale polysaccharides were extracted with 4 different methods,including flash extraction,,ultrasonic-assisted extraction,conventional thermal extraction and homogenate-assisted extraction,under the optimized condition.(2)Using DEAE-52 cellulose chromatogram,4 different constituents were separated from the Dendrobium officinale polysaccharides extracted with 4 different extraction methods,with proteins removed by papain,colors removed by active carbon method and small molecular weight impurities removed by dialysis.Then,the most abundant elution fractions were numbered,collected and concentrated.Finally,the elution fractions were purified using a Sephadex G-100 column.There was a single symmetrical peak in the elution curve,suggesting that the Dendrobium officinale polysaccharides extracted above had a single constituent,and its relative molecular weight was uniformly and intensively distributed.These elution peaks were numbered,collected,concentrated,dialyzed and freeze-dried respectively,obtaining pure homogeneous polysaccharide compositions DOP-A(flash extraction,),DOP-B(ultrasonic-assisted extraction),DOP-C(conventional thermal extraction)and DOP-D(homogenate-assisted extraction).(3)Then,the physical and chemical properties of pure polysaccharides DOP-A,DOP-B,DOP-C and DOP-D,extracted from Dendrobium officinale with 4 different methods,were tested,and a pilot study was conducted on their features.According to Molisch’s reaction,there were carbohydrates in the 4 kinds of Dendrobium officinale polysaccharides;Fehling’s solution test showed that there was no solu’ole reducing sugar in the 4 kinds of Dendrobium officinale polysaccharids;iodide-potassium iodide solution test showed that there was no starch in the 4 kinds of Dendrobium officinale polysaccharides;biuret reagent and ninhydrin solution test showed that there was no protein in the 4 kinds of Dendrobium officinale polysaccharides.Freezing-thawing test showed that centrifugation didn’t occur.The infrared spectroscopic analysis results of the 4 Dendrobium officinale polysaccharides were compared.The results show that the Dendrobium officinale polysaccharides extracted with 4 different methods have a similar infrared scanning waveform trend and characteristic absorption peak,but there is an obvious difference in the transmission factor and stretching vibration of some functional groups.(4)A preliminary comparison was made of the in vitro antioxidant activities and hypoglycemic activities of the Dendrobium officinale polysaccharides extracted with 4 different methods.As can be seen from the comparison of the 7 antioxidant indices of the 4 Dendrobium officinale polysaccharides,:flash extraction,could improve the antioxidant activity of Dendrobium officinale polysaccharides,while it was still unknown whether flash extraction,had an obvious inhibitory action on one of the antioxidant indices of polysaccharides.As can be seen from the comparison of 2 hypoglycemic indices of the 4 Dendrobium officinale polysaccharides,flash extraction,could improve the hypoglycemic activity of Dendrobium officinale polysaccharides,while it was still unknown whether flash extraction,had an obvious inhibitory action on one of the hypoglycemic indices of polysaccharides. |
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