Near-infrared Spectroscopy Study On Polysaccharides And Monosaccharides Of Dendrobium Candidum

At present,most of the methods for the determination of polysaccharide content were the phenol sulfuric acid method and the anthrone sulfuric acid method in the colorimetric method,and the 3,5-dinitrosalicylic acid titration method.All of the above methods require sample pretreatment.And the measurement process is complicated and dangerous,the operation is cumbersome,the speed is slow,and the efficiency is low.Near-infrared spectroscopy technology has the advantages of high efficiency,speed and losslessness,and has been widely used in various fields in recent years.Near-infrared spectroscopy technology combined with chemometric methods to quickly determine the content of a certain component,and the establishment of rapid determination methods for multiple components have become modern research hotspots.In the research of this subject,the polysaccharide content of Dendrobium officinale was determined by the phenol sulfuric acid method,and the monosaccharide composition and the content of mannose,glucose,galactose and arabinose were determined by Pre-column derivatization.In order to improve the determination speed of polysaccharides and four monosaccharides,it was proposed to use near-infrared spectroscopy technology,combined with partial least squares method,to quickly and efficiently determine the content of Dendrobium officinale polysaccharides and typical monosaccharides.It provides the possibility to quickly determine the polysaccharide and monosaccharide content of large-scale Dendrobium officinale samples.The main results are as follows:(1)Response surface optimization of the ultrasonic-assisted hot water extraction of Dendrobium officinale polysaccharide extraction process,single-factor experiment results confirmed that the ultrasonic time has little effect on the extraction rate of polysaccharides.According to the response surface results,the optimal extraction process for polysaccharides from Dendrobium officinale was determined as the ratio of material to liquid 1:50,extraction temperature 85°C,and extraction time 120min.The model predictd that the extraction rate of polysaccharides under this condition is 40.30%,and it was verified that the extraction rate of polysaccharides was 40.33%.The ultrasonic-assisted polysaccharide extraction process significantly enhanced the extraction rate of polysaccharides.(2)The near-infrared spectra of the polysaccharide samples of Dendrobium candidum were collected,and the partial least square method was used to establish a rapid determination model of polysaccharide content.In this process,abnormal samples were collected one by one,and the pretreatment method was constantly changed.The best pretreatment method for the Dendrobium officinale polysaccharide model was determined to be the standard normalization(SNV)+first-order+N smoothing combination processing.Compared the modeling results of different modeling ranges.Finally,the root mean square error of the correction set(RMSEC)was 0.569,the correlation coefficient of the correction set(R_C~2)was 0.9596,the root mean square error of the verification set(RMSEP)was 0.868,and the correlation coefficient of the verification set(R_P~2)was 0.9385.The established rapid determination model of Dendrobium candidum polysaccharide content could realize the rapid determination of Dendrobium candidum polysaccharide content.(3)Used PMP to derive polysaccharide hydrolysate,determined the composition of monosaccharides and the content of Man,Glc,Gal and Ara.The quantitative models of mannose,glucose,galactose and arabinose were established.The RMSEC respectively was0.769,0.390,0.00291 and 0.00285,the RMSEP respectively was 0.812,0.277,0.00332,0.00440,and R_C~2 and R_P~2 were both greater than 0.9000.These models had good predictive performance,and the established models can be used to quickly determine the four monosaccharides of Dendrobium candidum.(4)In this study,the optimal extraction process for polysaccharides from Dendrobium officinale was determined,the polysaccharide content was extracted and determined to the greatest extent,and a quantitative analysis model for polysaccharides from Dendrobium officinale was established.The monosaccharide composition of Dendrobium candidum was explored and the quantitative analysis model of mannose,glucose,galactose and arabinose in Dendrobium candidum was established.The results showed that the combination of partial least squares method and near-infrared spectroscopy technology was feasible for rapid determination of multi-component content,and the established model could be used to efficiently and quickly determine the content of each component.