| Bletilla striata(Bletilla striata(Thunb.)Reichb.f.)is a perennial herb of the genus Bletilla in the family Orchidaceae,rich in polysaccharides,militarine,terpenoids,and various biologically active components of the class Lianfi.Among them,Bletilla striata polysaccharide(BSP)is the main bioactive substance in Bletilla striata,which has anti-inflammatory and antibacterial effects,astringent and hemostatic effects,swelling and muscle growth,etc.It has great development prospect and research value.Bletilla striata polysaccharide(BSP)is one of the main bioactive substances,which has the effects of anti-inflammatory and antibacterial,astringent and hemostatic,swelling and muscle growth,etc.It has great development prospects and research value.At present,the research on Bletilla striata polysaccharide is mainly focused on the activity of hot water extracted polysaccharide,while the enzymatic digestion of Bletilla striata polysaccharide and its activity are less studied.In this paper,we firstly summarized the research progress of plant polysaccharides,optimized the enzymatic extraction and process conditions of Bletilla striata polysaccharides,carried out preliminary structural characterization of the purified components of the crude polysaccharide extract of Bletilla striata,and evaluated the biological activity and application studies of Bletilla striata polysaccharides,aiming to provide a theoretical basis for the functional research and product diversification development of Bletilla striata polysaccharides.The main contents and conclusions of the study are as follows:(1)Optimization of the process of extracting polysaccharide from Bletilla striata by complex enzymatic method.The basic components of raw material of Bletilla were determined,the moisture content of Bletilla was 8.30±0.05 g/100g,ash content was0.34±0.02 g/100g,crude protein content was 4.05±0.56 g/100g,crude fiber content was 10.29±0.04 g/100g and polysaccharide content was 54.26±0.36 g/100g.Based on the single-factor test,the optimal process conditions for the extraction of Bletilla striata polysaccharides by complex enzymes were optimized by Box-Behnken Design:cellulase 2%and papain 1.5%,enzymatic digestion time 58 min,enzymatic digestion temperature 51°C,enzymatic digestion p H 5.2,the yield of Bletilla striata polysaccharides was 24.57±0.56%,compared with the hot water extraction(15.55±0.01%),the polysaccharide yield increased by 58.07%.The hot water extract(BSP-W)and complex enzyme extract(BSP-E)of Bletilla striata polysaccharides contained 0.23±0.05%and 0.12±0.04%of glyoxylate,4.09±0.06%and 5.36±0.07%of reducing sugars,64.17±0.05%and 59.36±0.05%of total soluble sugars,0.10±0.43%and 0.05±0.34%of protein content,respectively.The SEM results showed that the surface of BSP-E showed a loose and porous mesh structure,while BSP-W showed an uneven lamellar structure.(2)Purification and structural characterization of crude polysaccharides of Bletilla striata.The Sevag method was used to remove the protein from BSP-E,and the effect was better when the number of treatments reached 4 times,when the removal rate of protein reached 79.76%and the loss rate of polysaccharide was12.33%.The purified fraction of Bletilla striata polysaccharide(BSP)was obtained by Sephacryl S-400 HR purification,the soluble total sugar content in BSP was92.75±0.32%and the reducing sugar content was:1.32±0.01%,no glyoxylate was detected in BSP,and there was no absorption peak at 260～280,which indicated that the purified fraction did not contain nucleic acid and protein,which indicated that the crude polysaccharide of Bletilla striata The purification effect was obvious.The heavy average molecular weight(Mw)of BSP was 2.12×10~4 Da,the number average molecular weight(Mn)was 1.54×10~4 Da,the dispersion coefficient was 1.38±0.32,and the weight average radius(Rw)was 66.4,which indicated that the molecular conformation of BSP in solution was a highly branched polymer.BSP was mainly composed of six monosaccharides,rhamnose,arabinose,fucose,galactose,glucose and mannose,with molar percentages of 0.26%,0.31%,0.32%,1.13%,22.42%and75.56%,respectively,indicating that BSP is a heteropolysaccharide with mannose and glucose as the main components.Fourier transform infrared spectroscopy(FT-IR)analysis showed the characteristic absorption peaks of sugar functional groups(-OH,O-H,C-O-C)in the BSP fraction,indicating that BSP may contain pyranose rings,and the results of Congo red test showed the presence of triple helix conformation in BSP.(3)In vitro antioxidant capacity and cosmetic efficacy study of BSP polysaccharides.The results of in vitro antioxidant test showed that BSP,BSP-E and BSP-W all had strong antioxidant ability and showed concentration-dependent relationship,and the inhibition rate of BSP on DPPH,hydroxyl radical,iron reduction and lipid peroxidation was significantly stronger than that of BSP-E and BSP-W.This indicated that the purification significantly increased the scavenging ability of BSP-E and BSP-W for free radicals and had good ferric reducing ability.In addition,the scavenging ability of free radicals from BSP-E was stronger than that of BSP-W,which indicated that the enzymatic extraction of polysaccharide was better than the hot water extraction of polysaccharide in terms of antioxidant activity;the strong absorption of Bletilla striata polysaccharide solution between 260 and 320 nm indicated that Bletilla striata polysaccharide had good anti-short-wave ultraviolet(UVB)activity and could be used as a potential material for natural sunscreen;Bletilla striata polysaccharide had a certain degree of antioxidant activity in both low relative humidity and high relative humidity environments.It has a certain degree of hygroscopicity in both low and high relative humidity environments,and has a moisturizing property not weaker than glycerol.The results of this study provide ideas for efficient extraction and purification methods of Bletilla polysaccharides,research on the relationship between molecular weight,monosaccharide composition and structure and biological activity,provide a theoretical basis for the development of functional products of Bletilla,and lay the foundation for the exploitation of Bletilla resources and their industrial production. |
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