Preparation Of A Galangal Polysaccharide And Its Application In Emulsion Delivery System Loaded With Galangal Flavonoids

Galangal is a high-quality medicine food homology plant with abundant resources.It is widely used in the fields of medicine and condiments.It has the potential to be developed as functional foods.The current study on galangal mainly focuses on the pharmacological activities of flavonoids,diphenylheptanes and volatile oil.The bioactive compounds of galangal are not fully explored,and the functional properties are not clear,either.The extraction methods of its bioactive compounds are relatively simple,which limit the high-value utilization of galangal and also restrict the development of health food with bioactive ingredients in galangal as the core factor.In this study,galangal flavonoids and galangal polysaccharides were prepared by segmented extraction,and the potential of galangal polysaccharides as new emulsifiers to stabilize emulsions and control the rate of lipid digestion were investigated.The bioactive components in galangal were separated and reorganized to be a slow lipid digestion emulsion delivery system loaded with plant flavonoids and the aim of the research is to provide theoretical and methodological guidance for the extraction,processing and application of galangal bioactive components.The main results were listed as follows:(1)The galangal flavonoids were obtained by extracting galangal with 95%ethanol and then the residues were used to prepare polysaccharides.Enzymatic-assisted hot water extraction and enzymatic-assisted ultrasonic extraction were adopted under different p H conditions,followed by suction filtration,ultrafiltration,decompression concentration,ethanol precipitation,deproteinization,dialysis,static adsorption of macroporous resin,decompression concentration and freeze-drying,then six galangal polysaccharides were obtained.The total sugar contents of galangal polysaccharides range from 72.28%to 82.87%.The highest total sugar content belongs to the polysaccharide prepared by enzymatic-assisted ultrasonic extraction under alkaline condition(GP-UALK)while the lowest are polysaccharides prepared by enzymatic-assisted ultrasonic extraction under acidic condition(GP-UA)and enzymatic-assisted ultrasonic extraction under neutral condition(GP-UN).Galangal polysaccharides are all composed of seven monosaccharides:mannose,rhamnose,glucuronic acid,galacturonic acid,glucose,galactose and arabinose,among which galactose,arabinose and galacturonic acid are typical monosaccharides in galangal polysaccharides.The molecular weight of galangal polysaccharides does not exceed 1×10~5 Da,and they all share a highly branched structure,and GP-UN has the maximum molecular weight while the polysaccharide prepared by enzymatic-assisted hot water extraction under acidic condition(GP-HA)and GP-UALK have the minimum molecular weight.Galangal polysaccharides all have water and oil holding properties,and they can be stably dispersed in aqueous solutions.Galangal polysaccharide solutions are pseudoplastic fluids while they exhibit weak gel characteristics except for GP-HA.(2)The results of mulsifying activity index,emulsifying stability index and interfacial adsorption kinetics show that galangal polysaccharides have good emulsifying activity,emulsifying stability and interfacial activity.Among them,polysaccharide prepared by enzymatic-assisted hot water extraction under neutral condition(GP-HN)and GP-UN have the best emulsifying activity and emulsifying stability while GP-UN and GP-UALK have the best interfacial activity.Six galangal polysaccharides were used in the preparation of oil-in-water emulsions,and the emulsion properties,rheology and storage stability were measured.The results show that the average volume particle size distribution of emulsions stabilized by galangal polysaccharides are unimodal distribution,and the particle size is smaller than the two pectin-stabilized emulsions,and all emulsions are pseudoplastic fluids while they can maintain system stability through their own electrostatic repulsion.Emulsions stabilized by GP-HN,GP-UN and polysaccharide prepared by enzymatic-assisted hot water extraction under alkaline condition(GP-HALK)have the best storage stability,which is comparable to emulsions stabilized by tween-80,arabic gum,YM-115 and sodium caseinate.All galangal polysaccharides have good interfacial anti-bile salt replacement ability and delaying oil digestion ability confirmed by a in vitro simulation of gastrointestinal digestion model.Among them,GP-UALK and GP-UN have the best interfacial anti-bile salt replacement ability and delaying oil digestion ability,which are better than the five food-grade emulsifiers.GP-UN combines excellent emulsifying activity,emulsifying stability,interfacial activity,interfacial anti-bile salt replacement ability,and the ability to delay lipid digestion,and it can be used as a new emulsifier to stabilize slow-lipid-digestion emulsions.(3)The anti-solvent method was used to improve the purity of galangal flavonoids from the 95%ethanol extract of galangal.The flavonoids were analyzed by UPLC-Q-TOF-MS qualitatively and quantitatively.The results show that the content of total flavonoids in galangal flavonoids fraction is 53.98%,of which galangin,kaempferide,3-Methoxyl-galangin,pinocembrin and kaempferol accounts for 71.45%,15.43%,6.34%,6.11%,0.67%,respectively.Emulsions stabilized by GP-UN loaded with 0.01%(w/w)and 0.02%(w/w)galangin were prepared,and the properties,rheology and storage stability of the emulsion were evaluated.The results show that emulsions loaded with galangal flavonoids are pseudoplastic fluids with a small volume average particle size,and they are better than that of emulsions stabilized by gum arabic,YM-115 and tween-80.The retention rates of galangal flavonoids from high to low is:GP-UN emulsion,arabic gum emulsion,tween-80 emulsion,YM-115 emulsion.Based on the in vitro simulated gastrointestinal digestion model,the free fatty acid release rates from fast to slow is tween-80 emulsion,arabic gum emulsion,YM-115 emulsion and GP-UN emulsion,and the free fatty acid release rate from high to low is tween-80 emulsion,arabic gum emulsion,YM-115 emulsion,GP-UN emulsion.The bioaccessibilities of galangal flavonoids in emulsion delivery system range from 15.43%to 17.68%,and the bioaccessiblities of emulsion delivery system loaded with 0.01%(w/w)galangal flavonoids and 0.02%(w/w)galangal flavonoids are15.43%and 15.82%,respectively.Under the premise of effectively delaying lipid digestion,the slow lipid digestion emulsion stablized by galangal polysaccharide GP-UN can deliver galangal flavonoids stably and effectively.