Study On Extraction, Purification, Structure Identification And Adhesive Ability Of Polysaccharides From The Discs Of Parthenocissus Tricuspidata

Parthenocissus tricuspidata is a tendril-climber liana, belonging to the family ofVitaceae. Following touch stimulation, the tendrils can firmly adhere to different supportingobjects by flattening against the support surface, becoming adhesive discs in the tip andsubsequently secreting a kind of adhesive compound. The unique adhesion ability of P.tricuspidata has attracted great attentions from scientists since Darwin’s time. Previousstudies mainly focus on microstructure observation, cytochemical studies, attachment strengthquantification and bionic fabrication. The adhesive compound secreted from adhesive discshas been considered to be a kind of polysaccharide. However, there are only few reports aboutthe further details of this adhesive compound. Therefore, the adhesion mechanism of P.tricuspidata has not been completely confirmed and the further studies on the polysaccharidessecreted from adhesive discs are desirable and necessary. Herein, the aim of our study is toextract, isolate, purify and characterize the polysaccharides from adhesive discs of P.tricuspidata. The main contents have been summarized as follows:1. Response surface methodology (RSM) and central composite design (CCD) wereemployed to investigate the effects of extraction conditions on the extraction yield of crudepolysaccharide from adhesive discs. The optimum conditions were extraction time of3h,temperature of90°C and ratio of water to raw material of12:1, respectively. Under theseconditions, the maximum yield is6.642%.2. The water-soluble polysaccharides (PT1, PT2, PT3, PT4and PT5) were obtained fromadhesive discs through pretreatment, extraction with hot water, precipitation by95%ethanol,deproteinization and purification on DEAE-cellulose column and Sephadex G-100column.The homogeneity of polysaccharide was determined by HPGPC and the weight-averagemolecular weights of five polysaccharides were24699、202455、10537、253992and10382Daaccording to the calibration curve, respectively.3. The composition of sugars was determined by acid hydrolysis and GC analysis. PT1was composed of rhamnose (14.3%), arabinose (21.7%), fructose (30.9%) and galactose(33.0%). PT2consisted of arabinose (19.6%), fructose (44.2%) and galactose (36.1%).Besides rhamnose (16.1%), arabinose (17.0%), fructose (24.0%) and galactose (30.3%), PT3 also contained xylose (12.5%). PT4and PT5were composed of arabinose (21.4%), mannose(23.7%), galactose (29.7%) and glucose (25.2%) with the molar ratios of28.0:23.0:32.0:17.0and21.4:23.7:29.7:25.2，respectively.4. The chemical compositions and structures of polysacchrides were identified by aseries of chemical and instrumental methods, e.g. acid hydrolysis, periodate oxidation, Smithdegradation, methylation, IR and NMR spectra. According to the analysis of structureelucidation, they were major composed by (1�'3)-linked-Galp backbone with some branchingsites at O-6positions.5. The morphological structures of polysaccharides were investigated by atomic forcemicroscopy (AFM). PT1can easily form the aggregates with irregular shape under the higherconcentration. With the decrease of the concentration, PT1formed a kind of rope structure.PT2formed thin film-network-irregular rope structure along the decrease of concentration.The spherical particles with the diameter ranged from100to150nm were observed from theAFM image of PT3. As shown in the AFM image of PT-A, a long rope-like structure withsome branches is formed on the mica surface and the aggregates, caused by the entangledbranches, are also observed in some areas. The branched and linear rope-like structures areformed on mica surface by PT5.6. We also observed some branch-like structures and dendritic islands with irregularshapes at the edges of three samples, which were the typical fractal structure characterized byself-similarity. The classical Diffusion-Limited Aggregation (DLA) model was suggested todescribe the growth mechanism of the fractal structure. The fractal structure and dendriticislands produced by computer simulations closely approximate the structure obtained fromAFM observation.7. We also evaluate the adhesive property of polysaccharides and the results suggestedthat PT2was a potential bio-adhesive with the highest adhesion force value of295.8nN,compared to other bio-adhesive from animal or plant.