| Jerusalem artichoke is a kind of perennial herbage,which has low requirements on the growing environment,high yield,strong disease resistance,and various ways of comprehensive energy utilization.It is one of the most promising energy crops in China.Jerusalem artichoke polysaccharide extracted from the tuber of Jerusalem artichoke is a kind of dietary fiber.It has various biological activities such as anti-tumor,anti-oxidation and intestinal microbial regulation.It is of great significance in livestock breeding and food processing.Current reports on the functional results of polysaccharides vary,and there are many factors causing functional differences.However,there are no studies on functional differences and structural differences between early and late maturity Jerusalem artichoke varieties.To solve the above problems,four Jerusalem artichoke varieties were used as raw materials in this experiment,among which early maturing Jerusalem artichoke were JA-1 and JA-2,and late maturing Jerusalem artichoke were JA-3 and JA-4.Through field planting experiments,field indexes such as phenology and yield were measured.After harvest at maturity stage,the early and late Jerusalem artichoke polysaccharides were selected and extracted,which were denoted as JAP-2 and JAP-4.The purified polysaccharides were selected and their content was determined by phenol-sulfuric acid method and DNS method.The antioxidant activity was determined by ultraviolet spectrophotometer in vitro.The monosaccharides were determined by Ion chromatography(IC).The molar mass and polydispersity coefficient of polysaccharide were determined by Gel permeation chromatography-refraction-multi-angle laser scattering(GPC-RI-MALS).Fourier Transform Infrared Spectrometry(FT-IR)was used to determine the glycosidic bond of Jerusalem artichoke polysaccharide.The spatial structure and repetition units of polysaccharides were finally determined by one-dimensional and two-dimensional Nuclear Magnetic Resonance(NMR)resonance spectra.Three parallel units were measured in each group.The research results are as follows:1.The vegetative growth period of early Jerusalem artichoke is 42 days shorter than that of late artichoke,and the reproductive growth period of early Jerusalem artichoke was 10 days longer than that of late artichoke.The plant height of early maturing Jerusalem artichoke was significantly higher than that of late maturing Jerusalem artichoke during the whole growth period(P<0.001),and the stem diameter of late maturing Jerusalem artichoke in June,July and August was significantly higher than that of early maturing Jerusalem artichoke(P<0.05).The yield of two early maturing cultivars were significantly lower than that of two late maturing cultivars(P<0.05).The CP content of late maturing Jerusalem artichoke tuber were significantly higher than that of early maturing Jerusalem artichoke tuber(P<0.05),the DM content of early maturing artichoke straw were significantly higher than that of late maturing artichoke straw(P<0.001),the JA-2 dry matter content of early Jerusalem artichoke residue after polysaccharide extraction were the highest(94.57%),which was significantly higher than that of the other three cultivars(P<0.001).2.The polysaccharide content of JAP-2 and JAP-4 were 75.49%and 79.70%,the polysaccharide content of JAP-4 was significantly higher than that of JAP-2(P<0.01),the total sugar content of JAP-4 was significantly higher than that of JAP-2(P<0.01),and the extraction value of late maturity Jerusalem artichoke was higher than that of early maturity Jerusalem artichoke.The oil holding capacity of JAP-2 and JAP-4 respectively were 1.71±0.32g/g and 3.56±0.25 g/g,and the oil holding capacity of JAP-4 was significantly higher than that of JAP-2(P<0.05).The free radical scavenging rate of JAP-2 was always higher than that of JAP-4,and gradually increased within a certain concentration range.Finally,the scavenging rate was basically the same,and VC was taken as the positive control,which basically reached more than 80%.3.Results showed that the JAP-2 and JAP-4 have different monosaccharides.JAP-2 was composed of Fru,Gal and Glc,with a molar ratio of 75.10:0.31:24.59.Of these,Fuc was the predominant components with a proportion of 75.10%.The JAP-2 was found to consist of four types of the monomer residues,and the main interchain glycosidic linkages were t-Fru(f),t-Glc(p),1-Fru(f)and 1-Fru(f),and the molecular mass was 0.97×10~3 g/mol.Regarding the molecular conformation,JAP-2 was a short-chain small molecule,and having a rough surface of fragments or clumps in the terms of morphology.JAP-4 was composed of Ara,Fru and Glc,with a molar ratio of 0.08:84.25:13.67.Of these,Fuc was the predominant components with a proportion of 84.25%.The JAP-4 was found to consist of six types of the monomer residues,and the main interchain glycosidic linkages were t-Fru(f)、t-Glc(p)、1-Fru(f)、1-Fru(f)、1,6-Fru(f)and 1,6-Fru(f),and the molecular mass was 2.08×10~3 g/mol.Regarding the molecular conformation,JAP-4 was a long-chain macromolecule,and having a rough surface of Cauliflower in the terms of morphology.In conclusion,oligosaccharides were the main polysaccharides extracted from early maturing Jerusalem artichoke,while long chain polysaccharides were extracted from late maturing Jerusalem artichoke.This study found that there were significant differences in the polysaccharides in the tubers of Jerusalem artichoke at different varieties,which provided a scientific basis for targeted screening of polysaccharides with specific functions.At the same time,it also provided theoretical support for a comprehensive study on the biological function of Jerusalem artichoke polysaccharides and the development of functional products. |
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