The Extraction, Structural Analysis And Biological Activity Of Water-soluble Polysaccharides From Banana Flowers

Bananas are widely cultivated and therefore the resource of banana flower polysaccharides is abundant.However,studies on the extraction,structural identification,chemical components and biological activities of banana flower polysaccharides are relatively few.Therefore,the stamens and bracts of bananas obtained from the extracted and dehybridized stamens and bracts of banana species commonly found in Guangdong and Guangxi regions were used as the objects of this paper.To study the structural characteristics,chemical composition,antioxidant activity and hypoglycemic activity of polysaccharide fractions of banana stamens and bracts from different species,and to provide theoretical basis for the future development of functional products of banana flower polysaccharides.The results of the study are as follows:(1)Analysis of the extraction and chemical fraction of polysaccharides from stamens and bracts of bananasThe banana stamens and bracts of Musa × paradisiaca L.1,Musa ×paradisiaca L.2,Musa basjoo S,Musa balbisiana and Musa nana Lour were extracted by Ethanol subsiding method,deproteinized by sevag method and de-hybridized by dialysis to obtain banana flower crude polysaccharides,which were banana stamens polysaccharides Bsp1,Bsp2,Bsp3,Bsp4,Bsp5 and banana flower bracts polysaccharides Bbp1,Bbp2,Bbp3,Bbp4,Bbp5 in this order.The highest extraction rate of banana stamen polysaccharide Bsp4 reached 32.57 ± 0.65 %,and the highest extraction rate of banana bract polysaccharide Bbp1 reached 19.82 ±0.04 %.The total sugar content,glyoxylate content and protein content of polysaccharides were determined.Among the banana stamens polysaccharides,Bsp2 had the highest total sugar content,reaching 68.94± 1.32 %.Among the banana bracts polysaccharides,Bbp1 had the highest total sugar content,reaching 45.13 ± 1.24 %.The glyoxylate content of banana flower polysaccharides were all high,with the glyoxylate content of banana stamen polysaccharide Bsp5 reaching 52.62± 2.17 % and the glyoxylate content of banana bract polysaccharide Bbp1 reaching 59.20 ± 2.90 %.The protein content of all banana flower polysaccharides after purification operation was low,and the lowest content of Bsp1 was found in banana stamens polysaccharides with a protein residue of 0.30 ± 0.07 %;the lowest content of Bbp2 was found in banana bracts polysaccharides with a protein residue of 0.02 ± 0.12 %.(2)Structural analysis of stamens and bracts polysaccharides in bananasThe banana stamens and bracts polysaccharides were examined by high performance liquid chromatography(HPLC),infrared spectroscopy(FT-IR),thermogravimetric analysis(TG-DSC),scanning electron microscopy(SEM),and Congo red experiment.The results showed that both banana stamens and bracts polysaccharides are acidic polysaccharides containing pyran ring,and mainly consist of monosaccharides such as D-galacturonic acid,D-galactose and L-arabinose,and banana stamens and bracts polysaccharides have good thermal stability within 200 ℃,and the surface morphology has pores,loose,flattened fragment accumulation,and both are polysaccharides with triple helix structure.(3)Investigation on the biological activity of banana flower polysaccharidesThe antioxidant activity of banana stamens and bracts polysaccharides was evaluated in vitro,and the antioxidant activity of both banana stamens polysaccharides was higher than that of bracts polysaccharides through the experiments on the scavenging ability of free radicals and total antioxidant capacity,and the antioxidant capacity was positively correlated with the concentration of polysaccharides.The highest DPPH radical scavenging activity of Bsp2 was observed at 2.5mg/m L,reaching 65.31±0.54 %.The highest hydroxyl radical scavenging activity of Bsp4 was observed at 1.0 mg/m L,reaching 94.23 ± 0.12 %.In regard to superoxide anion scavenging ability,stamens polysaccharide was superior to bracts polysaccharide.At 1.0 mg/m L,the highest superoxide anion radical scavenging activity of Bsp2 was achieved at23.06 ± 0.91 %.The highest total antioxidant capacity of Bsp4 was achieved at 2.5 mg/m L with 29.27 ± 0.71 %.Selecting Bsp2,a stamen polysaccharide with high overall antioxidant capacity,for cellular antioxidant experiments,the experimental results showed that Bsp2 could inhibit intracellular ROS production,increase the activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GSH-Px)and reduce the content of malondialdehyde(MDA)in HepG2 cells induced by ABAP damage.In hypoglycemia,banana stamens and bracts polysaccharides showed stronger inhibition of α-glucosidase.Compared with the positive control acarbose,banana stamens and bracts polysaccharides inhibited α-glucosidase activity to a higher extent.Combining antioxidant and α-glucosidase activity inhibition experiments,Bsp2 was selected for glucose metabolism experiments at the cellular level,and the experimental results showed that Bsp2 polysaccharide could increase the glucose consumption of IR-HepG2 cells and could effectively improve the level of glucose metabolism.