Study On Extraction, Purification, Identification And Biological Activity Of The Flavonoids From Sugarcane Skin

With the byproduct of sugar cane industry--sugar cane skin as raw material,ultrasonic-assisted extraction of flavonoids were carried out with ethanol solution from sugarcane skin. The flavonoids were separated and purified by organic solvent, polyamide,Sephadex LH-20and RP-HPLC chromatography. Spectral data of MS,1H NMR,13C NMR,HSQC, HMBC and IR were used to identify their molecular structures. Then the bacteriostaticactivity, antioxidant activity and hypoglycemic activity of flavonoids were studied.Based on the yield and oxygen radical absorbance capacity (ORAC) value of flavonoids,after single-factor experiment and orthogonal test, the optimal conditions of extractingflavonoids from sugar cane skin were as follows: liquid-solid rate15:1(mL/g), extractiontime95min, extraction temperature60℃, ethanol concentration60%(v/v), extracted3times.Verification tests under optimal extraction conditions were conducted. The yield of flavonoidswas0.650±0.021%, and its ORAC value was933.8±16.7μmol TE/g, which were agreedclosely with the predicted onesFlavonoids from sugar cane skin were separated and purified by organic solvent,polyamide, Sephadex LH-20and RP-HPLC chromatography. The compound F was obtainedand identified as quercetin.The compound F had the inhibitory activities against sakazakii, Escherichia coli, Listeriamonocytogenes, and Staphylococcus aureus. The minimum inhibitory concentration (MIC) ofthe compound F against Staphylococcus aureus and Escherichia coli was2.5and5mg/mL,respectively, and the minimum bactericidal concentration (MBC) were5and10mg/mL,respectively. For Enterobacter sakazakii and Listeria monocytogenes, MIC and MBC wereabove10mg/mL.The antioxidant activities of flavonoids from sugar cane skin were studied by DPPHassay, ABTS assay and ORAC assay. The results showed that the ethyl acetate and30%ethanol elution fractions were antioxidant enriched parts. Their antioxidant activities werehigher than other parts, but lower than ascorbic acid (Vc). The antioxidant activity of thecompound F was higher than Vc. The DPPH and ABTS radical scavenging activity were188.6%and258.1%to Vc respectively when the concentration of the compound F was0.1mg/mL.The flavonoids from sugar cane skin showed inhibition to-glucosidase and the results showed stronger inhibition to maltose than to sucrase. The ethyl acetate and30%ethanolfractions were hypoglycemic enriched parts. Both of them showed higher hypoglycemicactivity than other parts, but lower than acarbose. The compound F had significantlyinhibitory effects on sucrase and maltase. The inhibition rate of sucrase was91.83%toacarbose when the concentration of the compound F was1.25mg/mL. The inhibition rate ofmaltase was90.46%to acarbose when the concentration of the compound F was5mg/mL.