Synthesis,antioxidant and anti-hypoxia activities of 6-hydroxygenistein and its methylated derivatives
Objective:Hypoxia is a common pathological phenomenon,usually caused by insufficient oxygen supply or inability to use oxygen effectively.Hydroxylated and methoxylated flavonoids have significant anti-hypoxia activity.This study aims to explore the synthesis,antioxidant and anti-hypoxia activities of 6-hydroxygenistein(6-OHG)and its methoxylated derivatives.Methods:The 6-OHG and its methoxylated derivatives,including 4',6,7-trimethoxy-5-hydroxyisoflavone(compound 3),4',5,6,7-tetramethoxyisoflavone(compound 4),4',6-imethoxy-5,7-dihydroxyisoflavone(compound 6),and 4'-methoxy-5,6,7-trihydroxyisoflavone(compound 7),were synthesized by methylation,bromination,methoxylation,and demethylation using biochanin A as raw material.The structure of these products were characterized by 1hydrogen-nuclear magnetic resonance spectroscopy(1H-NMR)and mass spectrometry(MS).The purity of these compounds was detected by high pressure chromatography(HPLC).The antioxidant activity in vitro was investigated by 1,1-diphenyl-2-picrylhydrazyl radical(DPPH)free radical scavenging assay.PC12 cells were divided into a normal group,a hypoxia model group,rutin(1×10-9-1×10-5 mol/L)groups,and target compounds(1×10-9-1×10-5 mol/L)groups under normal and hypoxic conditions.Cell viability was detected by cell counting kit-8(CCK-8)assay,the target compounds with excellent anti-hypoxia activity and the drug concentration at the maximum anti-hypoxia activity were screened.PC12 cells were treated with the optimal concentration of the target compound or rutin with excellent anti-hypoxia activity,and the cell morphology was observed under light microscope.The apoptotic rate was determined by flow cytometry,and the expressions of hypoxia inducible factor-1α(HIF-1α)and vascular endothelial growth factor(VEGF)were detected by Western blotting.Results:The structure of 6-OHG and its 4 methylated derivatives were correct,and the purity was all more than 97%.When the concentration was 4 mmol/L,the DPPH free radical removal rates of chemical compounds 7 and 6-OHG were 81.16%and 86.94%,respectively,which were higher than those of rutin,the positive control.The removal rates of chemical compounds 3,4,and 6 were all lower than 20%.Compared with the normal group,the cell viability of the hypoxia model group was significantly decreased(P<0.01).Compared with the hypoxia model group,compounds 3,4,and 6 had no significant effect on cell viability under hypoxic conditions.At all experimental concentrations,the cell viability of the 6-OHG group was significantly higher than that of the hypoxia model group(all P<0.05).The cell viability of compound 7 group at 1×10-7 and 1×10-6 mol/L was significantly higher than that of the hypoxia model group(both P<0.05).The anti-hypoxia activity of 6-OHG and compound 7 was excellent,and the optimal drug concentration was 1×10-6 and 1×10-7 mol/L.After PC12 cells was treated with 6-OHG(1×10-6 mol/L)and compound 7(1×10-7 mol/L),the cell damage was reduced,the apoptotic rate was significantly decreased(P<0.01),and the protein expression levels of HIF-1α and VEGF were significantly decreased in comparison with the hypoxia model group(both P<0.01).Conclusion:The optimized synthesis route can increase the yield of 6-OHG and obtain 4 derivatives by methylation and selective demethylation.6-OHG and compound 7 have excellent antioxidant and anti-hypoxia activities,which are related to the structure of the A-ring ortho-triphenol hydroxyl group in the molecule.
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