Abstract
The antihyperglicemic activity of crude extract from Moringa oleifera leaves and isolation of phenolic compounds with antioxidant activity using bioguided assay were employed by the first time in leaves cultivated in Brazil. The hydroalcoholic extract (HE) was produced by using ethanol:water (80:20 v/v) and purified by solid-liquid procedure using solvents in ascending order of polarity. The ethyl acetate fraction (Fr-EtOAc) presented high antioxidant potential and it was purified using chromatographic techniques rendering isolated compounds that were identified from the spectral data. The HE extract (500 mg kg-1) was adimistrated in diabetic rats induced by streptozotocin and chemical markers and lipid peroxidation in liver and kidney were evaluated. The Fr-EtOAc showed high antioxidant potential by FRAP reduction method (1678 µmol Fe2+ g-1), DPPH and ABTS scavenging methods (526.7 and 671.5 µmol TEAC g-1 respectively) and ORAC assay (3560.6 µmol TEAC g-1). Therefore, the Fr-EtOAc was purified and yielded three bioactive subfractions (S-12, S-13 abd S-15) that were rechromatoghaphed in HPLC-SemiPrep. After that, two main bioactive glycosylated flavonoids (isoquercitrin and astragalin) and phenolic acid (3-O-caffeoylquinic acid) were obtained. Additionally, the HE extract provided protection against oxidative damage in liver and kidney of diabetic rats ameliorating endogenous antioxidant defenses by increase catalase (CAT), glutathione S-transferase (GST) and non-protein thiol groups (NPSH) levels as well as decreased the lipid peroxidation in these tissues. Our results indicate that three phenolic compounds with high antioxidant activity were isolated and, the chemical composition of HE crude extract, rich in flavonoids glycosylated could be intimately related to antihyperglycemic action. So, it is possible to suggest that these compounds may be used as chemical biomarkers for this plant in Brazil, ensuring quality and supporting the use of aerial parts in tradicional medicine.
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