Chemical composition, antioxidant activity and inhibitory capacity of alpha-amylase, alpha-glucosidase, lipase and non-enzymatic glycation, in vitro, of the leaves of Cassia bakeriana Craib

摘要

The prevalence of diabetes has increased rapidly in the world. Chronic hyperglycemia is associated with the complications of diabetes and is a major problem for medicine. The present study aimed to explore the antidiabetic potential of the leaves of Cassia bakeriana Craib (family Leguminosae) by evaluating the antioxidant activity and inhibition of alpha-amylase, alpha-glucosidase, lipase and glycation activities, in addition to determining the chemical constituents of the most active fractions. Therefore, the n-hexane extract (HE) and the ethanolic extract (EE) of the leaves were prepared by maceration, and the fractions were obtained by liquid-liquid extraction. The EE of C. bakeriana and its fractions showed high antioxidant activity in the oxygen radical absorbance capacity (ORAC) assay, being superior to the positive control (ascorbic acid). In the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the n-butanol fraction (BF) and ethyl acetate fraction (EAF) presented the best results. The EE showed higher inhibition of alpha-amylase activity (IC50 = 5.00 +/- 0.85 mu g mL(-1)) followed by EAF and BF. DF was the most active in the inhibition of alpha-glucosidase activity (IC50 = 359.55 +/- 2.90 mu g mL(-1)). The HE showed high inhibition of pancreatic lipase activity (IC50 = 25.27 +/- 8.78 mu g(-1)) and dichloromethane fraction (DF) and EAF were the most active inhibitors of glycation (IC50 = 37.85 +/- 0.49 and 53.25 +/- 11.24 mu g mL(-1), respectively). The fractionation of DF by semi-preparative HPLC-DAD led to the isolation of flavonoids: kaempferol-3-O-rhamnoside (I) and kaempferol (II), which were characterized by NMR and HPLC-ESI-MS. These compounds showed antioxidant activity in the ORAC method, but only compound 11 was active in the DPPH method. The isolated kaempferol (II) showed inhibitory activity against alpha-amylase (IC50 = 1.5 +/- 0.14 mu g mL(-1)). The compounds I and II showed inhibition of glycation (IC50 = 84.27 +/- 11.38 and 64.16 +/- 1.53 mu g mL(-1), respectively). Through the HPLC-ESI-MS analysis of the EE, DF and EAF, it was possible to propose the identification of some compounds such as acid phenolics, flavonoids, megastigmane, fatty acids and derivatives, sphingolipids, proanthocyanidins, cyanidin and anthraquinone.