Antioxidant compounds of Kielmeyera coriacea Mart. with α-amylase, lipase and advanced glycation end-product inhibitory activities

Abstract

Chronic hyperglycemia and hyperlipidemia are associated with excessive formation of reactive oxygen species and advanced glycation end-products. The present study aimed to evaluate the potential in vitro antidiabetic properties of Kielmeyera coriacea inner bark. The main phytochemical compounds were identified by UHPLC-ESI/MSⁿ and the ethanol extract and its fractions were used to evaluate their antioxidant and anti-glycation capacities, as well as their inhibitory potential against glycoside and lipid hydrolases activities. The polar fractions, especially the n-butanol fraction, had free radical scavenging and quenching properties (ORAC and FRAP values>1800 and 1000 µmol trolox eq/g, respectively, and DPPH IC₅₀<4 µg/mL), and inhibited ROS production (p < 0.01), lipid peroxidation (p < 0.001), glycation (IC₅₀ ~ 10 µg/mL in the BSA-fructose assay; IC₅₀ ~ 200 µg/mL in the BSA-methylglyoxal and arginine-methylglyoxal assays), α-amylase (IC₅₀<0.1 µg/mL) and lipase (IC₅₀<5 µg/mL), with no cytotoxicity. Biomolecules well-known as potent antioxidants were identified for the first time in the inner bark of K. coriacea, such as protocatechuic acid, epicatechin and procyanidins A, B and C. Together, our results support the antioxidant, anti-glycation and glycoside and lipid hydrolases inhibitory properties of the inner bark of K. coriacea, a species found in the Brazilian savanna, which makes it especially useful to combat oxidative stress and hyperglycemia and hyperlipidemia.

Keywords: Antioxidants; Diabetes; Enzyme inhibition; Glycation; Polyphenols.