Abstract:
This study was designed to investigate the effect of quercetin, its glycosylated conjugate rutin and various combination of the two flavonoids on carbohydrate hydrolyzing enzymes associated with type-2 diabetes (α-amylase and α-glucosidase) in a bid to understand the possible mechanisms by which quercetin and rutin ameliorate degenerative conditions. The effect of the flavonoids on α-amylase and α-glucosidase activities and pro-oxidant induced lipid peroxidation in rats pancreas homogenates were investigated, as well as the antioxidant activities as the radicals [1,1-diphenyl-2-picrylhydraxyl (DPPH), nitric oxide (NO), hydroxyl (OH)] scavenging and Fe2+-chelating abilities. Rutin had a significantly higher DPPH* (EC50 = 0.264μM), ABTS* (7.1μmol.TEAC/100g), OH* (EC50 = 0.065μM) and NO* (EC50 = 0.101μM) scavenging abilities than quercetin [DPPH (EC50 = 0.349μM), ABTS (4.7μmol.TEAC/100g), OH* radicals (EC50 = 0.098μM), NO* (EC50 = 0.119μM)]. Similarly, rutin (EC50 = 0.048μΜ) also exhibited a significantly (P<0.05) higher inhibition of Fe2+ - induced lipid peroxidation than qucercetin (EC50 = 0.075μΜ). Furthermore, rutin had a stronger inhibition of α-amylase (IC50 = 0.043μM) and α-glucosidase (IC50 = 0.037μM) activities than quercetin [α-amylase (IC50 = 0.061μM); α-glucosidase (IC50 0.038μM)]. A combination of Quercetin and Rutin (1:3) showed the strongest inhibition (P<0.05) of α-amylase activity (IC50 = 313.87μg/L) while Quercetin showed the least inhibition of α-amylase (IC50 507.61μg/L) activity. Quercetin also had the least inhibition of α-glucosidase activity (IC50 346.78μg/L), while a combination of Quercetin and Rutin (1:3) showed the highest inhibitory ability (IC50 254.45μg/L). This study revealed that rutin had a higher inhibitory ability on key enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) than quercetin. Furthermore, a combination of quercetin and rutin (1:3) had highest inhibitory abilities against the enzymes.
