Phenolic constituents and modulatory effects of Raffia palm leaf ( Raphia hookeri ) extract on carbohydrate hydrolyzing enzymes linked to type-2 diabetes

Abstract This study sought to investigate the effects of Raffia palm ( Raphia hookeri ) leaf extract on enzymes linked to type-2 diabetes mellitus (T2DM) and pro-oxidant induced oxidative stress in rat pancreas. The extract was prepared and its α-amylase and α-glucosidase inhibitory effects were determined. Radical [2,2-diphenyl-1-picrylhydrazyl (DPPH)] scavenging and Fe 2+ -chelating abilities, and inhibition of Fe 2+ -induced lipid peroxidation in rat pancreas homogenate were assessed. Furthermore, total phenol and flavonoid contents, reducing property, and high performance liquid chromatography diode array detector (HPLC-DAD) fingerprint of the extract were also determined. Our results revealed that the extract inhibited α-amylase (IC 50  = 110.4 μg/mL) and α-glucosidase (IC 50  = 99.96 μg/mL) activities in concentration dependent manners which were lower to the effect of acarbose (amylase: IC 50  = 18.30 μg/mL; glucosidase: IC 50  = 20.31 μg/mL). The extract also scavenged DPPH radical, chelated Fe 2+ and inhibited Fe 2+ -induced lipid peroxidation in rat pancreas all in concentration dependent manners with IC 50 values of 402.9 μg/mL, 108.9 μg/mL and 367.0 μg/mL respectively. The total phenol and flavonoid contents were 39.73 mg GAE/g and 21.88 mg QAE/g respectively, while the reducing property was 25.62 mg AAE/g. The HPLC analysis revealed the presence of chlorogenic acid (4.17 mg/g) and rutin (5.11 mg/g) as the major phenolic compounds in the extract. Therefore, the ability of the extract to inhibit carbohydrate hydrolyzing enzymes and protect against pancreatic oxidative damage may be an important mechanisms supporting its antidiabetic properties and could make Raffia palm leaf useful in complementary/alternative therapy for management of T2DM. However, further studies such as in vivo should be carried out.