HYPOGLYCEMIC AND HYPOLIPIDEMIC PROPERTIES OF UNRIPE PLANTAIN (Musa paradisiaca) PRODUCTS AND THEIR EFFECTS ON α-AMYLASE, α GLUCOSIDASE AND ANGIOTENSIN-I CONVERTING ENZYME

Abstract

Nutritional recommendations have recently been recognized as an important aspect of diabetes mellitus management. Therefore, this study investigates the antioxidants, antidiabetic and antihypercholesterolemic effects of unripe plantain products (flour, ‘amala’ and roasted) in lard/streptozotocin (STZ) - induced diabetic rats and high cholesterol fed animal models. The unripe plantain products were prepared and their free and bound phenolics extracted, subsequently, the total phenol, total flavonoid and antioxidant properties of the extracts were determined. The proximate analysis revealed the quantity of moisture, ash, protein, fat, crude fiber and the carbohydrate was determined by difference. In addition, the α-amylase, α-glucosidase and angiotensin-I converting enzyme (ACE) inhibitory abilities of the extracts were also determined. Thereafter, the in vivo antioxidant enzymes (GST and Catalase), antidiabetic (α-amylase and α-glucosidase inhibitory) and antihypercholesterolemic properties were assessed. The phenolic constituents and the melanoidins contents were characterized using gas chromatography (GC). The amylose, amylopectin, sugar and starch contents were also determined. The free soluble phenolics of all the unripe plantain products extracts exhibited higher total phenol (101.12 mg/100g), 103.02 mg/100g and 104.30 ma/100g for roasted, flour and ‘amala’ respectively) and total flavonoid contents(73.04 mg/100g, 77.24 mg/100g and 80.07 mg/100g for roasted, flour and ‘amala’ respectively) than their corresponding bound phenolics. The extracts exhibited strong antioxidant properties and inhibited α-amylase, α-glucosidase and ACE activities in vitro. Furthermore, the plantain diets significantly (p < 0.05) reduced the blood glucose level in the STZ induced diabetic rats by inhibiting α-amylase, α-glucosidase and ACE activities and also lowers cholesterol in high cholesterol fed rats. GC characterization revealed the presence of some phenolic acids and melanoidins quantities. The amylose content ranged from 25.05% (‘amala’) to 28.80 % (roasted) while amylopectin value ranged from 71.20% (roasted) to 74.95% (‘amala’). The starch content ranged from 73.19% (flour) to 76.08% (roasted). The sugar content ranged from 4.11% (roasted) to 6.92% (‘amala’). On the overall scale, roasted had the highest potential while flour had the least. This also indicates that processing improves unripe plantain products. Therefore, the observed high antioxidant capacity, antidiabetes and antihypercholesterolemic properties as well as all year round availability of unripe plantains can be exploited in the management of type-2 diabetes.