CHEMICAL, FUNCTIONAL, ANTIOXIDANTS, ANGIOTENSIN-1-CONVERTING ENZYMES AND ALPHA AMYLASE-GLUCOSIDASE INHIBITORY PROPERTIES OF WHITE MELON SEED (Cucumeropsis mannii) PROTEINS

Abstract

Plant seeds are essential source of foods and medicine for humans. It contains vital nutrients and pytochemicals which promote normal body growth and health. The white melon seed (Cucumeropsis mannii) contains essential nutrients and medicinal potential. Despite these potentials, the white melon seeds (Yoruba = itoo) are underutilized; hence, this study was aimed at determining chemical, functional, antioxidants, angiotensin-1-converting enzymes and alpha amylase-glucosidase inhibitory properties of the seed flour. The white melon seed was purchased at Oja Oba Akure, Nigeria. The seed were processed as raw (UDF) defatted (DMF), isolate (MPI) and hydrolysate (MPH). The flour samples were evaluated for proximate composition, minerals, amino acids, anti-oxidant activities, alpha amylase-alpha glucosidase and angiotensin converting enzymes inhibition potentials. The result of the proximate analysis ranged as follows: moisture (4.74±0.21 - 1.39±0.05 g/100 g), crude fibre (3.77±0.05 -0.31±0.02 g/100 g), crude fat (17.05±0.23 – 6.71.6±0.21 g/100 g), Ash content (4.85±0.03- 1.91±0.01 g/100 g) protein (85.61±0.61 -38.24±0.12 g/100 g), carbohydrate (33.34±0.26 – 3.52±0.11 g/100 g) and energy (441.80±4.15-417.10±1.03 Kcal/100 g). The melon seed flour contains appreciable amount of minerals with potassium having the highest (4.53±0.04 – 1.55±0.07 mg/100 g) concentration. The essential amino acid of white melon seed flour ranged between 3.42 g/100 g of protein and 6.76 g/100 g of protein, while glutamic acid was found to be in highest concentration of amino acids, and cysteine was the least. The antioxidant activities of the flours ranged as follows: ferric reducing antioxidant powder (1.04-29.95%), DPPH (19.65- 80.89%), Fe-chelating (27.79 -91.79%), and were dose dependent. The inhibitory potential (%) of melon seed flour samples on apha-amylase-glucosidase enzymes were dose dependent, and the values ranged as follows: 10.47±0.45-93.82±0.40 and 4.37±0.38-91.82±0.04. The angiotensin converting enzymes inhibitory potential of the flours ranged from 65.43±0.23 - 90.03±0.18%, and were higher than Captopril (76.40±0.26%). Hence, the melon seed protein hydrolysate may be suitable as antidiabetic and antihypertensive agents, and also, could be incorporated into food formulations like functional and complimentary foods.