A major therapeutic approach presently used in managing Type 2 Diabetes mellitus is the use of ?-glucosidase and ?-amylase inhibitors. Hence the growing attention in the quest for medicinal plants of natural sources with inhibitory potentials on these enzymes. This study was done, therefore, to determine the inhibitory potentials of the different parts of three medicinal plants; Nigella sativum (seeds), Spondias mombin (leaves and stem bark), and Picralima nitida (seeds and mesocarp) on α-amylase and α- glucosidase as well as to determine inhibition kinetics. The in vitro α-amylase and α-glucosidase inhibitory activities of the plant extract were assessed using 3,5-dinitrosalicylic acid (DNS) and p-nitro-phenyl-a-D glucopyranoside (p-NPG) respectively. The results indicated that all plant extracts assayed exhibited better α- glucosidase inhibitory effects than the reference drug(acarbose), as indicated by the higher IC50 (76.10 µg/mL) value of the reference drug, whereas the n-hexane extract of N. sativum seeds gave the best α-amylase effect (IC50 = 35.83 µg/mL). All the extracts exhibited an “uncompetitive” type of inhibition pattern. Our findings hence support the use of these plants in the management of diabetic conditions.
Key words: Nigella sativum, Spondias mombin, Picralima nitilda, α-amylase, α-glucosidase, acarbose
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