Uncompetitive Inhibition of Polyol Pathway Enzymes by Daucus carota Linn. Extract and Management of Diabetes Mellitus

Background: The growing occurrence of complications associated with diabetes calls for the unending exploration of natural products for more efficient therapeutic substances. The polyol pathway is a foundational scheme involved in the development of diabetic complications. Retarding the activities of enzymes in the polyol pathway is, therefore, a potent method of managing these complications. Objective: This work assessed the ability of four non-leafy vegetables, namely Daucus carota Linn. (carrot), Abelmoschus esculentus (L.) Moench (okra), Allium cepa Linn. (onion), and Lycopersicon es-culentum Mill. (tomato), to inhibit the activities of aldose reductase and sorbitol dehydrogenase. Methods: The vegetables’ ability was evaluated by incubating the vegetables with suitable enzymes and substrates. Sample(s) with the lowest inhibitory concentration (IC₅₀) was utilized to determine the mechanism of action of the enzymes by constructing the Lineweaver-Burk graph. Results: Results showed that the aqueous extract of carrot exhibited the lowest IC₅₀ value for the inhibition of both aldose reductase (135.17 µg/mL) and sorbitol dehydrogenase (14.64 µg/mL), respectively. The double reciprocal plot also showed that the aqueous extract of carrot inhibited both aldose reductase and sorbitol dehydrogenase in an uncompetitive fashion. Conclusion: Aqueous extract of carrot successfully retarded the action of polyol pathway enzymes, which may result in the recovery of diabetic complications. This activity may due to the availability of phytochemicals, including carotenoids and phenylacetylenes.