Laurus nobilis Linn. Inhibits Polyol Pathway Enzymes: Strategy for Managing Diabetic Complications

The rising incidence of diabetic complications necessitate the continuous search for safer, cheaper and effective pharmacological agents. Polyol pathway is an underlying process implicated in the pathogenesis of diabetic complications. Inhibition of enzymes in the polyol pathway is a veritable means of ameliorating diabetic complications. This study evaluated the inhibitory potential of some spicy plants on the activities of polyol pathway enzymes (aldose reductase and sorbitol dehydrogenase). Aqueous extracts of Laurus nobilis (bay), Cinnamomum zeylanicum (cinnamon), Murraya koenigii (curry), Thymus vulgaris (thyme) and Curcuma longa (turmeric) were incubated with appropriate enzymes and substrates, and percentages inhibition determined. Results showed that bay extract had effective IC50 for inhibition of both aldose reductase (174.87 µg/mL) and sorbitol dehydrogenase (37.08 µg/mL). It also revealed that bay extract inhibited aldose reductase and sorbitol dehydrogenase in a non-competitive and competitive manner respectively. It is therefore concluded that bay extract effectively inhibited activities of polyol pathway enzymes, and may contribute to the amelioration of diabetic complications.