Antidiabetic effect of Tryptophan, Nuciferin, and isoquercetin in Lotus rhizome

Abstract

The antidiabetic property of Nelumbo nucifera rhizome, a medicinal food used to manage diabetes mellitus in Sri Lankan native medicine has not been scientifically explained yet. The Lotus rhizome is found to compose several medicinally active compounds with anti-diabetic properties, including Betulinic acid, Tryptophan, Nuciferin, isoquercetin, Rutin, β- Sitosterol, Stigmasterol, and Fibre.  A narrator review was conducted to identify the scientific basis of the antidiabetic property with the explanation of the molecular level mechanisms of glucose homeostasis of these medicinally active components. This article reviews the bio-physiological mechanisms of glucose homeostasis by Tryptophan, Nuciferin, and isoquercetin A literature search was done in PubMed and Google Scholar databases using different combinations of the search terms “Nelumbo nucifera rhizome”, “Lotus rhizome”, “phytochemicals”, “antidiabetic effect”, “hypoglycaemic effect”, “Tryptophan”, “Nuciferin”, “isoquercetin” and “molecular mechanism”. Tryptophan is found to reduce blood glucose levels via five identified mechanisms, namely, inhibiting intestinal glucose absorption, inhibiting liver gluconeogenesis, improving insulin resistance, increasing insulin secretion in the pancreas, and enhancing glucose uptake in adipocytes. Nuciferin can improve blood glucose by stimulating the closure of Adenosine Triphosphate dependent potassium (K-ATP) channels and triggering insulin release. Isoquercetin can inhibit α-glucosidase in the small intestine and regulate the expression of mRNA which codes insulin resulting in increased insulin release. This review explains to the medical practitioners of various medical practices the scientific basis of the antidiabetic effect of lotus rhizome allowing them to utilize it as a medicinal food for the benefit of diabetic patients under their care.