Quercetin from Parinari curatellifolia planch.ex benth differentially regulates Drosophila insulin-like peptides II and V in hyperglycaemic flies

Parinari curatellifolia Planch.ex Benth is utilised for the treatment of diabetes in Sub-Saharan Africa. However, the molecular mechanism of action and bioactive compounds are not fully known. While the current management of diabetes is efficacious, limitations still exist. The purpose of this study is to characterise the hypoglycaemic principle(s) of Parinari curatellifolia (PC) and its mechanism in Drosophila insulin-like peptide (DILP) gene expression. The solvent fractions from the leaf of PC were evaluated for hypoglycaemic effects and compared with metformin and glibenclamide (standard drugs) in type 2 diabetic Drosophila melanogaster (DM). We used column chromatography and gel-filtration techniques to obtain a pure sample. Bruker AVANCE-II+ 600 MHz and AVANCE NEO 800 MHz NMR spectrometers were used to characterise the pure compound. The samples were run in duplicate for DILP2, DILP3, and DILP5 gene expression on BioRAD CFX96 RealTime PCR. Ethyl acetate fraction was as effective as metformin and glibenclamide in reducing the hyperglycaemic state in diabetic flies and a 50 % decrease (p < 0.05) in the glucose compared to the diabetic untreated (DU) control flies. The bioactive compounds of PC exhibit a 40 % and 70 % increase (p < 0.05) in DILP2 and DILP5 gene expression, respectively. The pure sample was characterized, and designated as Quercetin, a flavonol with molecular formula C₁₅H₁₀O₇. Quercetin from the leaf of P. curatellifola exhibits hypoglycaemic effects and increased DILP2 and DILP5 gene expression in diabetic DM like metformin and glibenclamide antidiabetics. This insight could guide drug development in the management of type 2 diabetes.