Gedunin and Azadiradione: Human Pancreatic Alpha-Amylase Inhibiting Limonoids from Neem (Azadirachta indica) as Anti-Diabetic Agents

Abstract

Human pancreatic α-amylase (HPA) inhibitors offer an effective strategy to lower postprandial hyperglycemia via control of starch breakdown. Limonoids from Azadirachta indica known for their therapeutic potential were screened for pancreatic α-amylase inhibition, a known anti-diabetic target. Studies were carried out to reveal their mode of action so as to justify their hypoglycemic potential. Of the nine limonoids isolated/semi-synthesized from A.indica and screened for α-amylase inhibition, azadiradione and exhibited potential inhibition with an IC50 value of 74.17 and 68.38 μM, respectively against HPA under in vitro conditions. Further screening on AR42J α-amylase secretory cell line for cytotoxicity and bioactivity revealed that azadiradione and gedunin exhibited cytotoxicity with IC50 of 11.1 and 13.4μM. Maximal secreted α-amylase inhibition of 41.8% and 53.4% was seen at 3.5 and 3.3μM, respectively. Michaelis-Menten kinetics suggested a mixed mode of inhibition with maltopentaose (K i 42.2, 18.6 μM) and starch (K i ′ 75.8, 37.4 μM) as substrate with a stiochiometry of 1:1 for both azadiradione and gedunin, respectively. The molecular docking simulation indicated plausible π-alkyl and alkyl-alkyl interactions between the aromatic amino acids and inhibitors. Fluorescence and CD confirmed the involvement of tryptophan and tyrosine in ligand binding to HPA. Thermodynamic parameters suggested that binding is enthalpically and entropically driven with ΔG° of -21.25 kJ mol-1 and -21.16 kJ mol-1 for azadiradione and gedunin, respectively. Thus, the limonoids azadiradione and gedunin could bind and inactivate HPA (anti-diabetic target) and may prove to be lead drug candidates to reduce/control post-prandial hyperglycemia.

Gedunin- and Khivorin-Derivatives Are Small-Molecule Partial Agonists for Adhesion G Protein-Coupled Receptors GPR56/ADGRG1 and GPR114/ADGRG5

“…The final version may differ from this version. 2012; Hieronymus et al, 2006;Ponnusamy et al, 2015). Gedunins and structurallyrelated khivorins may have multiple molecular targets, but encouragingly, Neem tree extracts and/or enriched compound mixtures have been found to be generally safe for human use and may be viable options for therapeutic development (Biswas et al, 2002).…”

Rational in silico design of novel α-glucosidase inhibitory peptides and in vitro evaluation of promising candidates

“…α-Amylase (α-1,4-glucan-4-glucanohydrolase, E.C. 3.2.1.1) catalyses the initial step of starch hydrolysis to maltose, while α-glucosidase, a membrane-bound enzyme in the epithelial mucosa of the small intestine, catalyses the hydrolysis of maltose and other disaccharides to release free glucose molecules [5,6]. Thus, inhibitors targeting these enzymes ultimately impede the uptake of glucose from complex dietary carbohydrates into the blood circulation, thereby effectively diminishing postprandial hyperglycemia.…”

Biological Activities of Gedunin—A Limonoid from the Meliaceae Family

“…Thus, HPA inhibitors present an effective strategy to lower postprandial hyperglycemia by controlling starch breakdown [61]. Recently, neem limonoids, including gedunin, were screened and identified as potent inhibitors of HPA, based on their inhibition potency and in vitro cytotoxicity, and studied in order to identified their mode of action and underlying molecular interactions [62]. In this study, gedunin presented promising results as an HPA inhibitor.…”