In silico and in vitro analysis reveal multi-target anti-hyperglycaemic properties of gedunin, a limonoid from neem ( Azadirachta indica )

Insulin secretion and insulin related pathways have been the prime targets in the treatment of diabetes for a long time. However, recently a lot of attention is being directed towards addressing hyperglycaemia as the main perpetrator of the symptoms in this metabolic disorder. This new treatment approach also involves greater inclination to plant derived therapeutic agents for their safety and probable minimal side effects. The objective of the present study was to scientifically elucidate the potential of gedunin (a limonoid from Neem tree) as an anti-hyperglycaemic agent. The effect of gedunin on pancreatic and salivary amylase activity and glucose transport across yeast cell membrane was tested at three different concentrations (5 μM, 10 μM and 20 μM) using known inhibitor acarbose as the standard. Multiple Ligand Simultaneous Docking was used to study the interaction of gedunin with salivary and pancreatic amylase and determine binding affinity and specificity of this interaction. The in vitro results documented a steady, linear pancreatic alpha amylase (ovine) inhibition in a concentration dependent manner with gedunin showing lower IC50 value of 20.25 μM against acarbose (IC50 = 31.12 μM) a known enzyme inhibitor used as standard in the present study. The inhibition of salivary amylase by gedunin was also distinct. Yeast cell glucose uptake studies revealed remarkable inhibition of glucose absorption at 10 μM and 20 μM concentration of gedunin (5.45% and 13.87% respectively with respect to control). Corroborating the in vitro findings even in the docking studies gedunin exhibited higher docking score (− 8.12 Kcal/mol) and higher enzyme inhibition potency (Ki = 1.12 μM) with human pancreatic amylase-substrate complex as compared to acarbose (docking score-5.24 Kcal/mol, Ki = 110.8 μM). The studies further suggested a non-competitive, mixed kind of inhibition by gedunin. As evident from this current in vitro study, gedunin had shown significant inhibition of alpha amylases and glucose uptake at much lower concentration (5, 10 and 20 μM) than previous studies where the concentrations used were (20.7–124.3 μM). This study lays strong evidence to the rationale of gedunin being an important lead compound to developing a promising hyperglycaemic agent, simultaneously targeting glucose absorption in the intestine and enzymatic digestion of polysaccharides.