In vitro and in silico inhibition of angiotensin-converting enzyme by carbohydrates and cyclitols

Fifteen carbohydrates (d-mannose, d-glucose, d-galactose, methyl-alpha-d-glucose, l-rhamnose, d-xylose, d-fructose, d-arabinose, dulcitol, mannitol, beta-maltose, alpha-lactose, melibiose, sucrose, and raffinose) and four cyclitols [l-(+)-bornesitol, myo-inositol, per-O-acetyl-1-l-(+)-bornesitol, and quinic acid] were assayed for in vitro ACE inhibition. Of these molecules, per-O-Acetyl-1-l-(+)-bornesitol, quinic acid, methyl-alpha-d-glucose, d-rhamnose, raffinose, and the disaccharides were determined to be either inactive or weak ACE inhibitors, whereas l-(+)-bornesitol, d-galactose, d-glucose, and myo-inositol exhibited significant ACE inhibition. Molecular docking studies were performed to investigate interactions between active compounds and human ACE (Protein Data Bank, PDB 1O83). The results of various calculations showed that all active sugars bind to the same enzyme region, which is a tunnel directed towards the active site. With the exception of myo-inositol (K (i) = 13.95 mu M, IC50 = 449.2 mu M), the active compounds presented similar K (i) and IC50 values. d-Galactose (K (i) = 19.6 mu M, IC50 = 35.7 mu M) and l-(+)-bornesitol (K (i) = 25.3 mu M, IC50 = 41.4 mu M) were the most active compounds, followed by d-glucose (K (i) = 32.9 mu M, IC50 = 85.7 mu M). Our docking calculations are in agreement with the experimental data and show a new binding region for sugar-like molecules, which may be explored for the development of new ACE inhibitors. (C) 2013 Institute of Chemistry, Slovak Academy of Sciences