Abstract
Nitric esters are among the compounds that can liberate nitrogen monoxide (NO) in the organism. Due to the vasodilatation caused by nitrogen monoxide, NO-donors have been shown to protect endothelial function, acting as vasodilators, promoting efficient oxygen supply to tissues, to lower blood pressure, and to inhibit platelet aggregation. Incorporation of a NO-liberating moiety in the structure of non-steroidal anti-inflammatory drugs results in anti-inflammatory agents that are safer for the gastrointestinal system. In this research, ibuprofen and naproxen, two commonly applied non-steroidal anti-inflammatory drugs (NSAID), non-selective inhibitors of cyclooxygenases, were used to design novel anti-inflammatory agents able to release NO in the organism. Thus, the NSAIDs were amidated with beta-alanine and L-proline, which were able to incorporate the 2-nitro-oxyethyl moiety as the NO donor. The resulting compounds were anti-inflammatory agents, found to be more potent than the mother drugs, demonstrating remarkable inhibition of cyclooxygenase-2 over cyclooxygenase-1 and the ability to release NO in vitro. Furthermore, two of the most active anti-inflammatory compounds proved to be effective hypolipidemic agents, decreasing plasma total cholesterol, triglycerides, and LDL-cholesterol in hyperlipidemic rats significantly. The most effective compound in all the above tests was the ibuprofen derivative 5, which inhibited COX-2 by 95%, decreased inflammation by 73%, and reduced all lipidemic indices by more than 50%. Furthermore, docking experiments of compound 5 on the active sites of COX-1 and COX-2 showed that it interacts intensely with the binding site of COX-2, and the binding energy is equivalent to that of the relevant to celecoxib selective COX-2 inhibitor 4-[5-(4-bromophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl] benzenesulfonamide (SC-5580). In conclusion, the performed structural modifications resulted not only in the improvement of the anti-inflammatory activity, compared with the parent NSAID, but also acquired strong hypolipidemic activity. Thus, the combination of structural characteristics resulting in a decrease in lipidemia, with possible inhibition of atherosclerosis, due to their anti-inflammatory activity and vasodilatation ability, via the liberated NO, may constitute a useful rationale for new compounds.