Design and synthesis of new carbamates as inhibitors for fatty acid amide hydrolase and cholinesterases: Molecular dynamic, in vitro and in vivo studies.

Abstract As anandamide (N-arachidonoylethanolamine, AEA) shows neuroprotective effects, the inhibition of its degradative enzyme, fatty acid amide hydrolase (FAAH) has been considered as a hopeful avenue for the treatment of neurodegenerative diseases, like Alzheimer’s disease (AD). Memory loss, cognitive impairment and diminution of the cholinergic tone, due to the dying cholinergic neurons in the basal forebrain, are common hallmarks in patients with AD. By taking advantage of cholinesterase inhibitors (ChEIs), the degradation of acetylcholine (ACh) is decreased leading to enhanced cholinergic neurotransmission in the aforementioned region and ultimately improves the clinical condition of AD patients. In this work, new carbamates were designed as inhibitors of FAAH and cholinestrases (ChEs) (acetylcholinestrase (AChE), butyrylcholinestrase (BuChE)) inspired by the structure of the native substrates, structure of active sites and the SARs of the well-known inhibitors of these enzymes. All the designed compounds were synthesized using different reactions. All the target compounds were tested for their inhibitory activity against FAAH and ChEs by employing the Cayman assay kit and Elman method respectively. Generally, compounds possessing aminomethyl phenyl linker was more potent compared to their corresponding compounds possessing piperazinyl ethyl linker. The inhibitory potential of the compounds 3a-q extended from 0.83±0.03 μM (3i) to ˃100 μM (3a) for FAAH, 0.39±0.02 μM (3i) to 24% inhibition in 113±4.8 μM (3b) for AChE, and 1.8 ±3.2 μM (3i) to 23.2 ±0.2 μM (3b) for BuChE. Compound 3i a heptyl carbamate analog possessing 2-oxo-1,2-dihydroquinolin ring and aminomethyl phenyl linker showed the most inhibitory activity against three enzymes. Also, compound 3i was investigated for memory improvement using the Morris water maze test in which the compound showed better memory improvement at 10 mg/kg compared to reference drug rivastigmine at 2.5 mg/kg. Molecular docking and molecular dynamic studies of compound 3i into the enzymes displayed the possible interactions of key residues of the active sites with compound 3i. Finally, kinetic study indicated that 3i inhibits AChE through the mixed- mode mechanism and non-competitive inhibition mechanism was revealed for BuChE.