Anticholinesterases and antioxidant alkamides from Piper nigrum fruits.

The anticholinesterase and antioxidant effects of five different extracts of Piper nigrum were evaluated. Twenty-one known alkamides were isolated from active ethyl acetate extract and investigated for their cholinesterase inhibitory and antioxidant effects. Among them, piperine (2), piperettine (5) and piperettyline (20) exhibited dual inhibition against AChE and BChE, and feruperine (18) was the most potent selective inhibitor of BChE. Molecular docking simulation was performed to get insight into the binding interactions of the ligands and enzymes. In addition, N-trans-feruloyltyramine (3) contributed to the strongest DPPH radical-scavenging activity. The self-induced Aβ aggregation inhibition of 2, 5 and 18 was further evaluated. Results indicated that some alkamides could be multifunctional lead candidates for Alzheimer's disease therapy.