Amide alkaloids characterization and neuroprotective properties of Piper nigrum L.: A comparative study with fruits, pericarp, stalks and leaves

•42 amide alkaloids were identified and characterized by UHPLC-LTQ-Orbitrap HRMS.•8 amide alkaloids were firstly reported in P. nigrum.•9 constituents in different parts of P. nigrum were determined by UHPSFC-MS.•The extracts of different parts of P. nigrum showed neuroprotective effects in vitro.