Electrospray ionization mass spectrometric method for the determination ofcannabinoid precursors: N-acylethanolamine phospholipids (NAPEs)

N-Acylethanolamine phospholipids (NAPEs) serve as endogenous precursors of N-acylethanolamines (NAEs), e.g. N -arachidonoylethanolamine (anandamide) a nd N -palmitoylethanolamine that are endogenous ligands of cannabinoid rece ptors, Under physiological conditions, NAPE is found in very low concentrat ions in mammalian tissue (3-12 nmol g(-1)). However, pathophysiological con ditions may increase the endogenous NAPE levels, which again may cause an i ncrease in endocannabinoid concentrations. This paper presents a simple and selective method for the determination of NAPE standards using negative el ectrospray ionization mass spectrometry (ESI-MS). The procedure provides co mplete positioning of all acyl and alkenyl groups contained in each NAPE sp ecies. The calibration curve for standard NAPE was linear over the range 10 0 fmol-50 pmol (0.1-50 ng) per injection. The lower limit of detection (sig nal-to-noise ratio of 3) was 100 fmol, implying that this method is superio r to previous methods for the determination of NAPE. These results suggest that this ESI-MS method can be used to identify and quantify NAPE species i n mammalian tissues and provide information on the corresponding NAEs to be released from the endogenous NAPE pool. Copyright (C) 1999 John Wiley & So ns, Ltd.