Studies on high-energy collision-induced dissociation of endogenous cannabinoids: 2-arachidonoylglycerol and n-arachidonoylethanolamide in FAB-mass spectrometry.
Analysis of 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamide (anandamide) via alkali or alkaline earth metal-adduct high-energy collision-induced dissociation (CID) in fast-atom bombardment (FAB) ionization-mass spectrometry (MS) is described. The CID-MS/MS of the [2-AG+Li](+) or [2-AG+Na](+) ion undergoes charge-remote fragmentation (CRF), which is useful for the determination of the double-bond positions in the hydrocarbon chain, while the CID-MS/MS of the [2-AG-H+Cat](+) (Cat = Mg(2+), Ca(2+), Ba(2+)) ion provides an abundant fragment ion of the cationized arachidonic acid species, which is derived from cleaving the ester bond via a McLafferty-type rearrangement in addition to structurally informative CRF ions in small amounts. On the other hand, the CID-MS/MS spectra of anandamide cationized with both alkali metal (Li(+) or Na(+)) and alkaline earth metal (Mg(2+), Ca(2+), or Ba(2+)) show CRF patterns: the spectra obtained in lithium or sodium adduct are more clearly visible than those in magnesium, calcium, or barium adduct. The McLafferty rearrangement is not observed with metal-adduct anandamide. The characteristics in each mass spectrum are useful for the detection of these endogenous ligands. m-Nitrobenzyl alcohol (m-NBA) is the most suitable matrix. A lithium-adduct [2-AG+Li](+) or [anandamide+Li](+) ion is observed to be the most abundant in each mass spectrum, since the affinity of lithium for m-NBA is lower than that for other matrices examined.
Kasai
Hiroko F
HF
Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa, Tokyo 142-8501, Japan. kasai@hoshi.ac.jp
Tsubuki
Masayoshi
M
Honda
Toshio
T
D001095:Arachidonic Acids / Q000032:analysis*; D002186:Cannabinoids / Q000737:chemistry*; D063388:Endocannabinoids; D005989:Glycerides / Q000032:analysis*; D007700:Kinetics; D008672:Metals, Alkali / Q000737:chemistry*; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D015394:Molecular Structure; D053284:Polyunsaturated Alkamides / Q000032:analysis*; D012680:Sensitivity and Specificity; D016339:Spectrometry, Mass, Fast Atom Bombardment / Q000379:methods*
D001095:Arachidonic Acids; D002186:Cannabinoids; D063388:Endocannabinoids; D005989:Glycerides; D008672:Metals, Alkali; D008673:Metals, Alkaline Earth; D053284:Polyunsaturated Alkamides; C094503:glyceryl 2-arachidonate; C078814:anandamide