Prostaglandin F2α-1-glyceryl ester-d5 (PGF2α-1-glyceryl ester-d5) is intended for use as an internal standard for the quantification of PGF2α-1-glyceryl ester by GC- or LC-MS. 2-Arachidonoyl glycerol (2-AG) has been isolated from porcine brain, and has been characterized as the natural endocannabinoid ligand for the central cannabinoid receptor.1,2 Incubation of 2-AG with cyclooxygenase 2 and specific PGH2 isomerases in cell cultures and isolated enzyme preparations results in PG glyceryl ester formation.3 The biosynthesis of PGH, PGD, PGE, PGF, and thromboxane A-2-glyceryl ester compounds have all been documented. The 2-glyceryl ester moiety equilibrates rapidly (within minutes) with the more stable 1-glyceryl ester, producing a 10:90 2:1-glyceryl ester mixture in typical aqueous media. While the stability and metabolism of PGF2α-1-glyceryl ester has been investigated, little is known about its intrinsic biological activity.4WARNING This product is not for human or veterinary use.