(R)-Bromoenol lactone-d7 ((R)-BEL-d7) contains seven deuterium atoms at the 2, 3, 4, 5, 6, 7, and 8 positions. It is intended for use as an internal standard for the quantification of (R)-BEL by GC- or LC-mass spectrometry (MS). The phospholipases are an extensive family of lipid hydrolases that function in cell signaling, digestion, membrane remodeling, and as venom components. The calcium-independent phospholipase A2 (iPLA2) are a PLA2 subfamily closely associated with the release of arachidonic acid in response to physiologic stimuli. (R)-Bromoenol lactone ((R)-BEL) is an irreversible, chiral, mechanism-based inhibitor of iPLA2γ. Unlike (S)-BEL, (R)-BEL does not inhibit iPLA2β except at high doses of 20-30 µM. (R)-BEL inhibits human recombinant iPLA2γ with an IC50 of approximately 0.6 µM.