Thioester analogs of glycerophospholipids, in combination with Ellman's reagent, are convenient colorimetric substrates for the measurement of phospholipase activity. HEPC is a truncated analog of phosphatidylcholine with the entire sn-1 substituent deleted, and with a hexadecylthioester in the sn-2 position. HEPC is a substrate for Type II phospholipase A2 (PLA2) enzymes, such as porcine pancreatic, bee venom, and snake venom PLA2. The intrinsic biological activity of HEPC has not been actively investigated.