Effects of 6-(10-Hydroxydecyl)-2, 3-dimethoxy-5-methyl-1, 4-benzoquinone (Idebenone) and Related Benzoquinones on Porcine Pancreas Phospholipase A2 Activity

6-(10-Hydroxydecyl)-2, 3-dimethoxy-5-methyl-1, 4-benzoquinone (idebenone) has been found to have a membrane-stabilizing activity in studies using lysosomes. Using dimyristoyl L-α-phosphatidylcholine (DMPC) as a substrate, the effects of idebenone and related benzoquinones on phospholipid digestion by phospholipase A2 (PLA2) was investigated. Free myristic acid, released from DMPC upon PLA2 treatment, was anthrylmethylated with 9-anthryldiazomethane (ADAM) and determined by reversed-phase HPLC. Idebenone and a related benzoquinone, 2, 3-dimethoxy-5-methyl-6-(10-morpholinodecyl)-1, 4-benzoquinone hydrochloride (QS-10·Mor), inhibited the hydrolysis of the substrate with PLA2 in a dose-dependent manner. It is suggested that the effect of idebenone on PLA2, in addition to its antioxidant activity against lipid peroxidation, can be attributed to membrane-stabilizing activity.