D-1, an organic solvent extractable component of an extract from burn eschar was characterized and the mechanism of its inhibitory effect on mitochondrial respiratory functions was investigated Using silicic acid column chromatography, it was found that D-1 consisted of two parts: a toxic simple lipid and a non-toxic complex lipid. Six subunits were obtained by further silicic add column chromatography, among them, the no. 4 and no. 6 were toxic. Infrared spectrometric studies showed that no. 4 consisted of esters, while no. 6 were peroxides. D-1 also contained large amounts of malonaldehyde (MDA) and lipid hydroperoxides (ROOH). Vitamin E was Found to prevent the inhibitory action of D-1 on mitochondrial function and to reduce the amount of MDA produced. However, if vitamin E was introduced after the addition of D-1, the inhibition could not be prevented although there was still a reduction in MDA production; therefore, MDA per se was probably not the cause of the inhibition. D-1 induced ROOH formation in mitochondrial membranes. Cumene hydroperoxide, an organic hydroperoxide, was capable of inhibiting the mitochondrial function. This inhibitor action was blocked by vitamin E. It is speculated that ROOH in D-1 is probably the element that inhibits mitochondrial function. That D-1 caused lipid peroxidation of membrane lipid was also proved by analysing the fatty add composition of mitochondrial membranes before and after treatment with D-1. It was found that the amounts of polyunsaturated fatty acids decreased and that of saturated fatty acids increased after incubation with D-1, a direct proof that lipid peroxidation has occurred. Lipid peroxidation of the membrane lipid was the result of the action of oxygen free radicals. This process was best shown by a chemiluminescence study. In this experiment, D-1 induced chemiluminescence which was dose-dependently related to the amount of D-1 used. This was probably the most direct proof that D-1 caused lipid peroxidation of membrane lipid resulting in damage of the mitochondria. Copyright (C) 1996 Published by Elsevier Science Ltd for ISBI.
