Uncoupling effect of anacardic acids from cashew nut shell oil on oxidative phosphorylation of rat liver mitochondria

Anacardic acids are one of natural products found in not only the cashew nu t shell oil but also the nut and fruit juice. The present study was conduct ed to investigate the uncoupling effect of anacardic acids on oxidative pho sphorylation of rat liver mitochondria using succinate (plus rotenone) as a substrate. Four anacardic acids with C15:0, C15:1, C15:2 or C15:3 as an al kyl side chain exhibited uncoupling effects similar to the classical uncoup ler, 2,4-dinitrophenol on ADP/O ratio, state 4 and respiratory control rati o (RCR). Anacardic acid with C15:1 side chain was most effective for uncoup ling of these compounds. Salicylic acid, which has no alkyl side chain, exh ibited a very weak uncoupling effect on oxidative phosphorylation. When the carboxyl group in anacardic acids was lost converting them to the correspo nding cardanols, uncoupling activity dramatically decreased regardless of t he number of double bonds in the long alkyl chain. These results suggest th at the C15 alkyl side chain as well as the carboxyl group may play an impor tant role in assisting the uncoupling activity of anacardic acids in liver mitochondria of animals. This study provides the first evidence of an uncou pling effect of anacardic acids on liver mitochondria.