Abstract
When administered as drugs or consumed as food components, polyphenolic compounds synthesised in plants interfere with intracellular signal transduction pathways, including pathways of nitric oxide (NO) synthase (NOS) expression. However, the effects of these compounds in vivo do not always correlate with NOS-inhibiting activities, as revealed in experiments with cultured cells. The goal of this work was to compare the effects of resveratrol, ellagic acid and ipriflavone on NO production in rat organs measured by means of ESR spectroscopy. All of the above compounds are known as inhibitors of iNOS expression. The presumed ability to decrease NO production was manifested only by ellagic acid; it decreased NO production in spleen of intact rats. Iproflavone and resveratrol even enhanced the lipopolyssacharides (LPS)-induced increase of NO production. Ipriflavone increased NO production in the brain cortex, cerebellum, liver, heart, kidneys, blood, lungs and skeletal muscles. Resveratrol produced a similar effect in all of the above organs, except kidneys, lungs and muscles. Taken together, our results suggest that modifications of NO level in tissues by a natural compound cannot be predicted from data about its effects on NOS expression or activity. This stresses the importance of direct measurements of NO in tissues.