Screening of the influence of flavonoids on lipoxygenase and cyclooxygenase activity, as well as on nonenzymic lipid oxidation.

Thirty nine flavonoids, isolated from plants, were tested in respect of their influence on soybean lipoxygenase activity, cyclooxygenase activity and inhibition of ascorbic acid-stimulated malonaldehyde formation in liver lipids. Almost all of the tested compounds were antioxidants and stimulated cyclooxygenase when arachidonic acid was used as a substrate at a concentration of 100 microM. Eleven flavonoids were inhibitors of soybean lipoxygenase. A good correlation between the chemical structure and the tested activity was observed. The most active compounds in all tests were luteolin, 6-hydroxyluteolin, nepetin, quercetagetin, patuletin and myricetin.