INHIBITION OF SUCCINOXIDASE BY THE VITAMIN P-LIKE FLAVONOID 2',3,4-TRIHYDROXY CHALCONE

¹ Scripps Metabolic Clinic, La Jolla, Calif.

2',3,4-trihydroxy chalcone gives a strong inhibition of rat liver succinoxidase, an effect which is greater with increasing pH. At a pH of 7.4, 1 x 10^-4 M chalcone almost completely inhibits the enzyme.

The chalcone reacts with substrate activating dehydrogenase and not with the cytochrome c-cytochrome oxidase system.

The methoxy derivative, 3-methoxy-2',4-dihydroxy chalcone, is not toxic to the succinoxidase system.

The inhibition is probably due to a combination of quinoid oxidation product of the flavone with essential SH groups of the enzyme. The reaction can be prevented but not reversed by glutathione.

Although the flavone forms complexes with various metals, including copper, it did not decrease the cupric ion inhibition of the succinoxidase.