MOLECULAR-STRUCTURES OF 5,6-BENZOFLAVONES AND 7,8-BENZOFLAVONES, INHIBITORS OF ARYL-HYDROCARBON HYDROXYLASE

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (8) , 2774-2784
Abstract
The crystal and molecular structures of 2 isomeric inhibitors of carcinogenesis by certain polycyclic aromatic hydrocarbons are described. The 2 compounds are 7,8-benzoflavone and 5,6-benzoflavone, which are shown by X-ray crystallographic studies to differ appreciably in their 3-dimensional structures. Polycyclic aromatic hydrocarbons are metabolically activated by an enzyme system that is responsible for the detoxification of many chemicals that enter the body. The 2 benzoflavones described here differ in their effect towards specific enzymes in the metabolizing system. Potential energy calculations predict that a nonplanar conformation is most probable for these flavone derivatives, as a result of the presence of a biphenyl-like system. Such a conformation is found for 7,8-benzoflavone with a torsion angle of 23.degree. between the phenyl group and the rest of the molecule. The isomeric 5,6-benzoflavone is a predominantly flat molecule. There is an interaction between O(4) and a neighboring.sbd.C.sbd.H group which may explain the planarity of 5,6-benzoflavone. A comparison is made with the structures of some common carcinogenic polycyclic aromatic hydrocarbons, the activities of which these 2 benzoflavones inhibit.