Photodynamic activity of 4-nitroquinoline-1-oxide and related compounds

Photosensitizing properties of quinine and synthetic antimalarials

Quinine, an alkaloid that occurs in the bark of trees of the genus Cinchona, has been used for the treatment of malaria in humans for over 150 years. In 1888 it was reported that quinine was more toxic to plant tissues and frog eggs in the light than in the dark; thus it is probably one of the first pure compounds shown to be a photosensitizer for biological systems. During this century, because of the toxic side effects of quinine and the appearance of quinine-resistant malarial strains, a search was begun to identify synthetic antimalarial compounds with improved properties. A number have been identified and are now in widespread use; but like quinine, most of these are also photosensitizers. Because of the very large numbers of patients receiving antimalarials, many studies have been made of the photophysical, photochemical and photosensitizing properties of quinine and several of the most commonly used synthetic antimalarials (chloroquine, primaquine, quinacrine and mefloquine). The results of these studies are summarized in this review. Most antimalarials photosensitize in part by the generation of singlet oxygen, although free radical pathways may also be involved. The carcinogenic and photocarcinogenic properties of antimalarials and related compounds are briefly surveyed.

Classification of chemical agents as to their ability to induce long- or short-patch DNA repair in human cells

33 chemical agents and UV- and gamma-irradiation were tested for their comparative ability to induce long-patch or short-patch repair using the 5-bromodeoxy-uridine photolysis assay. For 11 chemical agents repair was long-patch in nature as determined by calculated patch size and response of xeroderma pigmentosum cells relative to normal human cells. Typical patch sizes as measured by this assay were about 90 nucleotides for UV repair, a range of 30 to 70 nucleotides for a variety of known and suspected UV-mimetic chemicals, and 3-4 nucleotides for gamma-radiation. Alkylating agents previously shown to induce short-patch repair were shown also to induce long-patch repair.

Herpes virus inactivation by chemical carcinogens: differential inactivation of herpes simplex viruses by 4-nitroquinoline 1-oxide and related compounds

Treatment of stocks of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) with the chemical carcinogen 4-nitroquinoline 1-oxide (NQO) resulted in inactivation of virus infectivity at rates which were directly dependent on the concentration of NQO and interval of exposure to NQO. HSV-1 strains were more sensitive than HSV-2 strains to inactivation by NQO, although survival curves of both HSV types were multicomponent. Exposure of HSV-2 to a related group of chemicals suggested that the structural specificity required for inactivation of this virus was similar to that established by previous in vivo carcinogenicity tests.