Active oxygen forms in photoreaction between DNA and furanochromones khellin and visnagin

The two furanochromones khellin and visnagin react with DNA under irradiation by 365 nm light, forming photoadducts. Recently, the use of khellin as therapeutic agent for skin diseases has been proposed. It is well known that during the formation of photoadducts toxic active oxygen forms are produced. We studied therefore the behaviour of the two furanochromones as producers of 1O-2 and O-2. Our results indicate that visnagin is a strong generator of both superoxide radicals and singlet oxygen, while khellin does not exhibit strong production of OO-2, which is promptly quenched by superoxide dismutase.