An adaptation of the Candida albicans phototoxicity test to demonstrate photosensitizer action spectra.

The Candida albicans assay is widely used for the testing of potential photosensitizers, especially furocoumarins. A novel adaptation of this assay is described which provides a rapid, inexpensive and easy-to-perform method of producing action spectra. The use of filter paper rectangles with central apertures instead of the usual discs, and monochromatic irradiation with a liquid light guide reduces some of the problems associated with the standard assay. Action spectra for 8-methoxypsoralen and a new pyrrolocoumarin derivative are presented as illustrative examples.