title: Studies on the photobiological activity of two naturally occurring furochromones, visnagin and khellin, in Chlamydomonas reinhardtii.
abstract: Irradiation of arg-1 cells of the green alga Chlamydomonas reinhardtii with UV-A in the presence of visnagin (10 microg/ml) produced weak mutagenic effects when a fluence rate of 5.1 W/m2 and fluences of 1.5-36.7 kJ/m2 were applied. A maximum number of revertants was obtained at approximately 9.2 kJ/m2. When a fluence rate of 20.4 W/m2 was used the photomutagenicity of visnagin was markedly enhanced with fluences of > or = 36.7 kJ/m2. In survival experiments with a fluence rate of 5.1 W/m2 the surviving fraction decreased continuously to approximately 4%. In experiments with a fluence rate of 20.4 W/m2, however, higher survival rates were observed compared at equal UV-A doses. Visnagin was much less phototoxic and photomutagenic than bergapten when compared at equimolar concentrations and equal UV-A doses. Re-irradiation with UV-A in the absence of unbound visnagin did not alter survival and mutagenicity which had been induced by the first treatment. The mutation frequency plotted versus the UV-A fluence exhibited second-order kinetics. Khellin showed only marginal photosensitizing capacity and no significant mutagenicity up to a concentration of 100 microg/ml and a total UV-A fluence of 73.4 kJ/m2.
authors.affiliation: Institut fúr Botanik und Pharmazeutische Biologie der Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Schimmer
mesh_terms: D000078223:5-Methoxypsoralen; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D007666:Khellin / Q000031:analogs & derivatives* / Q000633:toxicity*; D008730:Methoxsalen / Q000031:analogs & derivatives / Q000633:toxicity; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D018462:Photobiology; D017319:Photosensitizing Agents / Q000633:toxicity*; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D009153:Mutagens; D017319:Photosensitizing Agents; D000078223:5-Methoxypsoralen; D007666:Khellin; C044999:visnagin; D008730:Methoxsalen