On the sensitivity to light of polyene fungicides

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Abstract
During recent years various fungicides having a polyene structure have been isolated from streptomycetes. During the study of the action mechanism of a new representative of this group, pimaricin, it was established that the suppression of respiration of yeast by this substance was completely neutralised, if at the same time riboflavin and light were present. The cause of this phenomenon appears to be traceable back to a photodynamic destruction of pimiracin under the influence of riboflavin.The effect is not restricted to riboflavin; some other colouring matters also possess this property. Ascorbic acid and hydroquinone repress the photodynamic reaction greatly. Arguments are presented for supposing that hydroxyl radicals are responsible for the annulment of the polyene group of the fungicide. So far hydrogen peroxide has been regarded as the substance bringing about the photo‐dynamic reactions.