Cercosporin

Cercosporin is a photosensitizing toxin produced by certain species of the fungus Cercospora, notably Cercospora allii. It is a type of cercosporin, a family of natural products characterized by a specific chemical structure. When exposed to light, cercosporin generates reactive oxygen species, such as singlet oxygen. This photochemical activity is central to its biological effects.

In plants, cercosporin is a well-known phytotoxin, meaning it is toxic to plants. It plays a significant role in plant diseases caused by Cercospora fungi. The photosensitizing action of cercosporin leads to cell membrane damage, chlorophyll degradation, and ultimately, tissue necrosis, manifesting as lesions on the leaves and stems of infected plants. This damage impairs the plant's ability to photosynthesize and can lead to significant yield losses in crops.

The mechanism of action involves cercosporin's ability to absorb light energy, primarily in the blue and red regions of the spectrum. Upon excitation, it transfers this energy to molecular oxygen, producing highly reactive singlet oxygen. This singlet oxygen then attacks cellular components, including lipids and proteins, causing oxidative damage. While primarily known for its phytotoxicity, cercosporin has also been studied for its potential cytotoxic effects on animal cells in laboratory settings. Research continues to explore its biological activities and potential applications or risks.