Plant-associated hepatogenous photosensitization diseases

Hepatogenous photosensitization of livestock is both economically important and an animal welfare problem in various parts of the world. The condition results when a toxin, whether produced by a higher plant, fungus or alga, causes liver damage or liver dysfunction resulting in retention of the photosensitizing agent phylloerythrin. Phylloerythrin is a metabolic product of chlorophyll produced by rumen microorganisms. Many hepatogenous photosensitization disorders are associated with ingestion of plants containing steroidal saponins. Typical of these diseases is the accumulation of insoluble Ca2+ salts of episarsasapogenin or epismilagenin glucuronides in liver cells and bile ducts. Sporidesmin produced by the fungus Pithomyces chartarum and the pentacyclic triterpene acids lantadene A and B from the plant Lantana camara cause severe problems in some countries. A cyclic hexapeptide produced by the fungus Phomopsis leptostromiformis and cyclic heptapeptides produced by the alga Microcystis aeruginosa are also known to cause hepatogenous photosensitization.