Wiktionary
n. (context organic compound English) An acid found in some lichens.
Wikipedia
Secalonic acids A, B, and C, are chiral dimeric tetrahydroxanthones closely related to ergoflavin and ergochrysin A that are collectively called ergochromes and belong to a class of mycotoxins initially isolated as major ergot pigments from the fungi Claviceps purpurea that grows parasitically on rye grasses. From early times and particularly in medieval Europe the consumption of grains containing ergot has repeatedly lead to mass poisonings known as ergotism which was caused by toxic ergot alkaloids and mycotoxins such as the ergochromes, due to contamination of flour by C. purpurea. Secalonic acid D the enantiomer of secalonic acid A is a major environmental toxin, isolated from the fungus Penicillium oxalicum, and is a major microbial contaminant of freshly-harvested corn which causes toxicity through contamination of foodstuffs.
acid A or ergochrome AA.svg|Secalonic acid A acid B or ergochrome BB.svg|Secalonic acid B acid C or ergochrome AB.svg|Secalonic acid C acid D or ergochrome EE.svg|Secalonic acid D |Ergoflavin A.svg|Ergochrysin A