Chemical variation in the lichen genus Letrouitia (Ascomycota,Letrouitiaceae)

Secondary metabolites from 193 specimens belonging to 15 species of Letrouitia were analyzed by HPLC. Significant quantities of the anthraquinones parietin and fragilin were found in most species and occasionally minor quantities of emodin, 5-chloroemodin, 7-chloroemodin, 7-chloroteloschistin, 7-chlorofallacinal and 7-chloroparietinic acid were present. Eight previously unknown lichen substances were identified. A chemotype containing seven new dibenzofurans (8-chlorodioxocondidymic acid, 8-chlorodioxodidymic acid, 8-chloroxodidymic acid, dioxocondidymic acid, dioxodidymic acid, letrouitic acid and oxodidymic acid) was found in 3 species. In addition, a chemotype containing four unknowns (possibly chlorodepsidones) occurred in L. subvulpina. Eight different chemotypes were identified in the genus. The secondary chemistry was important for the precise identification of some species in Letrouitia. The similarity in secondary chemistry between Letrouitiaceae and Teloschistaceae is not particularly strong, as the shared compounds are also known to occur in several other lichen families.