Chemo-Diversity and Secondary Metabolite Content in Corticolous Crustose Lichens (Fam. Arthoniaceae, Graphidaceae, Pyrenulaceae) from Remnants of Colombian Tropical Dry Forests.

内容摘要

Colombia ranks third among South American countries in terms of fungal diversity (including lichens); however, the lichen diversity of tropical dry forest ecosystems, particularly those in the Caribbean region, remains relatively understudied. The typical lichens found in tropical dry forest are crustose/corticolous microlichens (adapted to the xerophytic environments), which produce certain secondary metabolites that act as protective agents against ultraviolet radiation/decomposition/depredators; nonetheless, secondary metabolites of most of these lichens have not yet been described. This study focused on the compositional analysis and the extrolite content of seven lichens: Cryptothecia sp., Cryptothecia scripta, Graphis dendrogramma, Leucodecton occultum, Helminthocarpon leprevostii, Pyrenula ochraceoflava, and Allographa seminuda, using thin-layer chromatography, high-performance liquid chromatography-diode array detector, liquid chromatography-electrospray-mass spectrometry and/or liquid chromatography-tandem mass spectrometry. The main findings were: (i) two Cryptothecia spp. contained 2'-O-methylperlatolic acid (97%) or ovoic/gyrophoric acids (67%/28%); (ii) two specimens of G. dendrogramma had stictic/norstictic acids (33-60%/40%); (iii) three samples of L. occultum were characterized by norstictic acid (42-82%); (iv) schizopeltic/3-O-methylschizopeltic acids (58%/32%) were found in one specimen of H. leprevostii; (v) one sample of P. ochraceoflava was represented by unidentified xanthone-type metabolite/7-chloroemodin/ (26%/24%); and, (vi) the extrolite content in one specimen of A. seminuda was negligible. Finally, 10 of the 11 lichen specimens studied from the Department of Atlántico within Colombia contained certain secondary metabolites that likely reflect the common types of extrolites, namely, di-/tri-depsides, depsidones, dibenzofurans, and chlorinated anthraquinones/xanthones, which could be hypothetically related to the evolutionary patterns of this type of organism.