Lichens and spore-derived cultured mycobionts of Teloschistes chrysophthalmus and Ramalina celastri were studied chemically, and results indicated that they produced, respectively, parietin and usnic acid as major secondary metabolites, which were purified and identified. Identification of the compounds was performed by high performance liquid chromatography and structural elucidation by nuclear magnetic resonance (1H) and electron impact mass spectrometry. Usnic acid exhibited antiviral activity whereas parietin had a virucidal effect against the arenaviruses Junín and Tacaribe

A strain of the lichen mycobiont isolated from a thallus of Parmotrema reticulatum was cultured axenically on different media. The morphology, anatomy, growth of the colonies, and metabolite production were studied. The isolated fungal colonies developed well and showed a remarkable morphogenetic capacity on most of the assayed solid media, e.g., malt extract 2%-yeast extract 0.2% (MEYE), malt extract 1%-yeast extract 0.4%-sucrose 10% (MY10), and the original Lilly & Barnett medium (LB). The identity of the isolated fungus was confirmed by its ITS rDNA-sequence. Atranorin, the major cortical lichen depside, was produced when the colonies were grown over 5 and 10 months on solid LB medium, combined with a dessication treatment. Atranorin was identified by matching of UV spectra obtained from HPLC running and a reference substance in a spectrum library. Colonies grown on MEYE and MY10 with a dessication treatment did not produce any lichen secondary metabolite. Mycobionts grown for 5 months on solid MEYE without a dessication treatment produced triacylglycerides as the major metabolites, and the fatty acids were characterized as their methyl esters. Analysis by TLC and HPLC-DAD of extracts of colonies grown on LB and MY10 without dessication revealed that the typical secondary compounds of the natural lichen were not produced. The major metabolites of the natural lichen thallus were identified by chromatographic and spectroscopic methods.

Two new fernene triterpenoids, fern-9(11)-en-3,19-dione (1) and 3β-acetoxyfern-9(11)-en-19-one (2), together with the known 3β-acetoxyfern-9(11)-en-19β-ol (3) and lichexanthone (4), have been isolated from the acetone extract of the lichen Pyxine berteriana. The structures of the new compounds were established on the basis of IR, extensive 1D and 2D NMR, and MS analyses. Although several fern-9(11)-enes have been isolated from lichens, compounds 1 and 2 are the first examples of naturally occurring fernene triterpenoids with a carbonyl function at C-19.Lichens are symbiotic associations composed of at least a fungal partner, the mycobiont, and a photosynthetic partner, the photobiont. 1 These associations frequently produce characteristic secondary metabolites that are of fungal origin. Most are unique to lichens, and only a small number occur in non-lichenized fungi or higher plants. 2 Many of these lichen secondary compounds exhibit antibiotic, antitumor, antimutagenic, allergenic, antifungal, antiviral, enzyme inhibitory, and plant growth inhibitory properties. 2,3 Triterpenoids are widely distributed in lichens, being commonly present in genera such as Nephroma and Pseudocyphellaria as well as in different genera of the Physciaceae (e.g., Dirinaria, Physcia, and Pyxine) and the Parmeliaceae (e.g., Parmelia and Evernia). 3,4 A previous report on the secondary metabolites of Pyxine berteriana (Physciaceae) from Brazil indicated that it contained atranorin, lichexanthone, methyl pyxinate, and pyxinol, according to TLC analysis. 4 In the course of the search for new metabolites from the lichen P. berteriana (Fée) Imshaug we have isolated two new fernene triterpenoids, fern-9(11)-en-3,19-dione (1) and 3β-acetoxyfern-9(11)-en-19-one (2), together with the known 3β-acetoxyfern-9(11)-en-19β-ol (3) and lichexanthone (4), which is a chemical marker of a group of species in the genus Pyxine. 5,6 The structure elucidation of compounds 1 and 2 is described herein. (Table 1) In accordance with the COSY spectrum, the signal at δ H 2.76 (H-2β) showed cross-peaks with the signals at δ H 2.20 (H-1β), 2.23 (H-2α), and 1.64 (H-1α). On the basis of the HMBC and HSQC spectra, the signals at δ H 2.76 and 2.23 (δ C 35.1, H-2) showed crosspeaks with the signals at δ C 40.4 (C-1), 216.6 (C-3), and 37.6 (C-10), establishing that C-3 corresponded to the carbonyl group at δ C 216.6. Further correlations in the HMBC spectrum of the singlet at δ H 1.30 (δ C 24.2) with the signals at δ C 37.6 (C-10), 40.4 (C-1), 46.4 (C-5), and 148.9 (C-9) allowed us to assign this methyl resonance to C-25. The NOESY correlations between H-5/CH 3 -23 and CH 3 -25/CH 3 -24 in conjunction with HSQC data permitted assignment of the 1 H and 13 C resonances of CH 3 -23 (δ H 1.04, δ C 24.3) and CH 3 -24 (δ H 1.12, δ C 21.7). HMBC correlations of these methyl protons with the signal at δ C 216.6 confirmed the assignment of this carbonyl group to C-3. The broad doublet at δ H 2.09 (δ C 38.8) was assigned to H-8 on the basis of the cross-peaks with the si...

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A strain of the lichen mycobiont of Ramalina celastri, isolated from ascospores, was cultured axenically on two solid media containing high amounts of the carbon source: sucrose in MY10 and mannitol in BMRM. Usnic acid, the major cortical lichen metabolite, was produced by the colonies grown on MY10, with a very high yield (7.9%) in comparison with that in the lichen thallus. Mycelia grown on BMRM did not produce the lichen secondary metabolite and rendered triacylglycerides (8.5%) instead. Analysis by GC-MS of the fatty acid methyl esters revealed the presence of oleic, palmitic and stearic acids as the main triacylglyceride constituents. The present results highlight the impact of the culture conditions on the lichen mycobiont secondary metabolism and confirm that MY10 is a useful medium to obtain usnic acid from mycobionts in the laboratory.

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