Chemistry of the lichen Psoroma xanthomelanum Nyl.

PASSO, A., CALVELO, S. & STOCKER, E.

Tartu Estonia

Congreso; V IAL (International Association for Lichenology) Symposium; 2004

University of Tartu, Estonia

Until recently, the knowledge of the chemistry of the genus Psoroma (Pannariaceae, lichenized ascomicota) was only poor.             Psoroma st.lat. is know to produce no substances of taxonomical relevance and for the remaining species of Psoroma only a few compounds have been described in the past, although they were not included in the taxonomical studies of this genus.             The “foliose” group of the genus (now regarded as Pannaria) is probably the best known. This group is characterized by the presence of depsidones like pannarin, vincanicin and leprolomin. But the chemistry profile is not very complex, containing only one or two major substances.             Psoroma xanthomelanum Nyl, an endemic species of New Zealand, is related to this group regarding its morphology and anatomy.             The present study aimed to get more detailed information about its secondary compounds. Collections of Psoroma xanthomelanum from different herbaria (S, BM, BCRU, MSC) were analuzed by TLC and HPLC. Two major compounds were found by HPLC, pannarin and contortin. By additional TLC, the presence of the two major substances was confirmed, as a further metabolite the terpenoid zeorin was present and traces of porphyrilic acid were detected.             The chemistry of P. xanthomelanum is consistent with the typical compounds found in Psoroma s.lat., and seems to confirm the close relationship among these species. But, as was shown in this study, the chemical profile is more complex that usual. The presence of the terpenoid zeorin may consitute a diagnostic character of P. xanthomelanum.