The main secondary metabolites of lichens are unique aromatic and aliphatic compounds, i.e., lichen compounds. Most known lichen compounds are products of the acetate–malonate biosynthetic pathway. Lichen compounds are known to possess broad spectra of biological activity such as antioxidant, antibacterial, and cytotoxic [1, 2].

The goal of the research was to determine by HPLC the contents of phenolic metabolites in Cladonia lichens growing under the contrasting climatic conditions of Yakutia and Belarus.

The study included 52 herbarium specimens belonging to 15 species of Cladonia lichens collected in Yakutia and preserved in the herbarium of the Institute of Biological Problems of the Cryolithozone, SB, RAS (SASY) and in Belarus and preserved in the herbarium of V. F. Kuprevich Institute of Experimental Botany, NASB (MSK). Herbarium specimens of lichens were designated for storage in 1956–2016. According to prior investigations, the storage time of lichens under herbarium conditions had no effect on the contents of secondary metabolites in them [3].

Secondary metabolites were isolated, identified, and analyzed as before [4]. The studied lichens contained eight main phenolic metabolites from the lichen compound group including five that were depsides (atranorin and perlatolic, barbatic, squamatic, and thamnolic acids); one, a depsidone (fumarprotocetraric acid); and two, dibenzofurans (usnic and isousnic acids).

The constituent compositions of most studied lichens agreed with those in the literature [5]. Lichens C. arbuscula, C. cariosa, C. mitis, and C. stellaris collected in Yakutia and Belarus were shown to have component compositions belonging to the same known chemotypes that are broadly distributed in northern populations of these species.

However, lichens C. coniocraea and C. uncialis represented new and previously unknown chemotypes (Table 1). C. uncialis contained thamnolic (2) and not squamatic acid (3) only in samples from Belarus. However, the C. coniocraea chemotype containing the main component barbatic (4) and not fumarprotocetraric acid (1) was characteristic of both study sites.

Table 1. Lichen Compound Contents in Thalli Collected in Yakutia and Belarus, % of Dry Mass
Full size table

The quantitative contents of individual lichen compounds varied over wide ranges. For example, the content of 2 varied from trace quantities in C. cenotea to 11.8% of the dry mass in C. digitata (Table 1). Usnic acid (5 in six of fifteen studied species) and fumarprotocetraric acid (1 in eight of fifteen studied species) were most often encountered of aromatic compounds in the studied Cladonia species. The highest content of usnic acid (up to 5.3% of the dry mass) was observed in C. deformis; of fumarprotocetraric acid (up to 3.8% of the dry mass), in C. coniocraea (chemotype I).

Thus, new and previously unknown chemotypes were found in the lichens C. coniocraea and C. uncialis. The constituent compositions and quantitative contents of aromatic lichen compounds could be used to formulate compositions for biopreparations and food additives.