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Lichen specific metabolites (LSMs) have interesting biological activities and quantitative variations may be present intraspecifically. For example, variations in medullary fumarprotocetraric acid (FA) and cortical usnic acid (UA) were observed in the lichen Cladonia foliacea, but the mechanism of variation is not well understood. The current study aimed to characterise the quantitative variation of FA and UA and to investigate the association between lichen metabolite content and ecological / biological variables. Fungal and algal trees were constructed using fungal (nrITS, RPB2) and algal (nrITS) loci, respectively. Using a chiral chromatographic method, the contents of (-)-UA were determined in 29 C. foliacea specimens and range from 6.88 to 34.27 mg/g dry wt. The FA contents were lower and varied from 1.44 to 9.87 mg/g dry wt. Although the fungal tree showed two well resolved clades, no significant differences of UA or FA contents were found between the two fungal clades. However, a significantly higher UA/FA ratio as well as a unique habitat were found to be associated with specimens which contained the alga Asterochloris lobophora than those specimens associated other Asterochloris algae. Taking all predictive variables into account (i.e. substrate type, elevation, collection season, photobiont identity), the multivariate data analysis indicated that photobiont identity explained most of the variance of LSM contents in C. foliacea. Thus future LSM biosynthetic studies should take the photobiont into consideration when dealing with intraspecific quantitative variation. [ABSTRACT FROM AUTHOR]

Usnic acid (UA) is a chiral lichen metabolite with an interesting pharmacological profile. The aim of this study was to compare the anti-melanoma effect of (+)-UA and (−)-UA in an in vitro model by studying their impact on the cells as well as the processes associated with cancer progression. The effect of UA enantiomers on the viability, proliferation, and invasive potential of three melanoma cell lines (HTB140, A375, WM793) was evaluated. Their interaction with a chemotherapeutic drug—doxorubicin was assessed by isobolographic analysis. Anti-inflammatory and anti-tyrosinase properties of (+)-UA and (−)-UA were also examined. Both UA enantiomers dose- and time-dependently decreased the viability of all three melanoma cell lines. Their synergistic effect with doxorubicin was observed on A375 cells. (+)-Usnic acid at a sub-cytotoxic dose strongly inhibited melanoma cells migration. Both UA enantiomers decreased the release of pro-inflammatory mediators. The cytotoxic effect of (+)-UA and (−)-UA depends greatly on the melanoma cell type; however, the overall anti-melanoma potential is perspective. Our results indicate that the strategy of combining usnic acid enantiomers with cytostatic drugs may be an interesting option to consider in combating melanoma; however, further studies are required.

Usnic acid (UA) is a chiral lichen metabolite with an interesting pharmacological profile. The aim of this study was to compare the anti-melanoma effect of (+)-UA and (−)-UA in an in vitro model by studying their impact on the cells as well as the processes associated with cancer progression. The effect of UA enantiomers on the viability, proliferation, and invasive potential of three melanoma cell lines (HTB140, A375, WM793) was evaluated. Their interaction with a chemotherapeutic drug—doxorubicin was assessed by isobolographic analysis. Anti-inflammatory and anti-tyrosinase properties of (+)-UA and (−)-UA were also examined. Both UA enantiomers dose- and time-dependently decreased the viability of all three melanoma cell lines. Their synergistic effect with doxorubicin was observed on A375 cells. (+)-Usnic acid at a sub-cytotoxic dose strongly inhibited melanoma cells migration. Both UA enantiomers decreased the release of pro-inflammatory mediators. The cytotoxic effect of (+)-UA and (−)-UA depends greatly on the melanoma cell type; however, the overall anti-melanoma potential is perspective. Our results indicate that the strategy of combining usnic acid enantiomers with cytostatic drugs may be an interesting option to consider in combating melanoma; however, further studies are required. [ABSTRACT FROM AUTHOR]