Analysis on in vitro antioxidant capacities and phenolic composition of lichens extracts of Cetrarioid clade based on multivariate statistical analysis

Lichens are symbiotic organisms, which are composed by a mycobiont (fungus) and a photobiont (unicellular algae or cyanobacteria). They are widely distributed from the poles to equatorial zones. It is estimated that there are more than 28,000 species of lichens worldwide, with the Parmeliaceae family being the largest one. Within this, Cetrarioid clade stands out phylogenetically in number. The lichens of this clade have shown an interesting antioxidant activity. The aim of this study was to evaluate the antioxidant properties of 14 samples of lichen extracts from Cetrarioid clade and to classify lichen species by multivariate analysis. Principal component analysis (PCA) and hierarchical cluster (HCA) were performed using antioxidant properties (FRAP, ORAC and DPPH tests) and phenolic content as variables. The results showed that the antioxidant profiles were different between Dactylina arctica (Richardson) Nyl species and the rest of the studied species of the Cetrarioid clade, finding similarities between Nephromopsis stracheyi (C. Bab.) Mull. Arg., Tuckermannopsis americana (Spreng.) Hale and Vulpicida pinastri (Scop.) J.E. Mattsson and M. J. Lai. The HCA results demonstrated that lichen samples were clustered into three groups. Dactylina arctica was included in cluster 1 with high antioxidant activity and high phenolic content. Cluster 2 contained Nephromopsis stracheyi, Tuckermannopsis americana and Vulpicida pinastri with a medium content of phenols and moderate antioxidant activity. Finally, the rest of the lichen species, including those of the genus Cetraria, formed Cluster 3.