Bioactive lichen metabolites: alpine habitats as an untapped source

Abstract

International audienceLichens are fungal and algal/cyanobacterial symbioses resulting in the production of specific metabolites. Some of these are forming an available biomass for phytochemical investigations, including the assessment of biological activities of the isolated compounds. The alpine or polar region are characterised by highly stressful environmental conditions for many organisms, but lichens are among the dominating organisms in these habitats. In the performant mutual protective system, lichen fungi often accumulate high amounts of metabolites with specific physicochemical properties (UV absorbents, hydrophobicity) which help the lichens to survive. Unique secondary metabolites and polysaccharides have been isolated and tested from these organisms. Even though this has been tested until now only with a low number of compounds so far, interesting activities have been recorded. We review here some of the antimicrobial, anti-inflammatory, antiproliferative and antioxidant activities properties described. Solutions with axenic biotechnological cultivation of each symbiotic partner and particularly the mycobiont to obtain the lichen secondary metabolites are challenging to overcome the limitations for the supply of these rare compounds. Additionally, these lichens appear to harbour a diversity of culturable microorganisms from which active compounds have also been isolated recently

In vitroevaluation of the antibacterial activity of extracts from 34 species of North American lichens

“…Lichens represent one of the more promising potential reservoirs for low molecular weight secondary compounds with more than 1000 different secondary chemicals reported for lichens and their cultured mycobionts (Molnar & Farkas, 2010). Various lichen-derived compounds have been shown to have antimicrobial activities (Boustie et al, 2011;Podterob, 2008;Shrestha & St. Clair, 2013a;Shukla et al, 2010). Activity of lichen compounds has also been demonstrated against a limited number of drug-resistant pathogenic microbes including vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus (Elo et al, 2007;Kokubun et al, 2007;Lauterwein et al, 1995).…”

The adaptive radiation of lichen-forming Teloschistaceae is associated with sunscreening pigments and a bark-to-rock substrate shift

“…These secondary metabolites are produced by the fungal partner, and their crystals alter the spectral composition of the light that goes through the cortex (20) by absorbing visible blue light, UV-B and -A radiations (21,22). Synthesis of anthraquinones and other lichen pigments is stimulated by UV-B radiation (e.g., refs.…”

Fungal Metabolites for the Control of Biofilm Infections

“…Many of these studies were directed against specific pathogenic biofilms, e.g., Lentinula edodes extract against the bacterial human pathogens Actinomyces naeslundii, Prevotella intermedia, Neisseria subflava, and Streptococcus sanguinis [34,35], sometimes using highly elaborated and specific methods [36]. Also lichens, the association between fungi and algae, have been investigated over decades for their spectrum of bioactive secondary metabolites; however, only relatively few reports appeared on biofilm-modulating compounds from this group of organisms [37].…”