Abstract
New resources of food, pharmaceuticals or biotechnological products are needed. The huge biodiversity of aero-terrestrial lichen-symbiont microalgae belonging to the Chlorophyta group remains unexplored despite they present interesting features such as extreme stress tolerance and growth in water shortage. Appropriateness for human consumption demands the demonstration of the absence of toxic effects. In vitro biocompatibility of crude homogenates of axenic microalga Asterochloris erici, isolated from the lichen Cladonia cristatella, was analyzed after treatment of cultured L929 fibroblasts with different concentrations of microalgal homogenates. The microalgal protein content (37%) was similar to spirulina or soybean. Antioxidant capacity (10.6 ± 0.6 µmol TE/g WW) or phenolic content (7.5 ± 0.5 mg GAE/g DW) were high compared to Chlorella. The results show that crude homogenates of A. erici do not induce cytotoxicity but seem to have some cytostatic effect inducing slight cell cycle alterations and intracellular reactive oxygen species (ROS) increase at the highest concentration. Carotenoid analysis demonstrates high contents of lutein (1211 µg/g microalga DW), a xanthophyll with antioxidant and cytostatic properties in vivo and high commercial added value. These findings confirm that Asterochloris erici can be suitable for the development of alimentary or pharmaceutical applications and further in vivo animal testing. The cytostatic effects should be further investigated for antitumor agents.
Highlights
Lichen thalli are the outcome of close and cyclical symbiotic associations involving, at least, two different organisms, a heterotrophic fungus and photoautotrophic partners [1,2], such photobionts being unicellular green algae or/and cyanobacteria
Microalgal biotechnology has been developed for various commercial applications; as photosynthetic organisms, algae contain pigments such as chlorophylls together with high contents of antioxidants, proteins, vitamins and polysaccharides, which can be applied for nutrient supplements, cosmetic purposes or human or animal consumption [9,10,11,12,13]
The ash content was 5 ± 1% DW and was a value of the same order of magnitude as those reported for the green microalgae chlorella
Summary
Lichen thalli are the outcome (holobiont) of close and cyclical symbiotic associations involving, at least, two different organisms, a heterotrophic fungus (mycobiont) and photoautotrophic partners (photobionts) [1,2], such photobionts being unicellular green algae (phycobionts, chlorobionts) or/and cyanobacteria (cyanobionts). Lichenization allows the symbionts to colonize diverse terrestrial habitats from the seashores to the high mountains, reaching a large distribution from the tropics to the polar regions [3,4]. Their long life and adaptation to extreme environmental conditions are supported by the production of numerous protective virtually unexplored compounds against different physical and biological stresses [5]. Chlorophyta, are a huge and diverse phylum of eukaryotic microorganisms These eukaryotic photoautotrophs should not be confused with the prokaryotic cyanobacteria, known as blue-green algae. Microalgal biotechnology has been developed for various commercial applications; as photosynthetic organisms, algae contain pigments such as chlorophylls together with high contents of antioxidants, proteins, vitamins and polysaccharides, which can be applied for nutrient supplements, cosmetic purposes or human or animal consumption [9,10,11,12,13]
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