Final report (Febuary 2016)

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As proposed, the protection mechanisms of extremophilic algae against UV-stress were investigated, considering analytical, chemosystematic and pharmacological aspects. Initially, our interest was targeted towards alpine species, which were selected and cultivated in-house. This showed to be problematic, because even if optimum conditions were applied, the obtained biomass was low, sufficient for a first analytical or pharmacological screening, but most of the time not for isolation purposes. Regarding the compounds of interest, our main focus was targeted towards mycosporine amino acids (MAAs), known photoprotectants in algae. Thus, we utilized marine algae for their isolation. They were either commercially available (Prophyra sp. or Palmaria palmata) or material supplied by Prof. Ulf Karsten, University of Rostock, Germany.

Using the aforementioned material, Ms. Hartmann was able to develop a generally applicable isolation protocol for MAAs, which combined several chromatographic techniques (ion-exchange, SPE using activated carbon, and semi-preparative HPLC). This procedure resulted in pure and unambiguously identified compounds (by NMR and MS), a fact that is of great importance. Because of their extremely high extinction coefficients MAAs might falsely be considered pure (if only monitored by UV-vis), an aspect that was overlooked in many previous studies. With well-characterized compounds at hand, two new analytical approaches were developed: the separation and quantitative determination of MAAs by Hydrophilic Interaction Chromatography (HILIC) and by Capillary Electrophoresis (CE). Furthermore, these refined techniques resulted in the isolation of two novel MAAs, prasiolin from Prasiola calophylla and catenelline from Catenella repens. Their quantification allowed first insights into their distribution in algae and is of great chemosystematic relevance. In accordance to our proposal also pharmacological aspects of MAAs were studied. In course of a four month stay at the University of Athens, Greece, Ms. Hartmann could develop and validate a collagenase assay for high-throughput screening, and show, for the first time, that some MAAs possess collagenase inhibitory potential. This confirms, in addition to their ability to absorb UV-A and UV-B, their potential suitability as anti-aging sunscreens.

Together with Dr. Andreas Albert from the Helmholtz center in Munich, Germany, irradiation experiments were performed in a sun-simulator. For this purpose some of the originally selected alpine algae were exposed to defined amounts of UV-A and UV-B, in order to study possible changes in the metabolite patterns. Interestingly, besides effects on carotenoid levels mainly the production of highly polar substances increased. Even tedious and tricky, due to the minute amount of available samples, it was possible to isolate and identify respective compounds. They showed to be aromatic amino acids, nucleic bases and nucleotides. Their increased production in algae as a consequence of UV-stress has never been reported before. To study these effects in detail a suitable HPLC method was developed, and several green algae and cyanobacteria analyzed for the content of respective primary metabolites, after they were exposed to different dosages of UV-A and UV-B light.

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Our efforts resulted in several posters presented at national (Graz, Innsbruck) and international conferences (Guimaraes, Budapest), as well as publications in international, peer-reviewed journals (4 accepted, 2 in preparation). They are:

  • Effects of elevated ultraviolet radiation on primary metabolites in selected alpine algae and cyanobacteria, A. Hartmann, A. Albert, M. Ganzera, Journal of Photochemistry and Photobiology B, 149, 149-155, 2015. (open access)
  • Inhibition of collagenase by mycosporine-like amino acids from marine sources, A. Hartmann, J. Gostner, J. E. Fuchs, E. Chaita, N. Aligiannis, L. Skaltsounis, M. Ganzera, Planta Medica, 81, 813-820, 2015.
  • Analysis of mycosporine-like amino acids by hydrophilic interaction liquid chromatography and a novel MAA from the red alga Catenella repens, A. Hartmann, K. Becker, U. Karsten, D. Remias, M. Ganzera, Marine Drugs, 13, 6291-6305, 2015. (open access)
  • Prasiolin, a new UV-sunscreen compound in the terrestrial green macroalga Prasiola calophylla (Carmichael ex Greville) Kützing (Trebouxiophyceae, Chlorophyta), A. Hartmann, A. Holzinger, M. Ganzera, U. Karsten, Planta, 243, 161-169, 2016. (open access)
  • Separation of mycosporine-like amino acids by capillary electrophoresis, A. Hartmann, A. Murauer, M. Ganzera, in preparation.
  • Immunomodulatory effects of the mycosporine-like amino acids shinorine and porphyra-334, K. Becker, A. Hartmann, M. Ganzera, D. Fuchs, J. Gostner, in preparation.
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