First, the water-column and sediment porewater RDOM samples were collected and extracted. In order to reduce the molecular complexity, the samples were fractionated by polarity by using different solvents.
Non-fractionated DOM pools and fractions were analyzed for bioactive potential. The first results showed antioxidant activities and phenolic content much higher of what is commonly found in macroalgae and microalgae with cosmeceutical purposes, in vegetables, in fruits, in honey, and in the same magnitude as propolis. A surprising finding was the excellent solar protection factor index (SPF), especially of the sediment-derived DOM, which showed SPF/UVASPF ratios very closed to the ideal sunscreen.
Regarding the immunoactivity, the pro-inflammatory cytokine TNF-α was the most expressed. The pro-inflammatory IL-2, GM-CSF and IFN-γ, and the anti-inflammatory IL-4 were only expressed in some of the fractions, whereas IL-13, IL-10, IL-5 and IL-12 (p70) were not expressed.
For all these tests, the sediment porewater DOM was the most biologically active, presumably related to its elevated sulfur content. In some cases, a magnification of the bioactive potential of DOM was observed after fractionating the crude material, indicating a molecular-dependent bioactive response.
Thanks to an EMBRIC transnational access program (
http://www.embric.eu(s’ouvre dans une nouvelle fenêtre)) Dr. Catalá measured the anti-tumoral and anti-microbial activity of RDOM. The anti-tumoral activity with human prostate cancer cells (PC3), with its healthy counterpart for comparison, was measured. Whereas some samples did not show a cytotoxic effect on both human cells, some other showed antiproliferative effect on normal cells or/and tumor cells. The anti-microbial testing was evaluated with seven different multidrug-resistant strains from the Collection of Institut Pasteur. Slight anti-microbial activities were found in the strains Staphylococcus aureus aureus and Klebsiella pneumoniae pneumoniae.
Since no clear patterns were observed in any of the two assays, there is a need for other types of pharmaceutical tests adapted to complex natural mixtures.
Together with the bioactivity tests, the samples molecular composition was elucidated. The results showed how the porewater samples are molecularly different regarding the water column samples. Most of the formulas present in the porewater are exclusive and they are not present in the other two groups. In addition, the fractionation by polarity was very successful in separating the RDOM in different molecular groups.
Due to initial complications, the publication of scientific papers was not achieved yet. Instead, a first publication linking antioxidant activity and phenolic content with the molecular features is in preparation, together with a second publication on the immunoactivity.
Throughout the project, Dr. Catalá has given lectures to a variety of audiences. In the host and all collaborating institutions, she has given lectures presenting her project. She has presented her work at the 2018 Ocean Sciences Meeting conference (Portland, February 2018). In January 2019, she gave a lecture at the microbiology seminar at the Institut Pasteur (Paris) and she presented her results in the final EMBRIC meeting in early 2019. Two press releases have been published at Oldenburg University, one explaining what her research consisted of (
https://uol.de/news-detail/die-schatztruhe-des-ozeans-oeffnen-2153/(s’ouvre dans une nouvelle fenêtre)) and the other concluding the results obtained and future perspectives (
https://www.presse.uni-oldenburg.de/mit/2019/211.html(s’ouvre dans une nouvelle fenêtre)).
