Marine macroalgae are an extremely valuable source of bioactive molecules with unique properties and multiple potential applications in the cosmeceutical, pharmaceutical, and food industries. Adriatic Sea is an extremely harsh environment characterized by high salinity, seasonal oscillations in temperature and relatively shallow depth which indicates increased UV radiation. It can be assumed that such conditions have forced macroalgae to evolutionary develop molecules which could through activation of anti-stress mechanisms enable surviving in such a hostile environment. With such a hypothesis, Codium adhaerens was sampled from the Adriatic Sea, extracted with methanol:dichloromethane and further fractionated by solid phase extraction to obtain less polar fractions (F3, F4). Chemical composition was determined by UHPLC-ESI-HRMS and the antioxidant potential was comprehensively evaluated using colorimetric assays (Folin-Ciocalteu, ABTS, DPPH, FRAP) and in vivo experiments on zebrafish Danio rerio.
Zebrafish D. rerio embryos were employed for this research, as currently one of the most valuable laboratory model organisms for bioactivity determination of natural and synthetic molecules. The results obtained from in vivo experiments on zebrafish embryos demonstrated protective effects of tested C. adhaerens fractions against H2O2 induced mortality (23% and 27% declined mortality in 500 μg/mL of F3 and F4 fractions), along with the significant decrease of reactive oxygen species (ROS) generation. F3 and F4 in concentration of 500 μg/mL significantly decreased (p<0.001) ROS generation (60.5 and 51.9 % decreased in comparison to H2O2 treatment group). The results obtained by in vivo assay on zebrafish embryos correlate well with the ones obtained by colorimetric methods since both C. adhaerens fractions (F3 and F4) exerted similar antioxidant activity responses. This can be explained by the presence of bioactive molecules (UHPLC-ESI-HRMS analysis)
with already proven antioxidant potential (e.g., carotenoid - fucoxanthin, chlorophyll derivatives - pheophytin a and pheophorbide a). It should be mentioned that the antioxidant activity cannot be related to the particular compound, since various bioactive molecules could work in synergy. Such findings point out C. adhaerens as an inexhaustible source of natural antioxidants that could be used in research of oxidative stress-related diseases such as cancer, cardiovascular and neurodegenerative diseases. This study is published in Pharmaceuticals (doi: 10.3390/ph14090944).