Abstract
In the present study, the chemical composition of the microalga Euglena cantabrica was investigated. The extraction of bioactive compounds was done using pressurized liquid extraction (PLE) at different temperatures (40–180 °C) and using green solvents (ethanol-water mixtures). A statistical design of experiments was used to optimize the maximum antioxidant capacity of the extracts by response surface methodology. The antioxidant capacity was determined through the inhibition of 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, while the chemical analyses of the extracts were carried out using different chromatographic techniques. Chlorophylls and carotenoids were analyzed by high-performance liquid chromatography coupled to a diode array detector and mass spectrometry (HPLC-DAD-MS/MS) and carbohydrates by gas chromatography with flame ionization detection (GC-FID) and high-pressure size-exclusion chromatography coupled to an evaporative light-scattering detector (HPSEC-ELSD). The results showed different possibilities for the extraction conditions, depending on the desired bioactivity or chemical composition. Briefly, (i) mixtures of ethanol-water containing around 40% ethanol at 180 °C gave the best antioxidant capacity, (ii) mixtures containing around 50% ethanol at 110 °C gave the best yield of β-glucan paramylon, and (iii) the use of pure ethanol at a low temperature (40 °C) is the best choice for the recovery of carotenoids such as diatoxanthin. Summing up, E. cantabrica seems to be a good candidate to be used in biorefinery to obtain different bioactive compounds.
Highlights
In spite of the fact that macroalgae have been used in China since 1000 b.c. and for ethnical uses in the Mayan culture and certain African tribes, they have not been used in a massive way until the middle of the 20th century
Extracts with high antioxidant capacities can be obtained at 180 ◦ C with 41.1% EtOH, according to the response surface obtained from the statistical analysis of the Design of Experiments (DoE)
The presence of natural pigments such as pheophytins and the carotenoid diatoxanthin in extracts obtained with pure ethanol has been confirmed by using HPLC-DAD-MS/MS
Summary
In spite of the fact that macroalgae have been used in China since 1000 b.c. and for ethnical uses in the Mayan culture and certain African tribes, they have not been used in a massive way until the middle of the 20th century. The way to cultivate them was investigated and simplified at. Mar. Drugs 2020, 18, 308; doi:10.3390/md18060308 www.mdpi.com/journal/marinedrugs Mar. Mar. Drugs 2020, 18, 308 x FOR PEER REVIEW M. 25 μm middle of the 20th century. The way to cultivate them was investigated and simplified at the the beginning of the century
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