Natural carotenoids from microalgae have raised a huge interest for their potential health benefits. Among microalgae species with high carotenoid content, Dunaliella salina has been highlighted since it is able to accumulate relatively high amounts of β-carotene and other carotenoids of industrial interest when grown under specific conditions. In the present contribution, extractions based on carbon dioxide under sub-and supercritical conditions have been optimized to improve the recovery of carotenoids and extracts purity from D. salina. An experimental design was employed to investigate the effect of pressure and temperature variations ranging from 250 to 400 bar and from 15 to 45 °C, respectively. The chemical characterization of the carotenoids extracts was carried out by HPLC-DAD. Moreover, inhibition of the acetylcholinesterase activity of all the extracts was measured by using a recently developed in-vitro fluorescence methodology. High carotenoid yield and purity were obtained at 302-313 bar and 45 °C. Nine carotenoids were identified and three other compounds were recognized as carotenoids and quantified. Acetylcholinesterase activity inhibition could be satisfactorily explained by a partial least-square model (63% explained variance in cross-validation) built considering the chemical composition of the different extracts. The model indicates a positive effect of lutein, 15-cis-β-carotene and the negative effect of zeaxanthin, cryptoxanthin and the ratio 9-cis-β-carotene/all-trans-β-carotene and 9-cis-β-carotene/total carotenoids in the inhibition of acetylcholinesterase enzyme.
Despite mass spectrometry
(MS) being proven powerful
for the characterization
of synthetic polymers, its potential for the analysis of single particle
microplastics (MPs) is yet to be fully disclosed. To date, MPs are
regarded as ubiquitous contaminants, but the limited availability
of techniques that enable full characterizations of MPs results in
a lack of systematic data regarding their occurrence. In this study,
an atmospheric solid analysis probe (ASAP) coupled to a compact quadrupole
MS is proposed for the chemical analysis of single particle microplastics,
while maintaining full compatibility with complementary staining and
image analysis approaches. A two-stage ASAP probe temperature program
was optimized for the removal of additives and surface contaminants
followed by the actual polymer characterization. The method showed
specific mass spectra for a wide range of single particle MPs, including
polyolefins, polyaromatics, polyacrylates, (bio)polyesters, polyamides,
polycarbonates, and polyacrylonitriles. The single particle size detection
limits for polystyrene MPs were found to be 30 and 5 μm in full
scan and selected ion recording mode, respectively. Moreover, results
are presented of a multimodal microplastic analysis approach in which
filtered particles are first characterized by staining and fluorescence
microscopy, followed by simple probe picking of individual particles
for subsequent analysis by ASAP-MS. The method provides a full characterization
of MP contamination, including particle number, particle size, particle
shape, and chemical identity. The applicability of the developed multimodal
method was successfully demonstrated by the analysis of MPs in bioplastic
bottled water.
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