Publications by authors named "Mikael Fabritius"

5 Publications

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A novel UHPLC-ESI-MS/MS method and automatic calculation software for regiospecific analysis of triacylglycerols in natural fats and oils.

Anal Chim Acta 2022 Jun 1;1210:339887. Epub 2022 May 1.

Food Chemistry and Food Development, Department of Life Technologies, FI-20500, University of Turku, Turku, Finland. Electronic address:

Regioisomeric analysis of triacylglycerols (TAGs) in natural oils and fats is a highly challenging task in analytical chemistry. Here we present a software (TAG Analyzer) for automatic calculation of regioisomeric composition of TAGs based on the mass spectral data from recently reported ultra-high performance liquid chromatography electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) method for analyzing TAG regioisomers. The software enables fast and accurate processing of complex product ion spectra containing structurally informative diacylglycerol [M+NH-RCOH-NH] and fatty acid ketene [RCO] fragment ions. Compared to manual processing, the developed software offers higher throughput with faster calculation as well as more accurate interpretation of chromatographically overlapping isobaric TAGs. The software determines results by constructing a synthetic spectrum to match the measured fragment ion spectrum, and by reporting the optimal concentrations of TAGs used to create the synthetic spectrum. This type of calculation is often extremely challenging for manual interpretation of the fragment ion spectra of isobaric TAGs with shared fragments, hence the need for automated data processing. The developed software was validated by analyzing a wide range of mixtures of regiopure TAG reference compounds of known composition and a commercial olive oil sample. Additionally, the method was also applied for regiospecific analysis of TAGs in human milk as an example of natural fats and oils with a highly complex TAG profile. The results indicate that the software is capable of resolving regioisomeric composition of natural TAGs even of the most complex composition. This novel calculation software combined with our existing UHPLC-ESI-MS/MS method form a highly efficient tool for regioisomeric analysis of TAGs in natural fats and oils.
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http://dx.doi.org/10.1016/j.aca.2022.339887DOI Listing
June 2022

Direct infusion and ultra-high-performance liquid chromatography/electrospray ionization tandem mass spectrometry analysis of phospholipid regioisomers.

Rapid Commun Mass Spectrom 2021 Sep;35(18):e9151

Food Chemistry and Food Development, Department of Biochemistry, University of Turku, Turku, Finland.

Rationale: Phospholipids are important components of cell membranes that are linked to several beneficial health effects such as increasing plasma HDL cholesterol levels, improving cognitive abilities and inhibiting growth of colon cancer. The role of phospholipid (PL) regioisomers in all these health effects is, however, largely not studied due to lack of analytical methods.

Methods: Electrospray ionization mass spectrometry in negative mode produces structurally informative fragment ions resulting from differential dissociation of fatty acids (FAs) from the sn-1 and sn-2 positions, primarily high-abundance [RCOO] ions. The fragment ion ratios obtained with different ratios of regiopure phospholipid reference compounds were used to construct calibration curves, which allow determination of regioisomeric ratios of an unknown sample. The method was developed using both direct infusion mass spectrometry (MS) and ultra-high-performance liquid chromatography and hydrophilic interaction liquid chromatography mass spectrometry (UHPLC-HILIC-MS).

Results: The produced calibration curves have high coefficients of determination (R  >0.98) and the fragment ion ratios in replicate analyses were very consistent. A test mixture containing 60/40% ratios of all available regioisomer pairs was analyzed to test and validate the functionality of the calibration curves. The results were accurate and reproducible. However, regioisomeric quantification of certain chromatographically overlapping compounds is restricted by the relatively wide window in precursor ion selection of the MS instrument used.

Conclusions: This method establishes a framework for analysis of phospholipid regioisomers. Specific regioisomers can be quantified using the existing data, and method development will continue with improving chromatographic separation and exploring the fragmentation patterns and efficiencies of different PL classes and FA combinations, ultimately to refine this method for routine analysis of natural fats and oils.
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http://dx.doi.org/10.1002/rcm.9151DOI Listing
September 2021

Strategy for stereospecific characterization of natural triacylglycerols using multidimensional chromatography and mass spectrometry.

J Chromatogr A 2021 Mar 12;1641:461992. Epub 2021 Feb 12.

Food Chemistry and Food Development, Department of Life Technologies, University of Turku, FI-20014 Turku, Finland.

Stereoisomeric determination of individual triacylglycerols (TAGs) in natural oils and fats is a challenge due to similar physicochemical properties of TAGs with different fatty acid combinations. In this study, we present a strategy to resolve the enantiomeric composition of nutritionally important TAGs in sea buckthorn (Hippophaë rhamnoides) as an example food matrix. The targeted strategy combines 1) fatty acid profiling with GC, 2) separation of TAGs with RP-HPLC, 3) stereospecific separation with chiral-phase HPLC and 4) structural characterization with MS. Three major asymmetric diacid- and triacid-TAG species were analyzed in sea buckthorn pulp oil. Off-line coupling of RP-HPLC and chiral-phase HPLC allowed separation of several TAG regioisomers and enantiomers, which could not be resolved using one-dimensional techniques. Enantiomeric ratios were determined and specific structural analysis of separated TAGs was performed using direct inlet ammonia negative ion chemical ionization method. Of the TAG 16:0/16:1/16:1 palmitic acid (C16:0) was located predominantly in a primary position and the enantiomeric ratio of TAG sn-16:1-16:1-16:0 to sn-16:0-16:1-16:1 was 70.5/29.5. Among the TAGs 16:0/16:0/18:2 and 16:0/16:0/16:1, only ca 5% had C16:0 in the sn-2 position, thus, ca 95% were symmetric sn-16:0-18:2-16:0 and sn-16:0-16:1-16:0. The enantiomeric ratio of triacid-TAGs containing C16:0 and two unsaturated fatty acids (palmitoleic C16:1, oleic C18:1 or linoleic acids C18:2) could not be resolved due to lack of commercial enantiopure reference compounds. However, it became clear that the targeted strategy presented offer unique and convenient method to study the enantiomeric structure of individual TAGs.
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http://dx.doi.org/10.1016/j.chroma.2021.461992DOI Listing
March 2021

Direct inlet negative ion chemical ionization tandem mass spectrometric analysis of triacylglycerol regioisomers in human milk and infant formulas.

Food Chem 2020 Oct 6;328:126991. Epub 2020 May 6.

Food Chemistry and Food Development, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland. Electronic address:

A previously developed direct inlet tandem mass spectrometric method for analysis of triacylglycerol (TAG) regioisomers was updated and validated for operation with current instrumentation with improved sensitivity and throughput. TAG regioisomers in pooled Chinese and Finnish human milk samples, two bovine milk samples and 11 infant formulas were identified and quantified. A total of 241 TAG regioisomers were identified and quantified, consisting of over 60 mol% of all TAGs in the human milk samples. The infant formulas deviated largely from human milk in regioisomeric composition of TAGs. In the Finnish and Chinese human milks, the most abundant ones were 1,3-dioleoyl-2-palmitoylglycerol (OPO; 7.4 and 8.8 mol% of all TAGs) and 1(3)-linoleoyl-2-palmitoyl-3(1)-oleoylglycerol (LPO; 4.7 and 8.3 mol% of all TAGs). In the infant formulas 1,2(2,3)-dioleoyl-3(1)-palmitoylglycerol (OOP) and 1(3)-linoleoyl-2-oleoyl-3(1)-palmitoylglycerol/1(3)-palmitoyl-2-linoleoyl-3(1)-oleoylglycerol (LOP/PLO) were more abundant than OPO and LPO. The differences between human milk and infant formula prompt for further development of current formulas.
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http://dx.doi.org/10.1016/j.foodchem.2020.126991DOI Listing
October 2020

Determination of vitamin K composition of fermented food.

Food Chem 2019 Mar 24;275:515-522. Epub 2018 Sep 24.

Food Chemistry and Food Development, Department of Biochemistry, FI-20014, University of Turku, Turku, Finland. Electronic address:

A rapid ultra-high performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometric (UHPLC-APCI-MS/MS) method was developed for the analysis of vitamin K compounds: phylloquinone (PK) and menaquinones (MK-n). Non-chlorinated mobile phase composition was optimized for separation of eight vitamin K compounds on a reversed phase column in 10 min. Sample treatment with liquid and solid phase extractions and by the use of MK-4 as an internal standard enabled the quantitation of microgram level of vitamin K compounds in food. The method was used to screen and quantitate vitamin K from 17 fermented food products. The highest amount of PK was detected in kimchi (42 µg/100 g), whereas the highest MK-7 content was detected in natto (902 µg/100 g). Some MK-9 was present in kefir (5 µg/100 g). Two Chinese fermented soybean pastes contained significant amount of MK-6 (5-36 µg/100 g), MK-7 (12-86 µg/100 g), and MK-8 (22-44 µg/100 g).
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http://dx.doi.org/10.1016/j.foodchem.2018.09.136DOI Listing
March 2019
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