A new approach for analysis of polyprenols by a combination of thin-film chemical deposition and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RATIONALE: The polyprenols are involved in some essential biosynthetic pathways and serve as ubiquitous components of cellular membranes, so their fingerprinting in natural samples is of great interest. Previous studies indicate that due to the high hydrophobicity of polyprenols their direct analysis by mass spectrometry with soft ionization techniques may be difficult and require preliminary off-line derivatization. Hence, a method for rapid and sensitive screening of polyprenols is required. METHODS: A combination of thin-film chemical deposition and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for analysis of the polyprenol profile of Abies sibirica L. extract. Polyprenol-based monolayers were formed at the interphase of aqueous barium acetate solution, supplemented with 2,5-dihydroxybenzoic acid, and an n-hexane solution of polyprenols directly on a MALDI target plate. RESULTS: Peaks corresponding to [M - H + Ba]+ ions were observed in the MALDI-TOF mass spectra of polyprenols. A total of nine polyprenol homologues were identified with a polyprenol of 16 isoprene units dominating. The limit of detection was established at the level of 6 pg. Possible mechanisms of formation of [M - H + Ba]+ ions of polyprenols were discussed. CONCLUSIONS: The proposed approach can be suitable for high-throughput screening of polyprenols in biological samples of different origin due to easy sample preparation and high sensitivity.

Thin Film Chemical Deposition Techniques as a Tool for Fingerprinting of Free Fatty Acids by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

Metabolic fingerprinting is a powerful analytical technique, giving access to high-throughput identification and relative quantification of multiple metabolites. Because of short analysis times, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is the preferred instrumental platform for fingerprinting, although its power in analysis of free fatty acids (FFAs) is limited. However, these metabolites are the biomarkers of human pathologies and indicators of food quality. Hence, a high-throughput method for their fingerprinting is required. Therefore, here we propose a MALDI-TOF-MS method for identification and relative quantification of FFAs in biological samples of different origins. Our approach relies on formation of monomolecular Langmuir films (LFs) at the interphase of aqueous barium acetate solution, supplemented with low amounts of 2,5-dihydroxybenzoic acid, and hexane extracts of biological samples. This resulted in detection limits of 10-13-10-14 mol and overall method linear dynamic range of at least 4 orders of magnitude with accuracy and precision within 2 and 17%, respectively. The method precision was verified with eight sample series of different taxonomies, which indicates a universal applicability of our approach. Thereby, 31 and 22 FFA signals were annotated by exact mass and identified by tandem MS, respectively. Among 20 FFAs identified in Fucus algae, 14 could be confirmed by gas chromatography-mass spectrometry.