Mass spectral fragmentations of cholesterol acetate oxidation products

Pelillo, Marco; Galletti, Guido C.; Lercker, Giovanni

doi:10.1002/1097-0231(20000730)14:14<1275::aid-rcm25>3.0.co;2-d

Cited by 15 publications

(10 citation statements)

References 15 publications

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“…1B) based on the published spectrum of an acetate derivative (32). Comparison of the M. brevicollis compound (1A; Table 1) with this spectrum reveals identical fragment masses and relative abundances, supporting the identification.…”

Section: Resultssupporting

confidence: 54%

“…The significant 111-Da fragment ion is often attributed to the loss of a side chain with a single unsaturation. The position of this double bond, however, is difficult to deduce from fragmentation patterns alone (32,37). The base peak of 1A is a m/z 362 fragment that commonly results from cleavage of the side chain favored by an unsaturation in the C-22 position.…”

Section: Resultsmentioning

confidence: 99%

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Sterols in a unicellular relative of the metazoans

Kodner

Summons

Pearson

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Molecular clocks suggest that animals originated well before they first appear as macroscopic fossils, but geologic tests of these hypotheses have been elusive. A rare steroid hydrocarbon, 24-isopropylcholestane, has been hypothesized to be a biomarker for sponges or their immediate ancestors because of its relatively high abundance in pre-Ediacaran to Early Cambrian sedimentary rocks and oils. Biolipid precursors of this sterane have been reported to be prominent in several demosponges. Whether 24-isopropylcholestane can be interpreted as a sponge (and, hence, animal) biomarker, and so provide clues about early metazoan history, depends on an understanding of the distribution of sterol biosynthesis among animals and their protistan relatives. Accordingly, we characterized the sterol profile of the choanoflagellate Monosiga brevicollis, a representative of the unicellular sister group of animals. M. brevicollis does not produce a candidate sterol precursor for 24-isopropylcholestane under our experimental growth conditions. It does, however, produce a number of other sterols, and comparative genomics confirms its biosynthetic potential to produce the full suite of compounds recovered. Consistent with the phylogenetic position of choanoflagellates, the sterol profile and biosynthetic pathway of M. brevicollis display characteristics of both fungal and poriferan sterol biosynthesis. This is an example in which genomic and biochemical information have been used together to investigate the taxonomic specificity of a fossil biomarker.choanoflagellates ͉ molecular fossils ͉ origin of metazoans ͉ Monosiga brevicollis S terols constitute a diverse class of triterpenoid lipids having wide ranging importance in biology. All eukaryotes require sterols; they serve important functions because membrane lipids play roles as developmental regulators and precursors to steroid hormones in multicellular organisms. Recently, sterols have emerged as an important investigative tool for paleontologists (1-4) because steranes, the hydrocarbon skeletons of sterols, resist microbial attack and remain stable over long periods of time. Thus, they are well represented as molecular fossils in sedimentary rocks. The discovery of diverse steranes in the geologic record has fueled a search for unique precursor sterols in many branches of the eukaryotic tree, because for a molecular fossil to be useful as a biomarker, it must have significant taxonomic and/or physiological specificity.One candidate for a paleobiologically useful biomarker is 24-isopropylcholestane, the geologically stable derivative of the C 30 sterol 24-isopropylcholesterol. Although much of eukaryotic sterol diversity is manifested in double bonds and functional groups that do not preserve in fossil hydrocarbon skeletons, the isopropyl moiety in the side chain of 24-isopropylcholesterol and related sterols results in a structure that is both unique and preservable. Particularly abundant as a molecular fossil in rocks deposited during the Ediacaran and Cambrian periods (3, 5) i...

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Sterols in a unicellular relative of the metazoans

Kodner

Summons

Pearson

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The fragmentation of sterols is very complicated because of their polycyclic structure. Thus, the identification of direct fragments is difficult because of the specific mechanisms of fragmentation (i.e., retro-Diels-Alder reaction, neutral molecule elimination) (17).…”

Section: Discussionmentioning

confidence: 99%

Rapid quantification of free and esterified phytosterols in human serum using APPI-LC-MS/MS

Lembcke

Ceglarek

Fiedler

et al. 2005

Journal of Lipid Research

138

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A novel analytical platform based on liquid chromatography and tandem mass spectrometry using atmospheric pressure photoionization was applied for the simultaneous quantification of free and esterified ␤ -sitosterol, campesterol, brassicasterol, and stigmasterol. The total time for sample pretreatment and analysis could be reduced from ‫ف‬ 3 h [gas chromatography-mass spectrometry (GC-MS)] to 15 min. The detection limits of the different phytosterols ranged between 0.25 and 0.68 g/l. Linear ranges were between 1 and 1,000 g/l. The within-run and between-run variabilities ranged between 1.4% and 9.9%. The analytical sensitivity was at least 150-fold higher compared with GC-MS. Our new method allows a rapid and simultaneous determination of free and esterified phytosterols in serum. Phytosterols are common components of plant foods, especially vegetable oils, seeds, nuts, and cereals (1). They are structurally similar to cholesterol, differing only in the number of carbons or double bonds in the side chain. An average Western diet contains ‫ف‬ 200-400 mg of phytosterols per day (e.g., ␤ -sitosterol, campesterol, stigmasterol, and brassicasterol). All serum and tissue phytosterols are derived exclusively by intestinal absorption. Therefore, serum levels of phytosterols reflect dietary plant sterol intake and intestinal absorption (2). The individual differences in plasma phytosterol concentrations are highly heritable (3). Compared with dietary cholesterol, the intestinal absorption rate of dietary phytosterols is markedly lower, because the bulk of absorbed phytosterols is immediately secreted into the intestine by the ATP-binding cassette half-transporters ABCG5 and ABCG8 of the enterocytes (4). Mutations in either of the transporter genes have been identified as the cause of sitosterolemia, a rare autosomal recessive lipid disorder that is characterized by markedly increased serum phytosterol concentrations (e.g., ␤ -sitosterol Ͼ 50 mg/l) as a consequence of hyperabsorption and impaired biliary secretion of neutral sterols (5-7). These patients develop premature coronary heart disease (8, 9). A recent study in patients admitted for elective coronary artery bypass graft surgery supports the hypothesis that even slightly increased campesterol (3.8 Ϯ 1.6 mg/l) and ␤ -sitosterol (3.1 Ϯ 1.1 mg/l) concentrations in serum may contribute to the risk of coronary heart disease (10).Sensitive analytical methods are necessary to detect physiological phytosterol concentrations and even slightly increased concentrations in human serum. Currently available methods for the measurement of phytosterols in serum are based on GC-MS. However, this analytical platform is time-consuming and requires a laborious pretreatment procedure (hydrolysis, liquid-liquid extraction, and derivatization) and a large sample volume (11,12). Recently described liquid chromatography-mass spectrometry (LC-MS) methods for the determination of cholesterol and oxidized metabolites in human plasma also include time-consuming extraction and hydroly...

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“…Δ 5 ‐Unsaturation can also produce a typical retro‐Diels‐Alder (rDA) reaction on ring B, with the loss of rings A and B and the formation of the fragment [M–211] + (VII), i.e., [MTMSOHC 9 H 13 ] + ; this kind of fragmentation is also abundant in acetate derivatives of sterols 30. Another common fragment is considered to be derived from the loss of the side chain and the D ring (VI), and appears at m/z 213 for sterols carrying one unsaturation in their ring structure; this fragmentation pathway is not typical of solely Δ 5 ‐sterols, but can provide important information on the number of unsaturations and other functional groups on the A and B rings, especially for oxidised sterols 31…”

Section: Resultsmentioning

confidence: 99%

Book Review: The Biological Chemistry of the Elements The inorganic chemistry of life by J. J. R. Fraústo da Silva and R. J. P. Williams

Kersting

2002

ChemBioChem

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Mass spectral fragmentations of cholesterol acetate oxidation products

Cited by 15 publications

References 15 publications

Sterols in a unicellular relative of the metazoans

Sterols in a unicellular relative of the metazoans

Rapid quantification of free and esterified phytosterols in human serum using APPI-LC-MS/MS

Book Review: The Biological Chemistry of the Elements The inorganic chemistry of life by J. J. R. Fraústo da Silva and R. J. P. Williams

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