Authentic Standard Compounds Research Articles

Speciation of alkylated dibenzothiophenes through correlation of structure and gas chromatographic retention indexes

The gas chromatographic (GC) speciation of polycyclic aromatic sulfur heterocycles (PASH) in deeply desulfurized fuels is difficult without recourse to authentic standard compounds. Here we investigate the GC retention indexes for 30 alkylated dibenzothiophenes on two methylphenylsiloxane stationary phases of different selectivity (5% and 50% phenyl groups) with a view to avoid the synthesis of all congeners. The influence of the substitution pattern on the retention indexes is discussed. With the measured data it is possible to carry out a multiple linear regression (MLR) to calculate parameters for predicting the retention indexes of unknown polymethylated isomers based only on their structural features. Nine trimethyldibenzothiophene in a synthesis product are identified through their retention indexes. The retention indexes for a total of 43 alkyldibenzothiophenes are listed.

Concentrations of Anti‐Oxidant Compounds in Different Fruits

The levels of some anti-oxidant and anti-carcinogenic compounds were measured in six types of organically grown fruit (cranberries, blueberries, strawberries, blackberries, Concord grapes and guava). The fruit was ground to a fine powder in liquid nitrogen, and extracted with water, boiling water, or methanol. The extracts were analyzed by reverse phase HPLC, using a C18 column and a phosphate buffer-acetonitrile gradient. The phenolic compounds gallic acid, catechin, epicatechin, and ellagic acid were detected at 280 nm, caffeic acid, p-coumaric acid and trans-resveratrol at 313 nm, and rutin and quercitin were detected at 365 nm. All compounds were compared to authentic standard compounds. Preliminary results show that the concentrations of different phenolics vary widely in different fruits. Funding provided by the Department of Chemistry and Biochemistry, Cal Poly State University, San Luis Obispo.

Use of liquid chromatography–electrospray ionization tandem mass spectrometry to identify diarylheptanoids in turmeric ( Curcuma longa L.) rhizome

LC–ESI-MS/MS coupled to DAD analysis was used as an on-line tool for identification of diarylheptanoids in fresh turmeric rhizome extracts. Based on their mass spectra, from both negative and positive mode LC–ESI-MS/MS analysis, and supported by their DAD spectra, 19 diarylheptanoids were identified. Among these 19 compounds, curcumin, demethoxycurcumin, and bisdemethoxycurcumin were identified by comparing their chromatographic and spectral data with those of authentic standard compounds. The other diarylheptanoid compounds were identified or tentatively identified based on comparison to the three curcuminoids and each other. Twelve of the identified diarylheptanoids have not been previously reported from turmeric and six of these are new compounds.

Metabolic effects of intravenous LCT or MCT/LCT lipid emulsions in preterm infants

Most lipid emulsions for parenteral feeding of premature infants are based on long-chain triacylglycerols (LCTs), but inclusion of medium-chain triacylglycerols (MCTs) might provide a more readily oxidizable energy source. The influence of these emulsions on fatty acid composition and metabolism was studied in 12 premature neonates, who were randomly assigned to an LCT emulsion (control) or an emulsion with a mixture of MCT and LCT (1:1). On study day 7, all infants received [13C]linoleic (LA) and [13C]alpha-linolenic acid (ALA) tracers orally. Plasma phospholipid (PL) and triacylglycerol (TG) fatty acid composition and 13C enrichments of plasma PL fatty acids were determined on day 8. After 8 days of lipid infusion, plasma TGs in the MCT/LCT group had higher contents of C8:0 (0.50 +/- 0.60% vs. 0.10 +/- 0.12%; means +/- SD) and C10:0 (0.66 +/- 0.51% vs. 0.15 +/- 0.17%) than controls. LA content of plasma PLs was slightly lower in the MCT/LCT group (16.47 +/- 1.16% vs. 18.57 +/- 2.09%), whereas long-chain polyunsaturated derivatives (LC-PUFAs) of LA and ALA tended to be higher. The tracer distributions between precursors and products (LC-PUFAs) were not significantly different between groups. Both lipid emulsions achieve similar plasma essential fatty acid (EFA) contents and similar proportional conversion of EFAs to LC-PUFAs. The MCT/LCT emulsion seems to protect EFAs and LC-PUFAs from beta-oxidation.

Effect of Natural Light Periods on Rutin, Free Amino Acid and Vitamin C Contents in the Sprouts of Common (Fagopyrum esculentum Moench) and Tartary (F. tataricum Gaertn.) Buckwheats

Contents of rutin, free amino acids and vitamin C were measured with the sprouts of common buckwheat (Fagopyrum esculentum Moench, FE) and tartary buckwheat (F. tataricum Gaertn., FT), cultivated in darkness and/or under natural light conditions. Flavonoids, including rutin and quercetin were isolated from the sprouts of FE and FT by using HPLC and quantified with their authentic standard compounds. In FE sprouts, rutin content placed under natural light conditions was higher than from plants grown in darkness. In contrast, in FT sprouts rutin content was significantly affected both by days after seeding (DAS) and by lighting. On average, rutin content (55mg/g dry weight) of FT sprouts was 2.2-fold higher than that of FE sprouts. In both species, free amino acids levels were increased with increased natural light periods, and vitamin C content of the sprouts cultivated in darkness in both species was significantly lower than that of light-grown sprouts. Based on these characteristics, we concluded that the green sprouts of FT are a superior source of rutin, free amino acids and vitamin C. They could therefore be used as ‘functional foods’ fresh vegetables and freeze-dried powder.

Simultaneous analysis of N-nornuciferine, O-nornuciferine, nuciferine, and roemerine in leaves of Nelumbo nucifera Gaertn by high-performance liquid chromatography–photodiode array detection–electrospray mass spectrometry

A novel method has been developed for analysis of N-nornuciferine, O-nornuciferine, nuciferine, and roemerine in leaves of Nelumbo nucifera Gaertn by using high-performance liquid chromatography (HPLC)–photodiode array detection (DAD)–electrospray mass spectrometry (ESI-MS). The method was carried out by using a Shimadzu VP-ODS column with a gradient solvent system of 0.1% triethylamine aqueous solution–acetonitrile. N-Nornuciferine, O-nornuciferine, nuciferine, and roemerine were identified with authentic standard compounds and with MS-spectra. The contents of these compounds were measured by employing DAD. Linearity of around three orders in the magnitude of concentration was generally obtained and limits of detection for these compounds were in the range of 30–90 pg.

Simultaneous analysis of theanine, chlorogenic acid, purine alkaloids and catechins in tea samples with the help of multi-dimension information of on-line high performance liquid chromatography/electrospray–mass spectrometry

A reverse phase high performance liquid chromatography (RP-HPLC) separation coupled with photo diode array detection (DAD) and electrospray ionization mass spectrometry (ESI–MS) detection was established for the analyzing of multiple bioactive compounds in tea and tea extracts. Theanine, chlorogenic acid, purine alkaloids and catechins were identified with authentic standard compounds and with MS-spectra. The content of theanine and catechins was measured by employing DAD and caffeine, chlorogenic acid, theobromine and theopylline by protonated molecular ion on selective ion recording (SIR) mode. The unity of LC/ESI–MS provides more qualitative and quantitative information comparing with general HPLC in the analysis of multi-components in tea, and complex extraction or sample pretreatment is unnecessary. The chromatogram acquired by using this method can be used as a bioactive components fingerprint for the quality control of tea and its extracts. With the help of multi-dimension information of HPLC–DAD–ESIMS, the compounds owning different chemical structure such as amino acid, catechins, etc. in tea and its extracts could be identified and determined in one run successfully.

Microbial Transformations of Clomazone

Common soil fungi and bacteria were screened for their abilities to biotransform the herbicide clomazone (2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone) into metabolites. Preparative-scale incubations were conducted with Aspergillus niger (UI-X172) and Cunninghamella echinulata (NRRL-3655) to obtain metabolites in sufficient quantities for spectral and chromatographic identification. HPLC analyses were used to assess the capacities of 41 microorganisms to metabolize the herbicide. Based on comparisons with authentic standard compounds and on the structures of metabolites ascertained by 1H NMR and mass spectrometry, major microbial transformation reactions involved hydroxylation at the 5-methylene carbon of the isoxazolidone ring, hydroxylation of a methyl group on the oxazolidone ring, and aromatic hydroxylation at position 3‘. Minor metabolic routes included dihydroxylations of clomazone on the aromatic ring, cleavage of the isoxazolidone N−C bond, or complete removal of the isoxazolidone rin...

Microbial oxidation of oleic acid.

Resting cells of Saccharomyces cerevisiae (baker's yeast, type II; Sigma) were used to convert oleic acid into 10-hydroxyoctadecanoic acid with a 45% yield. Nocardia aurantia (ATCC 12674), Nocardia sp. (NRRL 5646), and Mycobacterium fortuitum (UI 53378) all converted oleic acid into 10-oxo-octadecanoic acid with 65, 55, and 80% yields, respectively. Structures of all metabolites were suggested by 1H and 13C nuclear magnetic resonance and by infrared and mass spectrometry. Structures of isomeric hydroxystearate and oxostearate derivatives and the stereochemical purity of hydroxystearates are difficult to prove unambiguously unless authentic standard compounds are available for spectral comparison. We describe the use of the chemical Baeyer-Villiger oxidation technique with 10-oxo-octadecanoic acid followed by mass spectral analysis of neutral extracts as a simple method to confirm the position of oxo-functional groups in the structures of fatty acid ketones. We further introduce a simple method based on 1H nuclear magnetic resonance analysis of diastereomeric S-(+)-O-acetylmandelate esters of hydroxystearates as a means of ascertaining stereochemical purities of hydroxy fatty acids.

Carbohydrates in humic and fulvic acids from Hiroshima Bay sediments

A core of 75 cm length from Hiroshima Bay, Seto Inland Sea in Japan, has been analyzed for the carbohydrate content of the humic and fulvic acids. These carbohydrates were found by gel filtration to be in the high molecular weight range. Carbohydrates were more abundant in fulvic acids than in humic acids. A comparison of carbohydrates in humic acids with those in fulvic acids showed that the former did not undergo diagenetic loss any faster than the latter. Identification of most alditol acetate in monosaccharides is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. However, the compositional differences between carbohydrates in humic and fulvic acids were greater in the top section of 0–20 cm than in the 50–70 cm section. The processes which produce the humic-acid carbohydrates are operative either prior to or shortly after deposition.

Fatty-acid methyl esters dissolved in seawater and associated with suspended particulate material

Methyl esters of saturated and unsaturated fatty acids were isolated as trace components from organic material suspended in seawater. Methyl palmitate and methyl stearate were accumulated from the filtrate by adsorption onto Amberlite XAD-2 resin. Identification of most methyl esters is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. In cases where reference substances were not available, identification is based on mass spectrometric and gas chromatographic properties of the unknown compounds.