Jodie V. Johnson

Flavanone absorption after naringin, hesperidin, and citrus administration

Disposition of citrus flavonoids was evaluated after single oral doses of pure compounds (500 mg naringin and 500 mg hesperidin) and after multiple doses of combined grapefruit juice and orange juice and of once‐daily grapefruit. Cumulative urinary recovery indicated low bioavailability (<25%) of naringin and hesperidin. The aglycones naringenin and hesperitin were detected in urine and plasma by positive chemical ionization‐collisionally activated dissociation tandem mass spectrometry (PCI‐CAD MS/MS). After juice administration, PCI‐CAD MS/MS detected naringenin, hesperitin, and four related flavanones, tentatively identified as monomethoxy and dimethoxy derivatives. These methoxyflavanones appear to be absorbed from juice. Absorbed citrus flavanones may undergo glucuronidation before urinary excretion.

Nonlinear resonance effects during ion storage in a quadrupole ion trap

Contributions of higher-order fields to the quadrupolar storage field produce nonlinear resonances in the quadrupole ion trap. Storing ions with secular frequencies corresponding to these nonlinear resonances allows absorption of power from the higher-order fields. This results in increased axial and radial amplitudes which can cause ion ejection and collision-induced dissociation (CID). Experiments employing long storage times and/or high ion populations, such as chemical ionization, ion-molecule reaction studies, and resonance excitation CID, can be particularly susceptible to nonlinear resonance effects. The effects of higher-order fields on stored ions are presented and the influence of instrumental parameters such as radiofrequency and direct current voltage (qZ and az values), ion population, and storage time are discussed.

Mass-selection of reactant ions for chemical ionization in quadrupole ion trap and triple quadrupole mass spectrometers

Abstract Charge exchange (CE), proton transfer, and hydride abstraction chemical ionization (CI) were examined as selective modes of ionization. The utility of mass selecting reactant ions for CI has been demonstrated with a quadrupole ion trap (QITMS) and a triple quadrupole mass spectrometer (TQMS). The instrumental parameters that allow mass-selection of reactant ions are addressed. The non-mass-selected and mass-selected CI results are compared and the advantages of mass-selected CI are discussed. A comparison between mass-selected CI on the QITMS and TQMS is also made. Finally, the ability to determine ionization energies rapidly and simply on a computer-controlled TQMS is demonstrated.

MS-MS parent scans on a quadrupole ion trap mass spectrometer by simultaneous resonant excitation of multiple ions

Abstract A parent ion scan has been developed for a quadrupole ion trap mass spectrometer (ITMS) which makes it possible to obtain a conventional parent ion spectrum following a single ionization event. Two resonant excitation waveforms were applied simultaneously across the end-cap electrodes of an ITMS. One of the resonant excitation waveforms is applied at a frequency and voltage chosen to cause rapid ejection of a selected daughter ion. The frequency of the second waveform is scanned to induce sequentially resonant excitation collision-induced dissociation (CID) of a series of parent ions. Those ions which undergo CID to produce the selected daughter ion will be detected as parent ions.

Concentrations of Tryptoline and Methtryptoline in Rat Brain

Abstract: Combined gas chromatography‐mass spectrometry and gas chromatography‐tandem mass spectrometry have been used to identify and quantify tryptoline, methtryptoline, 5‐hydroxytryptoline, and 5‐hydroxymethtryptoline as their heptafluorobutyryl derivatives in extracts of rat brain. Tryptoline and methtryptohne were identified on the basis of their retention times and mass spectral characteristics: they were reliably detected in brain tissue extracts without interference from artifactual formation; their whole brain concentrations ranged between 0.2 and 3 ng/g; and they had a similar neu‐roanatomical distribution, with the highest concentrations in the cerebellum and the cortex. Smaller quantities of 5‐hydroxytryptoline and 5‐hydroxymethtryptoline were also identified on the basis of their retention times and mass spectral characteristics. However, the significance of this finding is unclear, because these two compounds were accompanied by larger quantities of their tetradeuterated analogues formed from tetradeuterated‐5‐hydroxytryptamine added at the time of tissue homogenization; this result suggests that formation of 5‐hydroxytryptoline and 5‐hydroxymethtryptoline occurred during tissue homogenization, sample preparation, or both.

Pharmaceutical and clinical analysis by tandem mass spectrometry

Tandem mass spectrometry (MS/MS) is a promising technique for trace determination of compounds in complex mixtures. The application of triple-quadrupole MS/MS to clinical and pharmacological studies has been investigated with major emphasis on rapid screening and determination of drugs and biomolecules in physiological fluids and tissues. These techniques have been applied to a range of problems, including the determination of chlorinated compounds in humans, subpicogram analysis of neurochemicals and the detection of illegal drugs in racing animals. A new technique for determining the structures of all the metabolites of a particular drug has also been developed. It is possible to identify in a single sample all molecular ions which contain substructures characteristic of the parent drug. The structure of each metabolite can then be determined by obtaining the MS/MS spectrum of the molecular ion.

Studies on high carbon number geoporphyrins by tandem mass spectrometry

Abstract High carbon number geoporphyrins (>C 33 ) aetio and DPEP porphyrins were isolated from Boscan oil (Cretaceous, W. Venezuela) and analysed by tandem mass spectrometry (MS/MS). The results provide the first structural information on individual high carbon number porphyrins which were not generated from chlorobium chlorophylls. These porphyrins are present in high abundance, ca 25% of the total geoporphyrin content. There are a number of isomers of both aetio and DPEP porphyrins present, but there is a marked difference between the isomeric composition of the two classes. In addition to the true DPEP components, other geoporphyrins which bear an isocyclic ring may also be abundant. There are at least two sites on the chlorophyll a macrocycle which can be converted to extended (>C 2 ) alkyl substituents assuming that it is the precursor of the geoporphyrins.

Microwave-Assisted Solid-Phase Peptide Synthesis Utilizing N-Fmoc-Protected (α-aminoacyl)benzotriazoles

A novel microwave‐assisted solid‐phase peptide synthesis utilizing N‐Fmoc‐protected(α‐aminoacyl)benzotriazoles was applied in the preparation of tri‐, tetra‐, penta‐, hexa‐, and heptapeptides in 71% average crude yield.

Comparative Metabolism and Toxicokinetics of 14C-ResorcinoI Bis-Diphenylphosphate (RDP) in the Rat, Mouse, and Monkey

As part of a comprehensive program to examine the safety and toxicokinetics of the flame retardant, resorcinol bis-diphenylphosphate (RDP), the metabolism and toxicokinetics of RDP was determined after exposure of rats and monkeys to 14C-RDP via intravenous, inhalation, oral, or dermal routes. The metabolism of RDP was also determined in mice. Blood, urine, and fecal samples were collected at specified times for the quantification of 14C levels. Expired air was collected from rats. Excreta samples were quantitatively extracted. Chromatographic profiles of urinary and fecal metabolites were generated for multiple animals from each group. The major metabolites were isolated and then purified by a multistep chromatographic process. Structures of urinary and fecal metabolites were determined by HPLC-mass spectrometry (MS), MS-MS, and MS-MS-MS techniques. The metabolic pattern in all three species is complex. In certain urine and feces samples, radioactivity was associated with more than 30 HPLC peaks. There was little interanimal variability in metabolic profiles. No differences between species or sexes were apparent. The parent molecule, RDP, was present in significant amounts only in the feces of animals exposed by inhalation or gavage; this appears to reflect unabsorbed ingested material. Structures of all major urinary and fecal metabolites (representing 5% of the administered dose) in rats and primates were identified. The major fecal metabolites were resorcinol diphenylphosphate (RDP half ester), hydroxy-RDP half ester, dihydroxy-RDP, and hydroxy-RDP. Major urinary metabolites were identified as resorcinol, resorcinyl glucuronide, and resorcinyl sulfate. A small amount of 14CO2 was expired. This study confirms that RDP is metabolized in an identical manner by rats, mice, and primates, and that the rat and mouse are appropriate surrogates (animal models) in which to assess the toxicity of RDP. In both rats and primates, the highest peak plasma concentration (Cmax) and greatest area under the curve (AUC) was obtained with intravenous (TV) administration. In rats the Cmax for inhalation, oral, and dermal exposures were 42%, 10%, and 1%, respectfully. The AUC values for these three routes were 60%, 58%, and 15% of the IV AUC. Approximately 20% of the dermal dose was absorbed in the rat whereas primates absorbed only 10% of the applied dermal dose. Tissue accumulation and retention of radioactivity was minimal, indicating complete clearance of the administered dose.

Bilirubin present in diverse angiosperms.

Recently, we discovered bilirubin-IXα, a pigment previously known only in animals as a breakdown product of heme, in Strelitzia nicolai. Here, we show that bilirubin-IXα is present in eight species from three diverse angiosperm orders.