4 research outputs found
High-Throughput Quantitation of Proline Betaine in Foods and Suitability as a Valid Biomarker for Citrus Consumption
Proline
betaine has been proposed as a candidate dietary biomarker
for citrus intake. To validate its suitability as a dietary biomarker
and to gain insight into the range of this per-methylated amino acid
in foods and beverages, a quick and accurate stable isotope dilution
assay was developed for quantitative high-throughput HILIC-MS/MS screening
of proline betaine in foods and urine after solvent-mediated matrix
precipitation. Quantitative analysis of a variety of foods confirmed
substantial amounts of proline betaine in citrus juices (140â1100
mg/L) and revealed high abundance in tubers of the vegetable Stachys affinis, also known as Chinese artichocke
(âŒ700 mg/kg). Seafood including clams, shrimp, and lobster
contained limited amounts (1â95 mg/kg), whereas only traces
were detected in fish, cuttlefish, fresh meat, dairy products, fresh
vegetable (<3 mg/kg), coffee, tea, beer, and wine (<7 mg/L).
The human excretion profiles of proline betaine in urine were comparable
when common portions of orange juice or fried <i>Stachys</i> tubers were consumed. Neither mussels nor beer provided enough proline
betaine to detect significant differences between morning urine samples
collected before and after consumption. As <i>Stachys</i> is a rather rare vegetable and not part of peoplesâ daily
diet, the data reported here will help to monitor the subjectâs
compliance in future nutritional human studies on citrus products
or the exclusion of citrus products in the wash-out phase of an intervention
study. Moreover, proline betaine measurement can contribute to the
establishment of a toolbox of valid dietary biomarkers reflecting
wider aspects of diet to assess metabolic profiles as measures of
dietary exposure and indicators of dietary patterns, dietary changes,
or effectiveness of dietary interventions
Mozambioside Is an Arabica-Specific Bitter-Tasting Furokaurane Glucoside in Coffee Beans
Sensory-guided
fractionation of a roasted coffee beverage revealed
a highly polar, bitter-tasting subfraction, from which the furokaurane
glucoside mozambioside was isolated and identified in its chemical
structure by means of HDMS and NMR spectra. Sensory evaluation revealed
a bitter taste recognition threshold of 60 (±10) Όmol/L.
UPLC-HDMS quantitation of raw coffee beans showed that Arabica coffees
contained 396â1188 nmol/g mozambioside, whereas only traces
(<5 nmol/g) were detected in Robusta coffees, thus suggesting that
mozambioside can be used as an analytical marker for Arabica coffee.
Roasted Arabica contained a substantially reduced concentration (232
± 37 nmol/g), indicating partial degradation of mozambioside
during coffee roasting. Mozambioside was nearly quantitatively extracted
into the aqueous brew during coffee-making (86â98%)
Metabolites of Key Flavor Compound 2,3,5-Trimethylpyrazine in Human Urine
Pyrazines are among the most important compound class
conveying
the odor impressions âroastyâ, ânuttyâ,
and âearthyâ. They are formed by the Maillard reaction
and occur ubiquitously in heated foods. The excretion of metabolites
of the key flavor odorant 2,3,5-trimethylpyrazine, abundant in the
volatile fraction of roasted coffee, was investigated. Based on literature
suggestions, putative phase 1 and phase 2 metabolites were synthesized,
characterized by nuclear magnetic resonance and mass spectroscopy
data and used as standards for targeted, quantitative analysis of
coffee drinkersâ urine using stable-isotope-dilution-ultrahigh-performance
liquid chromatography tandem mass spectroscopy (SIDA-UHPLCâMS/MS).
The analysis of spot urine samples from a coffee intervention study
revealed 3,6-dimethylpyrazine-2-carboxylic acid, 3,5-dimethylpyrazine-2-carboxylic
acid, and 5,6-dimethylpyrazine-2-carboxylic acid were quantitatively
dominating metabolites. Only negligible traces of pyrazinemethanols
(3,6-dimethyl-2-pyrazinemethanol and 3,5,6-trimethylpyrazine-2-ol),
glucuronides ((3,6-dimethylpyrazine-2-yl-)methyl-O-ÎČ-D-glucuronide
and (3,5-dimethylpyrazine-2-yl-)methyl-O-ÎČ-D-glucuronide), and
sulfates ((3,6-dimethylpyrazine-2-yl-)methyl-sulfate and (3,5-dimethylpyrazine-2-yl-)methyl-sulfate)
were detected
Development and Application of a Stable Isotope Dilution Analysis for the Quantitation of Advanced Glycation End Products of Creatinine in Biofluids of Type 2 Diabetic Patients and Healthy Volunteers
<i>N</i>-(1-Methyl-4-oxoimidazolidin-2-ylidene)
α-amino
acids were recently identified in roasted meat as so far unknown advanced
glycation end products (AGEs) of creatinine. For the first time, this
paper reports on the preparation of <sup>13</sup>C-labeled twin molecules
of six <i>N</i>-(1-methyl-4-oxoimidazolidin-2-ylidene) α-amino
acids and the development of a stable isotope dilution analysis (SIDA)
for their simultaneous quantitation in meat, plasma, and urine samples
by means of HPLC-MS/MS. Method validation demonstrated good precision
(<14% RSD) and accuracy (97â118%) for all analytes and a
lower limit of quantitation of 1 pg injected onto the column. The
SIDA was applied to monitor plasma appearance and urinary excretion
of these AGEs in type 2 diabetes mellitus patients (DM, <i>n</i> = 7) and healthy controls (<i>n</i> = 10) prior to and
after ingestion of a bolus of processed beef meat. Interestingly,
the basal concentration of <i>N</i>-(1-methyl-4-oxoimidazolidin-2-ylidene)
aminopropionic acid was elevated in plasma and urine of DM patients
compared to healthy individuals. Further, ingestion of processed meat
led to a significantly higher concentration of this AGE in biofluids
from DM patients when compared to healthy controls. These findings
suggest a favored in vivo formation, as demonstrated by physiological
model incubations of creatinine and carbohydrates (37 °C, pH
7.4), or a more efficient dietary up-take of <i>N</i>-(1-methyl-4-oxoimidazolidin-2-ylidene)
α-amino acids in hyperglycemic diabetes patients