Urinary Excretion of Niacin Metabolites in Humans After Coffee Consumption.

SCOPE: Coffee is a major natural source of niacin in the human diet, as it is formed during coffee roasting from the alkaloid trigonelline. The intention of our study was to monitor the urinary excretion of niacin metabolites after coffee consumption under controlled diet. METHODS AND RESULTS: We performed a 4-day human intervention study on the excretion of major niacin metabolites in the urine of volunteers after ingestion of 500 mL regular coffee containing 34.8 µmol nicotinic acid (NA) and 0.58 µmol nicotinamide (NAM). In addition to NA and NAM, the metabolites N1 -methylnicotinamide (NMNAM), N1 -methyl-2-pyridone-5-carboxamide (2-Py), and nicotinuric acid (NUA) were identified and quantified in the collected urine samples by stable isotope dilution analysis (SIVA) using HPLC-ESI-MS/MS. Rapid urinary excretion was observed for the main metabolites (NA, NAM, NMNAM, and 2-Py), with tmax values within the first hour after ingestion. NUA appeared in traces even more rapidly. In sum, 972 nmol h-1 of NA, NAM, NMNAM, and 2-Py were excreted within 12 h after coffee consumption, corresponding to 6% of the ingested NA and NAM. CONCLUSION: The results indicate regular coffee consumption to be a source of niacin in human diet.

Comparison of the circulating metabolite profile of PF-04991532, a hepatoselective glucokinase activator, across preclinical species and humans: potential implications in metabolites in safety testing assessment.

A previous report from our laboratory disclosed the identification of PF-04991532 [(S)-6-(3-cyclopentyl-2-(4-trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic acid] as a hepatoselective glucokinase activator for the treatment of type 2 diabetes mellitus. Lack of in vitro metabolic turnover in microsomes and hepatocytes from preclinical species and humans suggested that metabolism would be inconsequential as a clearance mechanism of PF-04991532 in vivo. Qualitative examination of human circulating metabolites using plasma samples from a 14-day multiple ascending dose clinical study, however, revealed a glucuronide (M1) and monohydroxylation products (M2a and M2b/M2c) whose abundances (based on UV integration) were greater than 10% of the total drug-related material. Based on this preliminary observation, mass balance/excretion studies were triggered in animals, which revealed that the majority of circulating radioactivity following the oral administration of [¹4C]PF-04991532 was attributed to an unchanged parent (>70% in rats and dogs). In contrast with the human circulatory metabolite profile, the monohydroxylated metabolites were not detected in circulation in either rats or dogs. Available mass spectral evidence suggested that M2a and M2b/M2c were diastereomers derived from cyclopentyl ring oxidation in PF-04991532. Because cyclopentyl ring hydroxylation on the C-2 and C-3 positions can generate eight possible diastereomers, it was possible that additional diastereomers may have also formed and would need to be resolved from the M2a and M2b/M2c peaks observed in the current chromatography conditions. In conclusion, the human metabolite scouting study in tandem with the animal mass balance study allowed early identification of PF-04991532 oxidative metabolites, which were not predicted by in vitro methods and may require additional scrutiny in the development phase of PF-04991532.

[Detection of chloropyridinyl neonicotinoid insecticide metabolite 6-chloronicotinic acid in the urine: six cases with subacute nicotinic symptoms].

Neonicotinoid is a recently developed insecticide with worldwide use that has been increasing. It acts as a nicotinic acetylcholine receptor agonist. Chloropyridinyl neonicotinoid is a subgroup of neonicotinoid, and are commercially available as imidacloprid, nitenpyram, acetamiprid, and thiacloprid. The maximum residue limits of acetamiprid for fruits and tea leaves are high in Japan, e.g. 5 ppm for grapes and 30 ppm for tea leaves. 6-chloronicotinic acid (6 CNA) is a common metabolite in animals after exposure to chloropyridinyl neonicotinoids, but has not yet been detected in human urine. 'Spot' urine samples on the first visit and after were collected from eleven patients 6-52 years-old, who visited X-clinic from August to December in 2008, within 24 hours after symptom onset with unknown origin. Urinary 6 CNA was detected in six out of the eleven patients (IC positive group), by ion chromatography and identified in twenty specimens of these six patients by liquid chromatography-mass spectrometry (LC/MS), maximum 84.8 microg/L from the first visit to the 20th visit. The sensitivity of ion chromatography for LC/MS was 45%, and the specificity was 100%. The IC positive group showed headache, general fatigue, finger tremor, and short time memory disturbance in 100%, fever (> 37.0 degrees C), cough, palpitation, chest pain, stomachache, myalgia/muscle spasm/muscle weakness in 83%, heart rate abnormality (sinus tachycardia, sinus bradycardia, or intermittent WPW syndrome) in 83%, high domestic fruits intake (> 500 g/day) in 83%, high tea beverage intake (> 500 mL/day) in 66%. Five patients who were not among the IC positive group showed < 80%, < 40%, 60%, 60%, 20%, respectively. The patients gradually recovered through supportive therapy and the restriction of fruits and tea intake within several days to two months. In conclusion, urinary 6-chloronicotinic acid, a common metabolite of chloropyridinyl neonicotinoid insecticide, was detected for the first time, from six patients with subacute nicotinic symptoms.

Identification of N1-methyl-2-pyridone-5-carboxamide and N1-methyl-4-pyridone-5-carboxamide as components in urine extracts of individuals consuming coffee.

Caffeine metabolites were extracted from urine samples collected 4 h after consumption of a cup of coffee and were separated by high-performance liquid chromatography (HPLC) on a C18 (5 microm) reverse-phase column using an acetonitrile (5%), acetic acid (0.05%) solution as the mobile phase. The elution profiles indicated the constant presence of a major and a minor components eluting between the caffeine metabolites 5-acetamido-6-formyl-3-methyluracil (AFMU) and 7-methylxanthine (7X) in an approximate nine. A procedure was developed for the isolation of the major component in an apparent pure form, and the yield was 10-20 mg from 400 ml of urine. The minor component was isolated in an apparent pure form by this procedure as well, and the yield was 0.5 mg from 200 ml of urine. The average ratio of the two components in urine, UV absorption and 1H-NMR spectra of the two components, and 13C-NMR spectrum, mass spectrum and elemental analysis of the major component identified the major and minor components as N(1)-methyl-2-pyridone-5-carboxamide and N(1)-methyl-4-pyridone-5-carboxamide, respectively, two major metabolites of the vitamin niacin present in a significant amount in coffee beans. The two metabolites were present in the same average amount in urine extracts of individuals irregardless of coffee consumption. The findings are briefly discussed in relation to the nutritional sources of niacin and to current procedures for measuring amounts of the two metabolites in urine samples.

The role of column switching in analysing complex samples.

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful methods. Multiple zone cutting is also possible to further increase to scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.

Niacin and pantothenic acid excretions of humans fed a low-methionine, plant-based diet.

The addition of a vitamin to a diet of humans has been shown to increase the excretion of that vitamin. The effects of an increase of one vitamin on another have not been investigated. The objective of the current project was to compare the effects of two supplementation patterns on the niacin and pantothenic acid excretion values of humans consuming a peanut butter-based diet. Two groups each received one of two supplementation regimens. One group received niacin, a multi-vitamin, or no supplement. One group received methionine alone, pantothenic acid alone or methionine plus pantothenic acid. The addition of either vitamin resulted in increased excretion of that vitamin. Urinary niacin excretion of the group that received pantothenic acid and/or methionine was greater than that observed with a multi-vitamin or no supplement. Urinary pantothenic acid excretion was suppressed when niacin was a supplement. Urinary pantothenic acid excretion of the methionine supplement group was greater than the excretion of the groups which received either niacin or multi-vitamin supplements. These data suggest some possible dangers in indiscriminate supplementation of food products.