Plasma allantoin measurement by isocratic liquid chromatography with tandem mass spectrometry: method evaluation and application in oxidative stress biomonitoring.

Background: Allantoin in human plasma is a specific biomarker of oxidative stress. We describe a sensitive method to measure plasma allantoin using isocratic liquid chromatography and mass spectrometry (LC-MS/MS).

Methods: Direct injection of deproteinized plasma into the LC-MS/MS system was performed.

Comparison of catechin profiles in human plasma and urine after single dosing and regular intake of green tea (Camellia sinensis).

Green tea (Camellia sinensis) catechin profiles in plasma and urine following single dosing and regular ingestion of green tea are not clear. We performed a placebo-controlled intervention study with sixteen healthy volunteers to determine changes in total and free catechins after a single dose and following 1 week of twice-daily green tea. Blood and urine samples were collected before (fasting) and after (60 and 120 min for blood; 90 and 180 min for urine) drinking 200 ml of 1.

Colour additives in snack foods consumed by primary school children in Hong Kong.

The objective of the present study was to assess synthetic colours in common snack foods consumed by children and the accuracy of labelling. Dietary exposure to synthetic colours was estimated using food frequency questionnaire data obtained from primary school children in Hong Kong. The concentration of synthetic colours in food items consumed was determined by HPLC with photodiode array detection.

Urine 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a specific marker of oxidative stress, using direct, isocratic LC-MS/MS: Method evaluation and application in study of biological variation in healthy adults.

Background: Urine 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is a specific biomarker of oxidative stress. We evaluated a modified LC-MS/MS assay for urine 8-oxodG and determined biological variation in healthy adults.

Method: Untreated urine was injected into an isocratic LC-MS/MS system (positive-ion MRM mode).

Fasting plasma zeaxanthin response to Fructus barbarum L. (wolfberry; Kei Tze) in a food-based human supplementation trial.

Age-related macular degeneration (AMD) is a common disorder that causes irreversible loss of central vision. Increased intake of foods containing zeaxanthin may be effective in preventing AMD because the macula accumulates zeaxanthin and lutein, oxygenated carotenoids with antioxidant and blue light-absorbing properties. Lycium barbarum L.

Reflex tear ascorbate in Hong Kong Chinese subjects: method comparison and biological variation.

Background: Tear ascorbate is important for corneal health. A rapid and simple method for measurement of ascorbate in tears is needed, and adequate knowledge of physiological variation of tear ascorbate is important to facilitate comparative studies of the effect of, for example, contact lens wear and environmental conditions and stresses. However, there are currently no data on physiological variation of tear ascorbate.