Development of a LC-MS/MS method using stable isotope dilution for the quantification of individual B6 vitamers in fruits, vegetables, and cereals.

Vitamin B6 comprises an important set of molecules tightly interwoven with the human amino acid, fatty acid, and carbohydrate metabolism. Analytical methods striving for the quantification of individual B6 vitamers so far mostly rely on methods based on HPLC in combination with fluorescence detection, but their application encounters multiple difficulties due to the chemical divergence of the single vitamers. The present study describes the development of a method based on LC-MS/MS and stable isotope dilution assay (SIDA) for the simultaneous quantification of five vitamers (PN, PL, PM, PMP, and PNG) of the B6 group in food samples. [13C3]-PN, [13C3]-PL, and [13C6]-PNG were applied as internal standards for the analysis of PN, PL, and PNG. PM and PMP were quantified via matrix-matched calibration referring to [13C3]-PN. The developed method was validated using starch matrix. The limits of detection and quantification ranged from 0.0028 to 0.02 mg/kg and from 0.0085 to 0.059 mg/kg, respectively, for all analytes. Calculated recoveries varied from 92 to 111%. Intra-injection precisions ranged from 0 to 9%, inter-day precisions from 4 to 10%, and intra-day precisions from 4 to 10%. A total of 14 plant-based food samples including fruits, vegetables, and cereals were examined for their content of vitamin B6 using the validated method. Furthermore, the first quantitation of PNG without enzymatic steps or divergent internal standards was undertaken utilizing LC-MS/MS and SIDA.

Effect of different methods of thermotherapy on skin microcirculation.

OBJECTIVE: The purpose of the study was to compare the effects of different methods of thermotherapy on skin microcirculation, skin temperature, and core temperature in patients with rheumatoid arthritis and in healthy persons. DESIGN: In 20 patients with rheumatoid arthritis and 20 healthy controls, the skin microcirculation was measured by means of laser-Doppler flowmetry before, at the end of, and 30 mins after completion of local thermotherapy (infrared light, paraffin, peat) in the lumbar area. In addition, skin and core temperature were recorded at the same point in time. The influence of previous intake of acetylsalicylic acid on skin microcirculation during thermotherapy was investigated. The controlled trial was conducted in an air-conditioned laboratory. RESULTS: All methods caused a significant increase in skin microcirculation (flow and vasomotion), skin temperature, and core temperature. The skin temperature showed the highest increase when infrared light was applied. The microcirculation became more intense when paraffin fango was used. There were no differences between the reactions of rheumatoid arthritis patients and healthy persons. The additional intake of 500 mg acetylsalicylic acid before treatment did not affect skin temperature or skin microcirculation. A tendency toward a sinusoidal rhythmization of vasomotion was detected. CONCLUSIONS: The effects of the three methods of thermotherapy differ quantitatively due to their physical attributes. The effects on circulation differ depending on the method chosen, and this is significant when selecting the least stressful method for a particular patient. Rheumatoid arthritis patients and healthy controls have the same increase of skin microcirculation in the lumbar area. Findings in the distal limbs might differ. All used therapies cause a rhythmization of the vasomotion and, as a consequence, a qualitative improvement of the microcirculation.