Determination of tylosins A, B, C and D in bee larvae by liquid chromatography coupled to ion trap-tandem mass spectrometry.

A LC-MS/MS method has been developed to simultaneously quantify tylosins A, B, C and D in bee larvae, compounds currently used to treat one of the most lethal diseases affecting honey bees around the world, American Foulbrood (AFB). The influence of different aqueous media, temperature and light exposure on the stability of these four compounds was studied. The analytes were extracted from bee larvae with methanol and chromatographic separation was achieved on a Luna C(18) (150 × 4.6 mm i.d.) using a ternary gradient composed of a diluted formic acid, methanol and acetonitrile mobile phase. To facilitate sampling, bee larvae were initially dried at 60°C for 4h and afterwards, they were diluted to avoid problems of pressure. MSD-Ion Trap detection was employed with electrospray ionization (ESI). The calibration curves were linear over a wide range of concentrations and the method was validated as sensitive, precise and accurate within the limits of quantification (LOQ, 1.4-4.0 ng/g). The validated method was successfully employed to study bee larvae in field tests of bee hives treated with two formulations containing tylosin. In both cases it was evident that the minimal inhibitory concentration (MIC) had been reached.

Quality assurance of commercial beeswax. Part I. Gas chromatography-electron impact ionization mass spectrometry of hydrocarbons and monoesters.

The use of low-temperature capillary gas chromatography coupled to electron impact mass spectrometry for the characterization of crude beeswaxes yielded by Apis mellifera is described. The system allows the identification of a great number of compounds, some of them not reported till now in beeswax, such as a family of ethyl esters, tetracosyl oleate, and several saturated and unsaturated hydrocarbons. The information acquired makes possible the differentiation between pure beeswax and some foundation beeswax samples where mixture of pure beeswax with another substances is suspected.

[Influence of biochemical and genetic factors on homocysteine concentrations]. / Influencia de factores bioquímicos y genéticos en las concentraciones de homocisteína.

BACKGROUND: Several studies have examined the association between the methylenetetrahydrofolate reductase (MTHFR) genotype and plasma homocysteine concentrations in adults but few studies have been performed in children. OBJECTIVE: To determine plasma concentrations of total homocysteine, folate, vitamin B12, and red cell folate in a group of healthy children and to determine their possible relationship with the MTHFR genotype. SUBJECTS AND METHODS: Eighty-three subjects (45 boys and 38 girls), aged between 1 week and 18 years, were included in the study. Plasma and whole blood samples were stored at 80 C for biochemical and molecular analysis. Plasma total homocysteine was determined by fluorescence polarization immunoassay. Serum concentrations of folate, vitamin B12, and red cell folate were measured by electrochemiluminescence immunoassay. Genotypic analysis was performed by polymerase chain reaction amplification of genomic DNA extracted from blood leukocytes. RESULTS: Plasma homocysteine concentrations were negatively correlated with folate, vitamin B12, and red cell folate but were positively correlated with age (p < 0.005). There was an association between age-MTHFR genotype and folic acid, vitamin B12, and red cell folate, but not with homocysteine concentrations. CONCLUSIONS: Our results suggest that in a healthy pediatric population, homocysteine concentrations are determined by biochemical factors, such as folic acid, more than by genetic factors.