Browsing by Author "Silva, J.A.L."
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- Assessment of the mercury-selenium antagonism in rainbow trout fishPublication . Ribeiro, M.; Zephyr, N.; Silva, J.A.L.; Danion, M.; Guérin, T.; Castanheira, I.; Leufroy, A.; Jitaru, P.This study aims at the assessment of mercury (Hg)-selenium (Se) antagonism in fish. For this purpose, rainbow trout fish (Oncorhynchus mykiss) were exposed to methylmercury (MeHg) under controlled conditions, in the presence or absence of selenomethionine (SeMet) using an in-house prepared diet (enriched with MeHg and SeMet at 0.2 μg/g and 5.0 μg/g, respectively). The total duration of the exposure study was 3 months. Fish was sampled and analysed for total Se (SeT) and total mercury (HgT) content after 1, 2 and 3 months of exposure. Six feeding protocols were compared, depending on the exposure type: (i) no MeHg nor SeMet exposure (control group); (ii) exposure to SeMet solely; (iii) exposure to MeHg solely; (iv) exposure to both MeHg and SeMet; (v) exposure first to MeHg during 1 month and then to SeMet during 2 months and (vi), exposure to SeMet during 1 month and then to MeHg for 2 months. The levels of SeT and HgT in the fish (control and supplemented with MeHg/SeMet) were measured by inductively coupled plasma-mass spectrometry (ICPMS). Steadily (linear) bioaccumulation of MeHg in the fish muscle occurred when the fish were exposed individually to this species during the period. The bioaccumulation of MeHg is diminished when the fish are firstly exposed to SeMet and then to MeHg, hence indicating the MeHg detoxification due to SeMet supplementation.
- Seasonal variation of chub mackerel (Scomber colias) selenium and vitamin B12 content and its potential role in human healthPublication . Rego, A.; Coelho, I.; Motta, C.; Cardoso, C.; Gomes-Bispo, A.; Afonso, C.; Prates, J.A.M.; Bandarra, N.M.; Silva, J.A.L.; Castanheira, I.Chub mackerel (Scomber colias), an underutilised fish species, has been identified as an excellent source of selenium and vitamin B12, which may prevent and delay cognitive decline and dementia. Given these nutrients’ contents seasonal variability, a complete monthly sampling, involving a specifically adjusted methodology for the determination of vitamin B12 (LC-MS/MS) and its main vitamers and a sensitive analytical technique (ICPMS) for Se, was carried out. Regarding total vitamin B12 in the chub mackerel muscle, its content varied from 10.0 ± 1.0 μg/100 g in February to 18.9 ± 1.9 μg/100 g in August. It was also shown that methylcobalamin content ranged from 1.12 ± 0.43 (March) to 6.77 ± 0.80 μg/100 g (August), a sixfold increase. Hydroxocobalamin content varied between 3.49 ± 0.12 (February) and 9.62 ± 0.41 μg/100 g (August). The content of Se also had seasonal variability, ranging from 451 ± 14 μg/kg (December) to 606 ± 11 μg/kg (July). In the worst-case scenario, a weekly 160 g meal of this fish would almost guarantee B12 requirements. Three weekly 160 g meals of S. colias would cover, at least, 56% of the Se requirements. Therefore, as first explored here, it is highly relevant a complete, year-round assessment of the chub mackerel’s nutritional value, in order to elaborate finely tuned dietary recommendations.
- Simultaneous speciation analysis of Hg and Se in fish by high-performance liquid chromatography and inductively coupled plasma-mass spectrometry following microwave-assisted enzymatic hydrolysisPublication . Ribeiro, M.; Galli, E.; Guérin, T.; Silva, J.A.L.; Castanheira, I.; Leufroy, A.; Jitaru, P.This study reports the development and validation of a new analytical method for simultaneous speciation analysis of Se and Hg in fish muscle. For this purpose, four Se species (selenite/Se(IV), selenate/Se(VI), selenomethionine/SeMet, and selenocysteine/SeCys) and two Hg species (inorganic mercury/iHg and methylmercury/MeHg) were extracted simultaneously by microwave-assisted enzymatic hydrolysis and then separated by HPLC in less than 15 min by using a column with both anion and cation exchange mechanisms and a mobile phase consisting of a mixture of methanol 5% (v/v), 45 mM HNO3, 0.015% 2-mercaptoethanol, and 1.5 mM sodium 3-mercapto-1-propanesulfonate. The separated species of Hg and Se were detected online by inductively coupled plasma-mass spectrometry (ICP-MS). The speciation analysis method was validated by means of the accuracy profile approach by carrying out three series of measurements in duplicate on three different days over a time-span of 3 weeks. The limits of quantification (LOQ) are in the range of 0.010–0.013 mg/kg wet weight (ww) for all selenium species, except for Se(IV) (0.15 mg/kg ww), while the coefficient of variation in terms of intermediate reproducibility (CVR) was < 7%. The LOQ for MeHg was 0.006 mg/kg ww, while the CVR was 3%. The method was successfully applied to the analysis of muscle samples from four different fish species: rainbow trout, tuna, swordfish, and dogfish.