Jun Yonekubo

Sensitive method for the determination of bisphenol-A in serum using two systems of high-performance liquid chromatography.

The aim of this study was to establish an easy and accurate method for the determination of bisphenol-A (BPA) in the body liquid such as serum and urine. Two high-performance liquid chromatography (HPLC) systems, HPLC with electrochemical detector (ED), and HPLC with mass spectrometry (MS) using electrospray ionization (ESI) interface were used for the assay in the serum samples prepared with solid-phase extraction method. Water or EtOH at a concentration below 50% was suitable for the extraction of BPA from serum. The limit of detection of BPA was 0.2 ng ml(-1) for the HPLC-ED method and 0.1 ng ml(-1) for HPLC-MS. There was a good correlation between the data obtained by the two HPLC systems. BPA concentrations in healthy human serum were low (0-1.6 ng ml(-1)). From various commercial fetal bovine serum and sheep plasma, however, significant amounts of BPA were detected. Since no BPA was detected from sheep plasma immediately after collection, the high amounts of BPA were considered to be caused by the handling of blood during the preparation of the products after blood collection. In vitro study showed that the amount of BPA leached from polycarbonate tube into sheep plasma were 40 times larger than those into water and the leached amount of BPA depended on the temperature (37 degrees C>20 degrees C>5 degrees C).

Leaching of bisphenol A (BPA) to seawater from polycarbonate plastic and its degradation by reactive oxygen species.

In this study, (1) change in the concentration of bisphenol A (BPA) leached from polycarbonate (PC) tube to control water (BPA free), seawater and river water at 20 and 37 degrees C as a function of time, (2) the fate of BPA caused by addition of H(2)O(2) and Fe(3+) to seawater containing BPA leached from PC tube were assessed. BPA leached from PC tube to all water samples increased with the ascendant of temperature and with the passage of time. The BPA leaching velocity in seawater was the fastest in three samples (11 ng/day for seawater, 4.8 ng/day for river water 0.8 ng/day for control water at 37 degrees C).BPA leaching velocity from PC tube was significantly high at pH 8 (50 mM Na(2)HPO(4)) and increased dose-dependently. There was no difference in the velocity of BPA among the 50 mM phosphate-buffers at pH 6.5, 7.0 and 7.5. BPA was leached three times higher by addition of Na(+) than K(+). However, the higher the K(+) concentration, the larger the BPA leached from PC tube. Na(+) mixed with PO(4)(-) was effective on BPA leaching from PC tube, but not with SO(4)(-) or Cl(-). The results suggested that BPA leaching from PC tube would be attributed to the concentration of bibasic phosphate such as Na(2)HPO(4) and K(2)HPO(4) in water samples. BPA was degraded in both control water and seawater in the presence of radical oxygen species, but the degradation rate was lower in seawater than in control water, suggesting that anti-oxidative system exists in seawater. Neo-synthesized substance in both control water and seawater in the presence of reactive oxygen species was identified as BPA-quinone by LC-MS.

Bisphenol A (BPA) and its source in foods in Japanese markets

The determination of bisphenol A (BPA) and/or bisphenol A diglycidyl ether (BADGE) in foods sold in Japanese markets and in water leached from six epoxy resin cans with similar diameters was carried out using high-performance liquid chromatography (HPLC) with electrochemical detection (LC/ECD), LC-mass spectrometric detection (LC/MS) and LC-tandem mass spectrometric detection (LC/MS/MS). BPA concentrations were 0–842 ng g−1 for 48 canned foods, 0–14 ng g−1 for 23 foods in plastic containers, and 0–1 ng g−1 for 16 foods in paper containers. No BADGE was detected in three canned foods. There was no difference in leaching concentrations of BPA into glycine buffers at pHs 8 and 11, and water. The amounts of BPA leached into water from six epoxy resin cans held at 121°C for 20 min were almost the same as the cans’ contents and were much higher than the amounts leached from cans held at or below 80°C for 60 min. The amount leached depended on the type of can, but not on the amount of BADGE leached from the cans. Considerably more BPA than BADGE leached to water from six cans. Two cans whose contents had high concentrations of BPA showed no BADGE leaching even at 121°C, suggesting the different kinds of epoxy resin can linings from others. The results imply that the main source of human exposure to BPA is food from cans with linings that contain high percentages of BPA as an additive or an unforeseen contaminant.

Concentrations of bisphenol A, bisphenol A diglycidyl ether, and their derivatives in canned foods in Japanese markets

Bisphenol A (BPA), bisphenol A diglycidyl ether (BADGE), and their derivatives in 38 canned foods sold in Japan were measured using high-performance liquid chromatography-mass spectrometry (LC-MS) and LC-tandem mass spectrometry (LC-MS/MS). BPA, BADGE, BADGE.2H 2O, BADGE.HCl.H2O, BADGE.HCl, and BADGE.2HCl were 0-235.4, 0-3.4, 0-247.2, 0.2-196.4, 0-3.0, and 0-25.7 ng/g, respectively, which did not exceed acceptable daily intake for BPA and specific migration limit for BADGEs. BADGE was degraded by 58, 100, 46, and 58% in water (pH 7), 0.01 N HCl (pH 2), 0.01 N NaCl (pH 6.8), and 0.01 N NaCl with acetic acid (pH 2.5), respectively, when it was allowed to stand at 120 degrees C for 30 min. The prominent derivatives formed were BADGE.2H 2O and BADGE.HCl.H2O, which was formed not only in BADGE with added HCl but also in that with NaCl. Acetic acid accelerated the formation of both BADGE.2H2O and BADGE.HCl.H2O in NaCl. No BPA was detected in any simulation samples started from BADGE. The results suggest that BPA and BADGE are independently leached into canned foods and that BADGE is easily changed to more stable compounds such as BADGE.2H2O and BADGE.HCl.H2O by sterilization.

Degradation of bisphenol-A (BPA) in the presence of reactive oxygen species and its acceleration by lipids and sodium chloride

In this study, (1) change in bisphenol-A (BPA) leached from polycarbonate (PC) tube to water samples at 37 degrees C, (2) effect of reactive oxygen species (ROS) produced by Fenton reaction on BPA recovery and thiobarbituric acid (TBA) value with or without generally existing environmental substances such as alcohol, lipids and NaCl, were investigated. Amounts of BPA leached from PC tube to water samples containing lipids possessing unsaturated fatty acid with high TBA values were significantly lower than the amount of BPA to water only, and addition of NaCl to lipid containing water further decreased BPA concentration. The result indicates that BPA could be degraded by lipoperoxides formed by auto-oxidation of lipid, and NaCl plays an important role in BPA degradation. In the presence of ROS, BPA recovery was the lowest in water and addition of EtOH increased in both BPA recovery and TBA value, suggesting that EtOH could play a role as scavenger of ROS on the oxidative BPA degradation. Furthermore, the higher the concentration of lipid and/or NaCl, the lower the BPA recovery and TBA value. Physiologically and environmentally important concentrations of NaCl could enhance oxidative degradation of BPA in the presence of ROS.

Inhibition of seawater on bisphenol A (BPA) degradation by Fenton reagents.

To investigate bisphenol-A (BPA) degradation in seawater using Fenton reagents, changes in the BPA recovery and in the concentration of BPA metabolite, BPA-o-quinone in the three water samples; BPA free deionizad water (control water), 3% aq. NaCl and seawater as a function of time after BPA fortification in the presence of radical oxygen species (ROS) at 20 degrees C were investigated. The BPA recoveries were lower in both 3% aq. NaCl and seawater than in the control water. The BPA recovery in aq. NaOCl decreased as a function of NaOCl concentration, indicating that BPA could be degraded by the potent radical ion (OCl-) at the concentration of above 2 microM. A BPA metabolite, BPA-o-quinone was formed in all the water samples after addition of ROS which was produced by Fenton reaction (reaction of 0.11 M H2O2 and 0.44 mM FeCl3.6H2O). These results indicated that BPA degradation could occur by an addition of ROS and further accelerated by the formation of OCl- in salt containing water samples. BPA recovery was the highest in seawater immediately after addition of Fenton reagents and the amount of BPA-o-quinone was very low, which suggests that seawater possesses an inhibitory system on BPA degradation. There was a positive correlation (p<0.01) between the fortified iron concentration and turbidity in seawater. Turbidity might be originated from iron-binding substances. Degradation threshold of BPA was observed when Fenton reaction was employed in seawater fortified with high amount of BPA. The present study suggested that iron trapping caused an inhibition on BPA degradation by Fenton reagents.

Determination of free polyunsaturated fatty acids and their oxidative metabolites by high-performance liquid chromatography (HPLC) and mass spectrometry (MS)

Abstract Most of free-polyunsaturated fatty acids (f-PUFA) and their oxidative metabolites are heat unstable and have low boiling point. Also, these metabolites have many isomers with complex structure. Gas chromatography–mass spectrometry (GC–MS) has been generally and widely used for the identification and/or determination of f-PUFA and their oxidative metabolites in seafood or biological samples. High-performance liquid chromatography–mass spectrometry (HPLC–MS), however, is more convenient and useful for the analyses of these substances, since it requires no complicated pretreatment and shows high specificity and high sensitivity

Effects of perinatal low BPA on monoamines and MAO in the brain of mice

ductive states in female rats, as an estrogen fluctuation in blood. If this is the case, the rectification index (RI), the ratio of AMPA responses at −60 mV divided to those at +40 mV, might be changed: most AMPARs contain GluR2 and their RI were almost 1.5 but GluR2-lacking AMPARs show larger RI. Importantly, AMPARs are critically involved in synaptic plasticity and GluR2lacking AMPARs play a role in the induction of the long-term potentiation (LTP), which is a cellular substrate for learning and memory. In the present study, we found that the RI in the CA1 hippocampal neurons at diestrus rats was higher than at proestrus rats only after passive avoidance conditioning procedure consisting in associating darkness with a nociceptive stimulus (electrical shock, 0.8 mA, 2 s). Since this conditioning is a preparation in studies of molecular mechanisms of hippocampal depended memory, the results suggested the induction of GluR2-lacking AMPARs for the learning performace only at diestrus but not at proestrus. Furthermore, the induction of CA1 hippocampal LTP with the 3-Hz-paired protocol was occluded only after conditioning at proestrus but not at diestrus. Without the conditioning, we successfully induced the LTP at either proestrus or diestrus. Next, we examined the Y-maze alternation task (hippocampus-dependent) after conditioning at proestrus and diestrus. The Y-maze performance was significantly impaired at proestrus but not diestrus. We concluded that the mechanism for establishment of learning is varied during the estrous cycle and this may be because of estrogen fluctuation. We confirmed that estrogen blocked the increase in the RI by conditioning and impaired the Y-maze alternation task only after conditioning, in ovariectomized rats.