Electrocatalytic Hydrogenation of Pyridines and Other Nitrogen-Containing Aromatic Compounds.

The production of cyclic amines, which are vital to the pharmaceutical industry, relies on energy-intensive thermochemical hydrogenation. Herein, we demonstrate the electrocatalytic hydrogenation of nitrogen-containing aromatic compounds, specifically pyridine, at ambient temperature and pressure via a membrane electrode assembly with an anion-exchange membrane. We synthesized piperidine using a carbon-supported rhodium catalyst, achieving a current density of 25 mA cm-2 and a current efficiency of 99% under a circular flow until 5 F mol-1. Quantitative conversion of pyridine into piperidine with 98% yield was observed after passing 9 F mol-1, corresponding to 65% of current efficiency. The reduction of Rh oxides on the catalyst surface was crucial for catalysis. The Rh(0) surface interacts moderately with piperidine, decreasing the energy required for the rate-determining desorption step. The proposed process is applicable to other nitrogen-containing aromatic compounds and could be efficiently scaled up. This method presents clear advantages over traditional high-temperature and high-pressure thermochemical catalytic processes.

Quantitative Analysis and Manipulation of Alkali Metal Cations at the Cathode Surface in Membrane Electrode Assembly Electrolyzers for CO2 Reduction Reactions.

The stable operation of the CO2 reduction reaction (CO2RR) in membrane electrode assembly (MEA) electrolyzers is known to be hindered by the accumulation of bicarbonate salt, which are derived from alkali metal cations in anolytes, on the cathode side. In this study, we conducted a quantitative evaluation of the correlation between the CO2RR activity and the transported alkali metal cations in MEA electrolyzers. As a result, although the presence of transported alkali metal cations on the cathode surface significantly contributes to the generation of C2+ compounds, the rate of K+ ion transport did not match the selectivity of C2+, suggesting that a continuous supply of high amount of K+ to the cathode surface is not required for C2+ formation. Based on these findings, we achieved a faradaic efficiency (FE) and a partial current density for C2+ of 77 % and 230 mA cm-2, respectively, even after switching the anode solution from 0.1 M KHCO3 to a dilute K+ solution (<7 mM). These values were almost identical to those when 0.1 M KHCO3 was continuously supplied. Based on this insight, we successfully improved the durability of the system against salt precipitation by intermittently supplying concentrated KHCO3, compared with the continuous supply.

Comparison of the estrogenic activities of seawater extracts from Suruga Bay, Japan, based on chemical analysis or bioassay.

The present study compared estrogenicity measured by in vitro bioassay and estrogenicity estimated by the chemical analysis of seawater from Suruga Bay, Japan. Nonylphenol, bisphenol A, estrone, 17beta-estradiol, nonhydroxy polycyclic aromatic hydrocarbons, and hydroxy polycyclic aromatic hydrocarbons, some of which show estrogenic activity, were selected as the target compounds. The yeast two-hybrid system was used to evaluate the estrogenic activities of seawater and chemicals with or without rat liver S9. Concentrations of estrogenic compounds in seawater were measured by chemical analysis using gas chromatography/ mass spectrometry. The main estrogenic compounds in seawater were estrone (< or = 9.2 ng/L), bisphenol A (< or = 1,070 ng/L), and nonylphenol (< or = 276 ng/L). The highest estrogenic activities in seawater were observed near a sewage treatment plant, but the predicted potencies based on the chemistry data were higher than those observed experimentally for the estrogenic activity in seawater. The estrogenicity measured by bioassay was raised considerably after S9 treatment; this observation was limited to the zone of freshwater immediately adjacent to the wastewater outfall.

Analysis of organotins in seawater of the Southern Ocean and Suruga Bay, Japan, by gas chromatography/inductively coupled plasma mass spectrometry.

Organotins are widespread in the world's oceans and have a detrimental effect on organisms. However, there is little information on their distribution in the Southern hemisphere. We analyzed organotins in seawater from the Southern Ocean and Suruga Bay, Japan, using gas chromatography/inductively coupled plasma mass spectrometry. Organotins were compared in two contrasting environments--one in shallow, temperate coastal waters (Suruga Bay) and the other in cold, deep waters of the far Southern Ocean. Twelve kinds of organotins were detected from Suruga Bay, with tributyltin (0.184-13.6 ng Sn/L) and total organotins (0.801-19.7 ng Sn/L). In contrast, three kinds of organotins were detected in the Southern Ocean, with total organotins (from not detected to 0.266 ng Sn/L). The ratios of degraded products of tributyltin and triphenyltin from the Southern Ocean were higher than those in Suruga Bay, suggesting that fresh input of organotins into the Southern Ocean is relatively low. The presence of butyltins in Antarctic sediments and biota has been demonstrated previously; however, the present study is the first to describe trace levels of organotins in the Southern Ocean approximately 1,000 km from Antarctica.

Evaluation of ecotoxicity and fate of methylated butyltins in sediments and seawater from Tokyo Bay, Japan.

We analyzed the fate of organotins in seawater and sediments from Tokyo Bay, Japan, by gas chromatography/inductively coupled plasma mass spectrometry. We also measured the toxicity of methylated butyltins by in vitro bioassays, the retinoid X receptor (RXR) activation method, and the marine luminescent bacterium Vibrio fischeri. Concentrations of tributyltin (TBT) and tributylmonomethyltin (TBMMT) in seawater were 0.0636 to 0.419 and 0.0050 to 0.108 ng Sn/L and in sediment were 7.51 to 17.8 and 3.67 to 6.87 ng Sn/wet weight g, respectively. Methylated butyltins did not activate RXR and were not toxic to bacteria. Tributylmonomethyltin in seawater would elute from sediment since TBMMT-to-TBT ratios showed a positive correlation (r(2) = 0.858) between sediment and deep seawater. Both methylation and debutylation of TBT seem to be major routes of decomposition of TBT in sediment. Methylation of TBT would not only cause subsequent volatilization but also decrease the toxicity of TBT species in the marine environment.

Down regulation of bisphenol A glucuronidation in carp during the winter pre-breeding season.

Environmental pollution by bisphenol A is prevalent in many rivers. The influence of bisphenol A on the reproductive organs of carp has been demonstrated to be serious, especially in the winter pre-breeding season. Although bisphenol A is detoxified as bisphenol A-glucuronide in carp organs, principally the intestine, the seasonal variation in the efficiency of the detoxification is not known. To estimate the seasonal risk of bisphenol A in carp, we investigated seasonal changes in microsomal UDP-glucuronosyltransferase activity toward bisphenol A in male-carp. Seasonal elimination efficiency of bisphenol A was also examined by organ perfusion in everted intestine. No marked seasonal differences were observed in UDP-glucuronosyltransferase activity toward 1-naphthol, but high activity toward sex steroid hormones (testosterone and estradiol) was observed in the winter pre-breeding season. Low UDP-glucuronosyltransferase activity toward bisphenol A was indicated in winter. The addition of bisphenol A into the mucosal fluid of the everted intestine resulted in excretion of bisphenol A into the mucosal side of the intestine as the metabolite, bisphenol A-glucuronide. Excretion of bisphenol A-glucuronide from carp intestine was highest in summer (proximal intestine: 13.3 nmol; middle intestine: 8.3 nmol; distal intestine: 7.9 nmol) and lowest in winter (proximal intestine: 1.0 nmol; middle intestine: 1.0 nmol; distal intestine: 0.9 nmol). These results suggest that metabolism and excretion of bisphenol A in carp hepatopancreas and intestine are impaired by down regulation of UDP-glucuronosyltransferase activity in the winter pre-breeding season.

Presence and estrogenicity of anthracene derivatives in coastal Japanese waters.

An analytical method was developed to measure levels of anthracene (ANT) and its derivative compounds 9,10-anthraquinone (ATQ) and eight hydroxy-anthraquinones (hATQs) in seawater from Tokyo Bay and Suruga Bay, Japan. The hATQs produced through photochemical reaction of ANT are known to be toxic. Seawater samples contained ANT at levels ranging from < 0.2 to 4.7 ng/L, ATQ from 3.9 to 200 ng/L, 1-hydroxyanthraquinone (1-hATQ) from < 0.9 to 5.3 ng/L, and 2-hATQ from 1.6 to 5.5 ng/L. The yeast two-hybrid system was also used to evaluate the estrogenic activity of these compounds. Estrogen agonist and antagonist tests with or without rat liver S9 were carried out. Some compounds showed estrogenic activity: The strongest (2-hydroxyanthraquinone) was of similar potency to p-nonylphenol. Concentrations of some estrogenic derivatives in the samples were higher than those of the parent ANT Polycyclic aromatic hydrocarbons (PAHs) such as ANT appear able to be transformed into toxic compounds in the environment when they are irradiated by sunlight, so it is important to monitor not only PAHs but also hydroxyl-PAH-quinones in the environment.

Evaluation of the Ishikawa cell line bioassay for the detection of estrogenic substances from sediment extracts.

This study examines the application of Ishikawa human endometrial adenocarcinoma cells to measure the estrogenic activity of fractionated extracts of sediments from Tokyo Bay, Japan. Estrogen stimulates alkaline phosphatase activity in this cell line. The results of these assays were compared with those of a yeast estrogen screen (YES) assay. The Ishikawa cell line bioassay showed higher sensitivity to 17beta-estradiol (median effective concentration [EC50], 10.7 pM) than did the YES assay (EC50, 480 pM). Fractionation of sediment extracts (all samples collected from 5 sites) showed that the nonpolar fraction was poisonous to yeast cells; the estrogenic activity of this fraction, therefore, could not be measured by YES. However, the nonpolar fraction did not kill the Ishikawa cells. The 17beta-estradiol-equivalent values of 15 extracts (3 fractions from each of 5 sediment samples) ranged from 5.7 to 697 pg/g dry weight according to the Ishikawa cell line bioassay. Chemical analysis using gas chromatography-mass spectrometry revealed that the highest concentrations of endocrine-disrupting chemicals were observed at the sampling station near the sewage treatment plant. The results support that the Ishikawa cell line bioassay is suitable for measuring the estrogenic activity of sediment samples.

Stereoselective biotransformation of limonene and limonene oxide by cyanobacterium, Synechococcus sp. PCC 7942.

The biotransformation of limonene and limonene oxide by the cyanobacterium, Synechococcus sp. PCC 7942, was investigated. (S)-(+)-Limonene was hydroxylated stereo- and regioselectively at its allylic position of the endocyclic C=C double bond by the cyanobacterial cells to its corresponding alcohol. The cells also showed the ability for the enantio- and stereoselective cleavage of the epoxide group of (1S,2R,4R)-limonene oxide to give (1S,2S,4R)-limonene-1,2-diol. The repetitive production of carveol from limonene was achieved using Ca2+-alginate-immobilized cyanobacterial cells.

Gonadal histology and serum vitellogenin levels of bigeye tuna Thunnus obesus from the Northern Pacific Ocean--absence of endocrine disruption bio-indicators.

Endocrine disrupting chemicals such as organochlorines have been detected in a large number of marine fish. Histological observation of the gonads, measurement of serum vitellogenin (VTG) level and of liver polychlorinated biphenyl (PCB) content were performed to evaluate the reproductive health and the contamination with endocrine disruptors in bigeye tuna Thunnus obesus, collected in the northern Pacific Ocean in 1999 and 2000. Abnormalities commonly found in species affected by endocrine disruptors such as the presence of oocytes in the testis or elevated serum VTG levels were not found in any of males examined. Both males and females had only small amounts of liver PCB content. The results suggest that currently there is little if any risk of organochlorine contamination or endocrine disruption of gonadal function in bigeye tuna from the northern Pacific Ocean. However, further studies are necessary to evaluate the health status of the open sea fishery resources.

Slow elimination of nonylphenol from rat intestine.

Nonylphenol, a possible endocrine disrupter, tends to persist in rat liver tissue after detoxification as a glucuronide conjugate by UDP-glucuronosyltransferase 2B1 expressed in the liver. In the intestine, however, the metabolism and dynamics of nonylphenol remain to be elucidated. The objectives of this study were to clarify the metabolism and excretion of nonylphenol having a long alkyl chain in the first barrier intestine and to estimate whether the nonylphenol alkyl chain governs the speed of excretion from intestinal tissue. Organ tissue glucuronidation activity toward alkylphenols (C2, C9) was investigated using microsomes prepared from intestinal tissue. To elucidate the elimination pathway of alkylphenols (C2, C4, C6, C9), a perfusion study was conducted on everted intestine. After oral administration (5 mg) of alkylphenols (C2, C9) to rats, gastrointestinal contents and related organ tissues (gastrointestinal tissue, liver, and kidney), blood, and urine were analyzed for alkylphenols (C2, C9) and glucuronides. The intestine showed strong glucuronidation activity toward alkylphenols (C2, C9). In everted intestinal assay, nonylphenol was glucuronidated within the intestinal wall, as was the case for other alkylphenols (C2, C4, C6), but nonylphenol-glucuronide was not excreted from intestinal tissue. Orally administered nonylphenol remained for long periods in gastrointestinal tissue as both the parent compound and glucuronide. The present study confirmed that intestinal tissue possesses an alkylphenol elimination system using UDP-glucuronosyltransferase; however, this system is impaired by the marginal transport of alkylphenol-glucuronide possessing long alkyl chain, such as nonylphenol.

In vivo visual reporter system for detection of estrogen-like substances by transgenic medaka.

Detection of endocrine disrupting chemicals, in particular, environmental estrogens with living organisms, has many advantages if compared to chemical analysis. The screening of novel pollutants with meaningful endpoints, the integration of uptake, bioconcentration, and excretion as well as the evaluation of endocrine disrupting effects with respect to toxicity require in vivo biotests for estrogen-like substances (ELSs). Critical disadvantages of whole organism biotests are their low sensitivity and the need for laborious and time-consuming work. To overcome these problems, we have developed a transgenic medaka strain harboring the green fluorescence protein (GFP) gene driven by choriogenin H gene regulatory elements. Choriogenin H is an egg envelope protein induced by estrogens in the liver. With yolk sac larvae of this strain, GFP induction in liver was observed 24 h after onset of aqueous exposure to 0.63 nM 17beta-estradiol (E2), 0.34 nM ethynylestradiol, or 14.8 nM estrone. Furthermore, concentrated sewage treatment effluent induced GFP expression. Comparison of E2 equivalents estimated by GFP-induction in transgenic medaka, a YES assay, and GC/MS showed detection limits in the same order of magnitude. These results indicated that the sensitivity of the transgenic medaka strain was sufficient for application as an alternative model in monitoring environmental water samples for ELSs.