Synthesis and characterization of N,N-dichlorinated amino acids: taurine, homotaurine, GABA and L-leucine.

Epilepsy, trauma and other circumstances leading to hyperexcitable conditions in the CNS tend neurochemically to be associated with excessive stimulated release of glutamic acid and/or a failure of GABA modulated inhibition. Somewhat to a lesser extent, taurine and its homologue homotaurine, have also been shown to antagonize the excitatory actions of glutamic acid. Here we report the successful synthesis and isolation in pure form of N,N-dichlorinated GABA, taurine, homotaurine and leucine. These compounds are much more lipophilic than their parent compounds and may therefore more readily penetrate the blood-brain barrier systems into the neural tissue, where they can be easily dechlorinated. Very preliminary biological testing shows that this may indeed occur. The synthesis and purification methodology will likely also be applicable to a number of other amino acids as well as certain peptides or selected proteins.

Epoxide formation from diallyl sulfone is associated with CYP2E1 inactivation in murine and human lungs.

We tested the hypothesis that an epoxide formed from diallyl sulfone (DASO(2)) is responsible for inactivation of CYP2E1 in murine and human lungs. An epoxide (1,2-epoxypropyl-3,3'-sulfonyl-1'-propene [DASO(3)]) was synthesized from DASO(2) and conjugated with glutathione (GSH) to produce the conjugates S-(1R, S-[[1-hydroxymethyl-2,3' -sulfonyl]-1' -propenyl]ethyl)glutathione (diastereomers) and S-(1-[[2R,S-hydroxypropyl]-3, 3'-sulfonyl]-1'-propenyl)glutathione (diastereomers). Analysis of these conjugates by high performance liquid chromatography revealed a major peak eluting at 20.5 min. This peak was detected in incubations of murine and human lung microsomes containing DASO(2) and nicotinamide adenine dinucleotide phosphate (NADPH), and was not detected in incubations performed in the absence of DASO(2) or NADPH. The amounts of epoxide-derived GSH conjugates formed in the incubations were concentration-dependent and achieved saturation at 0.75 mM DASO(2). Formation of the conjugates was also time-dependent and peaked at 2.0 h after DASO(2). The peak containing the GSH conjugates was also detected in incubations of CYP2E1-expressed lymphoblastoid microsomes, NADPH, and DASO(2). Maximal amounts of DASO(3), as estimated by formation of a 4-(p-nitrobenzyl)pyridine derivatized product, were detected in murine lung microsomes incubated for 35 min with 1 mM DASO(2). The derivatized DASO(3) was not detectable in incubations of human lung microsomes. p-Nitrophenol hydroxylation, a catalytic activity associated with CYP2E1, was reduced in murine and human lung microsomes incubated with DASO(2), with decreases that were concentration-dependent. Dose-dependent decreases in hydroxylase activity were also found in microsomes from mice treated in vivo with DASO(2) (25 to 200 mg/kg). These results supported the premise that an epoxide formed from DASO(2) mediates inactivation of lung CYP2E1. Furthermore, the findings suggested that the mouse model is relevant for studies of DASO(2) in human lung.

Inactivation of hepatic CYP2E1 by an epoxide of diallyl sulfone.

Diallyl sulfone (DASO(2)) inhibits hepatic CYP2E1. In this investigation, we have tested the hypothesis that an epoxide formed from DASO(2) is responsible for inactivation of hepatic CYP2E1 in mice. An epoxide of DASO(2) (1,2-epoxypropyl-3, 3'-sulfonyl-1'-propene; DASO(3)) was synthesized and conjugated to glutathione (GSH) to produce the conjugates S-(1R,S-[[ 1-hydroxymethyl-2,3'-sulfonyl]-1'-propenyl]ethyl)glutathione (diastereomers) and S-(1-[[2R,S-hydroxypropyl]-3, 3'-sulfonyl]-1'-propenyl)glutathione (diastereomers). Their identities were confirmed by (1)H NMR analysis, and these were used as analytical standards. HPLC analysis revealed a major peak for the GSH conjugates that eluted at 20.5 min. This peak was detected in liver microsomal incubations performed with DASO(2) in the presence of NADPH. A similar peak also was detected in incubations of CYP2E1-expressed lymphoblastoid microsomes, NADPH and DASO(2). The generation of the epoxide-derived GSH conjugates in the microsomal incubations was concentration-dependent, and reached saturation at 0. 75 to 1.0 mM DASO(2). Formation of the conjugates was also time-dependent and peaked at 2.0 h after DASO(2). Levels of DASO(3) formed from DASO(2), as estimated by production of a 4-(p-nitrobenzyl)pyridine derivative, were maximal at 1 mM DASO(2) at 30 min. CYP2E1-dependent p-nitrophenol hydroxylase activity was decreased in microsomes incubated with DASO(2), with alterations that were proportional to the concentration of DASO(2) (0.25-1.0 mM) used. Dose-dependent decreases in hydroxylase activity also were found in microsomes from mice treated in vivo with DASO(2) (25-200 mg/kg). These DASO(2)-induced decreases corresponded with reduced amounts of immunodetectable CYP2E1. Levels of spectrally detectable P450 and heme were both diminished by DASO(2). These results supported the contention that an epoxide formed from DASO(2) mediates the inactivation of hepatic CYP2E1.

Preparative separation of pyrrolizidine alkaloids by high-speed counter-current chromatography.

We have applied a high-speed counter-current chromatography (CCC) technique to the separation and purification of pyrrolizidine alkaloids from Amsinckia tessellata, Symphytum spp., Trichodesma incanum (Boraginaceae), and Senecio douglasii var. longilobus (Asteraceae). Alkaloidal fractions were separated in a solvent system composed of a chloroform mobile phase and 0.2 M potassium phosphate buffer, of an optimum pH, as the stationary phase. Up to 800 mg of sample could be successfully separated in a single run, with excellent resolution of alkaloids. Lycopsamine and several of its acetylated derivatives were resolved from alkaloidal fractions of Amsinckia and Symphytum. However, diastereomeric pairs such as 7-acetyl-lycopsamine and 7-acetyl-intermedine, could not be separated. The presence of diastereoisomers was determined by gas chromatography-mass spectrometry. Trichodesma contained predominantly trichodesmine, which was resolved from a small quantity of incanine. we report the electron impact mass spectrum of incanine for the first time. Resolving power of CCC was sufficient to separate the closely related alkaloids senecionine and seneciphylline from Senecio, in addition to florosenine and retrorsine, Pyrrolizidine alkaloid compositions of the four species, determined by mass spectral techniques, were consistent with literature, except for the lack of riddelliine and the presence of the otonecine-based florosenine in Senecio douglasii var. longilobus.

Neurotoxicity in conscious rats following intraventricular SNAP, a nitric oxide donor.

A solution containing S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO.-releasing compound, was microinjected in doses of 0.25-2 mumol into a lateral ventricle of conscious rats. SNAP produced dose-dependent convulsions similar to those associated with limbic stimulation, such as tonic extension of the hindlimbs and tail, and dystonia of the forepaws. At 2 mumol, SNAP evoked hyperventilation (arterial hypocapnia), arterial hyperglycemia and caused necrotic lesions of periventricular gray (e.g. lateral septal nucleus) and white matter structures. In the caudate nucleus and lateral septal nucleus ipsilateral to injection, SNAP elicited a bipolar metabolic pattern of low glucose metabolism proximal to the ventricle with higher values occurring more distally. In control studies, we proved that the residue of SNAP decomposition, N-acetylpenicillamine disulfide injected intraventricularly (2 mumol), was without physiological, behavioral, or histological effects. Ventricular pretreatment with methylene blue (2 nmol), a putative inhibitor of guanylate cyclase and superoxide generator, suppressed several of the behavioral manifestations of 1 mumol SNAP, such as the forepaw dystonia, squinting, and facial clonus, but was ineffective on the physiological and histological variables affected by the 2 mumol SNAP dose. Another NO. donor, sodium nitroprusside (2 mumol), produced fewer behavioral and cytotoxic effects over a 55-min observation period, but caused more intense and widely distributed metabolic stimulation, especially in commissural and projection white matter tracts. The results are the basis for a conscious rat model using intraventricular injection of nitrocompounds to examine the physiological, behavioral, metabolic and cytotoxic properties of NO. in the brain.

Na+/K(+)-adenosine triphosphatase activity of pulmonary arteries after intoxication with the pyrrolizidine alkaloid, monocrotaline.

Na+/K(+)-Adenosine triphosphatase-dependent activities of K(+)- return relaxation and 86Rb uptake were studied in pulmonary arteries taken from rats with pulmonary hypertension induced by monocrotaline. Rats were given monocrotaline in drinking water, 20 mg/l, for 4 or more days. Isolated arteries were placed in tissue baths and contracted with norepinephrine or 5-hydroxy-tryptamine under K(+)-free conditions. The arteries relaxed when K+ was "returned" to the bath. Compared to arteries from untreated rats, arteries taken from rats pretreated with monocrotaline developed less force in response to contracting agents and did not relax to the same extent. After 4 days treatment with monocrotaline, the rate of relaxation of the arteries in response to K(+)-return was slower than that of arteries taken from untreated rats. Endothelial trauma or in vitro treatment with ouabain produced a similar decrease in the rate of relaxation. Uptake of radiolabeled Rb by perfused arteries was not altered by 4 days of monocrotaline pretreatment. Isolated lungs taken from monocrotaline-pretreated rats (5 days of ingestion of 20 mg/l of monocrotaline drinking water) accumulated similar quantities of 86Rb+ during 40-sec perfusions. Shorter perfusion times, 10 and 20 sec, resulted in greater rates of uptake of 86Rb- by lungs taken from monocrotaline-treated rats. Monocrotaline produced changes in both the mechanical and biochemical properties of pulmonary arteries after only 4 to 5 days. These changes were associated with ouabain-sensitive processes. It appears, therefore, that one of the early targets in monocrotaline intoxication is the Na+/K+ pump of the pulmonary arteries.

Indoxyl-beta-D-glucuronide, a novel chromogenic reagent for the specific detection and enumeration of Escherichia coli in environmental samples.

About 97% of Escherichia coli strains produce beta-glucuronidase, but almost all other Enterobacteriaceae lack this enzyme. A D-glucopyranosiduronic acid (glucuronide) possessing a readily detectable beta-linked aglycone should, therefore, constitute a specific reagent for the detection of this organism. For this purpose, the title compound has been synthesized for the first time. The synthesis proceeds in eight steps from readily available D-glucuronolactone, anthranilic acid, and chloroacetic acid and can be carried out on a large scale. The compound has the predicted properties: when included in the standard membrane filter test for the analysis of water, indoxyl-beta-D-glucuronide allows specific detection of E. coli through the formation of blue colonies that are the result of rapid conversion of the liberated aglycone to indigo. The recovery of E. coli is easily measured and almost quantitative.

Synthesis of benzylpenicillin by cell-free extracts from Streptomyces clavuligerus.

Cell-free enzyme concentrates from Streptomyces clavuligerus were found to convert phenylacetyl-L-cysteinyl-D-valine (PCV) directly into benzylpenicillin when incubated under reaction conditions which support the activity of isopenicillin N synthetase. The formation of benzylpenicillin was detected both by biological assay and by high performance liquid chromatography. Supplementation of PCV-containing reaction mixtures with cofactors required for ring expansion activity did not result in the production of cephalosporins. Incubation of phenoxyacetyl-L-cysteinyl-D-valine (PoCV) under the same reaction conditions did not result in the formation of penicillin V or any cephalosporin product.

Enzymatic synthesis of the penicillin and cephalosporin nuclei from an acyclic peptide containing carboxymethylcysteine.

The tripeptide delta-(L- carboxymethylcysteinyl )-L-cysteinyl-D-valine (L-CMC-CV) is converted sequentially into the CMC analog of isopenicillin N, the CMC analog of penicillin N, and the CMC analog of desacetoxycephalosporin C by, respectively, isopenicillin N synthetase, isopenicillin N epimerase, and desacetoxycephalosporin C synthetase, all isolated from the beta-lactam producing prokaryote Streptomyces clavuligerus.

Cephalosporin formation by cell-free extracts from Streptomyces clavuligerus.

Cell-free extracts of Streptomyces clavuligerus convert delta-L-(alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) into an antibiotic product which is 30 approximately 50% penicillinase-insensitive. Thin-layer chromatography resolves this antibiotic product into one major penicillinase-sensitive component and one major and one minor penicillinase-resistant component. The major and minor penicillinase-resistant antibiotics co-chromatograph with deacetoxycephalosporin C and deacetylcephalosporin C, respectively. Ring expansion of a penicillin intermediate, as evidenced by the production of penicillinase-resistant antibiotic, shows an absolute requirement for alpha-ketoglutarate, while ATP, K+ and Mg2+ have lesser effects. Ring expansion activity is not sedimented by high speed centrifugation and is unaffected by membrane-disrupting treatments. Penicillin N and ACV (presumably via penicillin N) are the only substrates so far accepted by the ring expanding enzyme. New syntheses of penicillin N and isopenicillin N are described.