Showing papers on "Brucine published in 2001"

Enzymatic and non-enzymatic reduction of brucine N -oxide by aldehyde oxidase and catalase

Abstract: 1. Brucine N -oxide was reduced by aldehyde oxidase in rabbit liver cytosol in the presence of an electron donor, 2-hydroxypyrimidine, under anaerobic conditions. The flavoprotein purified from rabbit liver exhibited significant reductase activity in the presence of electron donors. 2. Brucine N -oxide was also reduced by rabbit liver cytosol and blood in the presence of both a reduced pyridine nucleotide and FAD under anaerobic conditions. The N -oxide reductase activities were inhibited by carbon monoxide and air. However, these activities were not abolished when liver cytosol and blood were boiled. Rabbit erythrocytes exhibited the reductase activity, but not plasma. 3. When liver cytosol or blood was separated by DEAE-cellulose column chromatography, the fractions with the reducing activity in the presence of both NADH and FAD also showed catalase activity. 4. Catalase catalysed the brucine N -oxide reduction in the presence of both NAD(P)H and FAD. Hematin also exhibited the reductase activity in the...

Interactions between allosteric modulators and 4-DAMP and other antagonists at muscarinic receptors: potential significance of the distance between the N and carboxyl C atoms in the molecules of antagonists.

Abstract: Allosteric enhancement of the affinity of muscarinic receptors for their ligands offers a new way to influence cholinergic neurotransmission. The structure of the allosteric binding domain(s) and the features of agonists, antagonists and modulators which determine the occurrence of either positive or negative cooperativity require clarification. We tested interactions between allosteric modulators alcuronium, strychnine and brucine and eight antagonists at muscarinic receptors expressed in CHO cells. In experiments with unlabeled antagonists, all three modulators enhanced the affinity for 4-diphenylacetoxy-N-dimethylpiperidinium (4-DAMP) at the M2 receptors, and strychnine did so also at the M4 receptors. Positive interactions were also observed between alcuronium and L-hyoscyamine (M2) and scopolamine (M2), between strychnine and butylscopolamine (M4), L-hyoscyamine (M2 and M4) and scopolamine (M4), and between brucine and scopolamine (M2). Positive effects of alcuronium, strychnine and brucine on the affinity of the M2 receptors for 4-DAMP have been confirmed by direct measurements of the binding of [3H]-4-DAMP. A comparison of molecular models of several antagonists which are esters revealed that antagonists in which the distance between the N and the carboxyl C atoms corresponds to five chemical bonds are more likely to display positive cooperativity with alcuronium at the M2 receptors than the antagonists in which the N-carboxyl C distance corresponds to four chemical bonds.

Identification of Strychnine,Brucine and Their Metabolites in Body Fluids by Liquid Chromatography-Electrospray Ion Trap Mass Spectrometry

Abstract: Objective:A specific,sensitive and rapid LC/MS\+n method was developed for detection of strychnine,brucine and their major metabolites in blood and urine.Methods:The experiments were carried out on the electrospray ion trap mass spectrometer(Finnigan LCQ),which operated in the positive modes and several scan mode including full scan MS and full scan MS\+n.Blood samples extracted with organic solvent and urine samples eluted from SPE column were injected into ODS column and eluted with a mobile phase of 20% acetonitrile and 80% water for LC/MS analysis.Results:Blood and urine samples from a man suspected of taking Semen Strychni(ma qian zi)were analyzed and demonstrated the presence of strychnine and brucine.The detection limit was 5 ng(on column).Meanwhile,it was deduced that glucuronide conjugate was the major metabolite of strychnine in human based on the clromatography and MS data.Conclusion:It is proved that this method is especially suitable for the detection of strychnine alkaloids in body fluids of forensical and clinically toxicological relevant cases.