Synthesis of 4-aryl substituted 3,4-dihydropyrimidinones using silica-chloride under solvent free conditions

This paper describes an improved procedure for the efficient and facile synthesis of 4-aryl substituted 3, 4-dihydropyrimidinones under mild reaction conditions with excellent yields using inexpensive silica chloride under solvent free conditions.

A simple and economical chemical neutralization method for the destruction of sulfur mustard and its analogues

A simple and economical chemical neutralization method is developed against highly toxic chemical warfare agent's viz. sulfur mustard (SM), sesquimustard, and their homologues/analogous. The method involves treatment of chemical warfare agents with sodium in inert solvents. This destruction method of sulfur mustards release innocuous products via desulfurization reactions. The products were characterized by GC-MS technique. The method is suitable in particular, for bulk destruction of heel of mustard stockpiles.

Protective effect of ethanolic and water extracts of sea buckthorn (Hippophae rhamnoides L.) against the toxic effects of mustard gas

Ethanolic extract of H. rhamnoides L. leaf (HL-EOH), water and ethanolic extract of H. rhamnoides fruit (HF-W and HF-EOH), and H. rhamnoides flavone from fruit (HR-flavone) were evaluated against percutaneously administered sulphur mustard (SM), a chemical warfare agent. The animals administered with SM (9.7, 19.3 and 38.7 mg/kg) died at various days depending upon the dose and there was a significant reduction in the body weight. The H. rhamnoides extracts (1 g/kg; 3 doses; po) significantly protected the lethality, with a protective index of 2.4, 1.7, 1.7 and 2.2 for HL-EOH, HF-W, HF-EOH and HR-flavone respectively. Reduced glutathione (GSH) and oxidized glutalthione (GSSG) levels were reduced, and malondialdehyde (MDA) was elevated after percutaneous administration of SM. Oral administration of HL-EOH and HR-flavone significantly protected the body weight loss. Recovery in the levels of GSH, GSSG and MDA were also observed following oral administration of HL-EOH and HR-flavone. All the extracts were non-toxic and the LD50 was more than 5 g/kg. The present study shows that percutaneous administration of SM induces oxidative stress and ethanolic extract of leaf of H. rhamnoides and H. rhamnoides flavone from fruit can significantly protect it.

Acute toxicity and cardio-respiratory effects of 2-deoxy-D-glucose: a promising radio sensitiser

OBJECTIVE

To evaluate the acute toxicity of 2-deoxy-D-glucose (2DG) by oral (p.o.) and intravenous (i.v.) routes, and also the cardio-respiratory effects following high doses of 2DG in animal models.

METHODS

The LD50 of 2DG (in water) was determined in rats and mice by p.o. route and in mice by i.v. route. The effect of 2-DG (250 mg/kg, 500 mg/kg, and 1000 mg/kg, i.v.) was studied on various cardio-respiratory parameters viz., mean arterial blood pressure, heart rate and respiratory rate in anaesthetised rats. The effect of 2DG (500 mg/kg, 1000 mg/kg, and 2000 mg/kg, p.o.) was also studied on various respiratory parameters viz., respiratory rate and tidal volume in conscious rats and mice using a computer program.

RESULTS

The p.o. LD50 of 2DG was found to be >8000 mg/kg in mice and rats, and at this dose no death was observed. The LD50 in mice by i.v. route was found to be 8000 mg/kg. At this dose 2 out of 4 mice died and the death occurred within 6 h. A significant increase in the body weight was observed after p.o. administration of 2DG in rats at 500 mg/kg, 1000 mg/kg, and 2000 mg/kg doses. There was no significant change in the body weight at 4000 mg/kg and 8000 mg/kg by the p.o. route in rats and up to 8000 mg/kg by p.o. as well as i.v. routes in mice. Intravenous administration of 2DG (250 mg/kg, 500 mg/kg, and 1000 mg/kg) in anaesthetised rats showed a time-dependent decrease in the mean arterial blood pressure. There was no change in the heart rate in any of the treatment groups. The tidal volume was not changed significantly by p.o administration in conscious rats, but a significant decrease in the respiratory frequency at 500 mg/kg and 1000 mg/kg doses was observed. In the mice also there was no change in the tidal volume after p.o, administration, but the respiratory frequency decreased significantly at 2000 mg/kg dose.

CONCLUSION

2DG is a safe compound but can cause a fall in the blood pressure and a decrease in respiratory frequency at high doses.

Design, synthesis and biological evaluation of novel bicyclic β-lactams as potential antimalarials

A series of bicyclic N-substituted and unsubstituted beta-lactams were synthesized and evaluated as targeted potential antimalarials. The compounds MNR4 and MNR5 were found to have highest potency against Plasmodium falciparum in vitro.

Mechanism of cardiotoxicity induced by a marine toxin isolated from Ptychodiscus brevis

An organophosphate toxin of marine origin isolated from red tide dinoflagellate P. brevis produced a dose-dependent dual effect on rat atria, i.e. positive inotropic effect at low concentrations (2.8 x 10(-8) to 8.4 x 10(-7) M) and negative inotropic and chronotropic responses at an elevated dose (4.8 x 10(-6) to 7.2 x 10(-4) M). The negative chronotropic and inotropic responses of the toxin were potentiated with physostigmine and ouabain whereas antagonized by atropine and hemicholinium-3 pretreatments and those effects remained unaltered by isoproterenol, phenylephrine and ouabain pretreatments. The results indicate that the toxin induced negative inotropic and chronotropic effects are mediated through release of acetylcholine from the nerve endings and consequent activation of muscarinic receptor. In atria exposed to guanethidine, bretylium, propranolol and tyramine tachyphylaxis, the positive inotropic response of the toxin was not modified. However, the response was antagonized by EGTA, nifedipine, ryanodine, calcium-free ringer and potentiated with caffeine and amiloride pretreatments. The results suggest that the positive inotropic effect of the toxin is mediated through Ca2+ influx and impairment of Na+/Ca2+ exchange process.

Cardiovascular effects of an organophosphate toxin isolated from Ptychodiscus brevis

The dose-dependent hypotensive and bradycardic effects induced by an ichthyotoxic organophosphate compound isolated from the marine dinoflagellate Ptychodiscus brevis were studied. These effects were not antagonized by atropine, but potentiated by alpha-adrenoceptor blocker and hexamethonium. The toxin abolished the vasopressor effect elicited by phenylephrine, indicating an alpha-adrenergic blocking activity. The cardiovascular depressor responses were antagonized by tetraethylammonium while blockade of cholinergic and histaminergic receptors or inhibition of prostaglandin synthesis failed to modify these effects. The results indicate that the cardiovascular depressor effects of the toxin are probably mediated through alpha-adrenergic and ganglionic blockade accompanied by modulation of potassium channel activity.

Acute toxicity of synthetic Gymnodinium breve toxin metabolite and its analogues in mice

Acute toxicity of synthetic Gymnodinium breve toxin metabolite and its analogues has been investigated in mice. The anticholinesterase potencies of the toxin metabolite and its analogues were determined in vitro as well as in vivo. The intraperitoneal LD50 of the parent metabolite O,O-dipropyl(E)-2-(1-methyl-2-oxopropylidene) phosphorohydrazidothioate(E)oxime in mice was higher compared to LD50 values of its analogues. The in vitro acetylcholinesterase (AChE)-inhibiting potency values were higher for diethoxy(P = O) analogue than for diispropoxy(P = O) analogue. Lethal doses of parent metabolite and its analogues significantly inhibited AChE activity in the blood and brain of mice 1 hr postexposure. The maximum inhibition by the parent metabolite was observed in both tissues. The percentage inhibition of AChE activity was greater in the blood than in the brain. The results indicate that these agents have anticholinesterase action specifically in the blood. In conclusion, the parent toxin metabolite is a more potent inhibitor of AChE in vivo, whereas higher toxicity is associated with other analogues, suggesting the involvement of other factors influencing the toxicity, which needs to be further investigated.

Monitoring of haemoglobin-methyl isocyanate adduct by high-performance liquid chromatography with diode array detector

Carbamylation of haemoglobin by methyl isocyanate (MIC) was detected by high-performance liquid chromatography (HPLC) using a photodiode array detector following cyclisation of the N-terminal valine into methyl isopropyl hydantoin (MIH). MIH was also synthesised by reaction of MIC with valine, the chromatographic conditions standardised and the spectrum derived by a photodiode array detector recorded for confirmation of the identity of MIH. This HPLC method is specific, sensitive and suitable for the detection of exposure of blood samples to methyl isocyanate.

Gas chromatographic studies of the carbamylation of haemoglobin by methyl isocyanate in rats and rabbits

Carbamylation of the N-terminal valine of haemoglobin with methyl isocyanate in rats and rabbits has been demonstrated in vitro and in vivo by gas chromatography. N-Methylcarbamylated haemoglobin, converted by cyclization into 3-methyl-5-isopropylhydantoin, has been quantified by gas chromatography. Standard hydantoin was synthesized, chemically characterized and used for calibration. The method is simple and reliable in the concentration range 0.06-2 nmol. Carbamylation of haemoglobin by methyl isocyanate in vivo in rats can be identified only above a dose of 1.05 mg/l in inhalation exposures. It is inferred that methyl isocyanate in the "active" form crosses the alveolar and erythrocyte membranes and carbamylates the haemoglobin.