Enzyme inhibition and antibacterial potential of 4-Hydroxycoumarin derivatives

The 4-Hydroxycoumarin derivatives are known to show a broad spectrum of pharmacological applications. In this paper we are reporting the synthesis of a new series of 4-Hydroxycoumarin derivatives synthesized through Knovenegal condensation; they were characterized by using UV-Vis, FT-IR, NMR spectroscopies. The synthesized compounds were evaluated for antibacterial activity against Staphylococcus aureus and Salmonella typhimurium strains. The compounds (2), (3) and (8) showed favorable antibacterial activity with zone of inhibitions 26.5± 0.84, 26.0 ± 0.56 and 26.0 ± 0.26 against Staphylococcus aureus (Gram-positive) respectively. However, the compounds (5) and (9) were found more active with 19.5 ± 0.59 and 19.5 ± 0.32 zone of inhibitions against Salmonella typhimurium (Gram-negative). Whereas, in urease inhibition assay, none of the synthesized derivatives showed significant anti-urease activity; although, in carbonic anhydrase-II inhibition assay, the compound (2) and (6) showed enzyme inhibition activity with IC50 values 263±0.3 and 456±0.1, respectively.

Visualization of Proteus mirabilis within the matrix of urease-induced bladder stones during experimental urinary tract infection.

The virulence of a urease-negative mutant of uropathogenic Proteus mirabilis and its wild-type parent strain was assessed by using a CBA mouse model of catheterized urinary tract infection. Overall, catheterized mice were significantly more susceptible than uncatheterized mice to infection by wild-type P. mirabilis. At a high inoculum, the urease-negative mutant successfully colonized bladders of catheterized mice but did not cause urolithiasis and was still severely attenuated in its ability to ascend to kidneys. Using confocal laser scanning microscopy and scanning electron microscopy, we demonstrated the presence of P. mirabilis within the urease-induced stone matrix. Alizarin red S staining was used to detect calcium-containing deposits in bladder and kidney tissues of P. mirabilis-infected mice.

Immunogenicity and safety of recombinant Helicobacter pylori urease in a nonhuman primate.

Groups of squirrel monkeys (Saimiri spp.), predetermined to be free of Helicobacter infections in the gastric mucosa, were immunized orally with 0.5-4.5 mg of Helicobacter pylori recombinant urease (rUrease) and 25-500 micrograms of Escherichia coli heat-labile enterotoxin (LT) adjuvant. Oral immunization with rUrease resulted in a markedly elevated serum immunoglobulin G (IgG) antibody response with peak levels at 45 days after immunization. No significant gastric inflammation or cytotoxicity was evident in rUrease immunized monkeys as determined by light and electron microscopy. Twenty-five micrograms of LT was a sufficient and safe adjuvant dosage, whereas higher dosages resulted in diarrhea and lethargy. Animals developed a serum IgG antibody response to LT that did not impede the production of anti-rUrease antibody levels. The results of this investigation indicate that rUrease is immunogenic in a nonhuman primate.

[The effects of biotin on the metabolism of ammonia and amino acids in urease-induced hyperammonemic rats].

The effects of oral and intraperitoneal administration of biotin in urease-induced hyperammonemic rats, as well as the influence of biotin deficiency, have been studied. Biotin deficiency was produced by feeding standard diet MF (Oriental Yeast Co.) supplemented with dry egg-white (egg-white group). Egg-white + biotin group had free access to 0.0014% of biotin solution at all time. Following an intraperitoneal injection of urease, 25 U/kg (B.W.), plasma ammonia levels in egg-white + biotin group were lower than in egg-white group, especially there was significance (p less than 0.05) at 8 hours after the urease injection. Similarly, plasma ammonia levels in biotin-injected rats, in which 1 mg of biotin had been injected intraperitoneally prior to the experiment, were significantly low compared with saline-injected controls at 4 and 6 hours after urease administration. Results of plasma amino acid analysis, 9 hours after the urease injection indicated that Fischer's molar ratio (Leu + Ileu + Val/Tyr + Phe) was significantly higher in the biotin-injected rats than the saline-injected control. It suggests that biotin might decrease blood ammonia by facilitating the detoxification mechanism as follow: L-glutamate + NH3----L-glutamine.