Characterization of cytoprotective and toxic properties of iron chelator SIH, prochelator BSIH and their degradation products.

Free cellular iron catalyzes the formation of toxic hydroxyl radicals and therefore chelation of iron could be a promising therapeutic approach in pathological states associated with oxidative stress. Salicylaldehyde isonicotinoyl hydrazone (SIH) is a strong intracellular iron chelator with well documented potential to protect against oxidative damage both in vitro and in vivo. Due to the short biological half-life of SIH and risk of toxicity due to iron depletion, boronate prochelator BSIH has been designed. BSIH cannot bind iron until it is activated by certain reactive oxygen species to active chelator SIH. The aim of this study was to examine the toxicity and cytoprotective potential of BSIH, SIH, and their decomposition products against hydrogen peroxide-induced injury of H9c2 cardiomyoblast cells. Using HPLC, we observed that salicylaldehyde was the main decomposition products of SIH and BSIH, although a small amount of salicylic acid was also detected. In the case of BSIH, the concentration of formed salicylaldehyde consistently exceeded that of SIH. Isoniazid and salicylic acid were not toxic nor did they provide any antioxidant protective effect in H9c2 cells. In contrast, salicylaldehyde was able to chelate intracellular iron and significantly preserve cellular viability and mitochondrial inner membrane potential induced by hydrogen peroxide. However it was consistently less effective than SIH. The inherent toxicities of salicylaldehyde and SIH were similar. Hence, although SIH - the active chelating agent formed following the BSIH activation - undergoes rapid hydrolysis, its principal decomposition product salicylaldehyde accounts markedly for both cytoprotective and toxic properties.

New Antimycobacterial Leads from Multicomponent Hydrazino-Ugi Reaction.

BACKGROUND: Previously, modification of isoniazide- and pyrazinamide-derived pharmacophores via the Ugi multicomponent reaction proved to be an effective strategy to obtain efficacious and non-cytotoxic antimycobacterial leads. OBJECTIVE: To apply the hydrazino-Ugi reaction developed in our group toward modifying these pharmacophores with similar appendages as reported previously; to create hydrolytically more stable compounds which are based on acyl hydrazine, rather than diamide backbone. METHOD: Six hydrazino-Ugi products were synthesized and modified at the reactive nitrogen atom via reductive alkylation. Additionally, by conducting the hydrazino-Ugi reaction in methanol, three methyl ester by-products were obtained and tested alongside the main library. Compounds were screened against M. tuberculosis H37Rv strain and checked for cytotoxicity vs. HEK293 cells. Hydrolytic stability of a model Ugi and one of the newly synthesized hydrazino-Ugi products was compared in rat plasma stability experiments. RESULTS: 6 out of 20 compounds prepared and tested, displayed potent inhibition of M. tuberculosis growth and virtually no cytotoxicity in the testing concentration range. The stability of a sample hydrazino-Ugi product in rat plasma was over 3 times higher compared to that of one of the Ugi products reported earlier. CONCLUSION: Hydrazino-Ugi reaction represents an effective way to modify classical antitubercular chemotypes and generate compounds endowed with specific antimycobacterial activity. These are new, hydrolytically stable leads for the future antitubercular therapy development.

Potential of a novel antibiotic, 2-methylheptyl isonicotinate, as a biocontrol agent against fusarial wilt of crucifers.

Screening for newer bioactive compounds from microbial metabolites resulted in the isolation of a novel antibiotic from the culture filtrate, Streptomyces sp 201, of a soil. The bioactive compound, with antifungal and antibacterial activity, was identified as 2-methylheptyl isonicotinate. The antifungal activity of live culture, culture broth and the isolated bioactive compound showed marked inhibition against dominant soil-borne phytopathogens such as Fusarium oxysporum Schlect, F moniliforme Sheldon, F semitectum Berkeley & Ravenel, F solani (Martius) Sacc and Rhizoctonia solani Kuehn. The compound had no effect on seed germination and seedling development as displayed by root and stem growth of the test plant species. In pot experiments with seedlings of cruciferous plants such as Raphanus sativus L (radish), Brassica campestris L (yellow mustard), Brassica oleracea var botrytis L (cauliflower), the antibiotic compound showed promising protective activity of 92% when seeds of the test plants were treated at a dose of 50 micrograms ml-1 prior to sowing. Seed treatment with a spore suspension (3 x 10(8) spores ml-1) of the Streptomyces sp 201 displayed protective activity in the range of 56-60%. Seeds coated with 2.5% methyl cellulose-amended spores of the antagonist showed protective activity in the range of 64-72%. Further, seed treatment with the culture filtrate of the antagonist also showed promising protective activity in the range of 64-84%.

[The neurotropic and cardiotropic properties of new amino acid derivatives of isonicotinic acid]. / Neirotropnye i kardiotropnye svoistva nekotorykh novykh aminokislotnykh proizvodnykh izonikotinovoi kisloty.

Different derivatives of isonicotinic acid are used widely enough as antimicrobial and antituberculous agents. However, their neurotropic and cardiotropic effects have been studied little. The paper is concerned with investigations of these types of the activity of the new derivatives of isonicotinic acid: beta-phenyl-beta-alanine, l-proline, DL-valine, beta-alanine and DL-threonine synthesized for the first time at the Institute of Fine Organic Chemistry, Academy of Sciences of Armenia.

Drug-induced hepatic microgranulomatosis in cynomolgus monkeys.

This report discusses a unique drug-induced hepatotoxicity in cynomolgus monkeys treated orally with a novel potassium sparing experimental diuretic, [2,6-bis(4-chlorophenyl)-4-pyridinecarboxylic acid]. Groups of 6 adult male and female monkeys were treated orally with vehicle diluent, modified vehicle #122 or a suspension of the drug at 5.0, 12.5, or 32.0 mg/kg/day for 2 weeks. Another group of 5 monkeys were treated orally with 25.0 mg/kg/day of the drug for 2 weeks. Disposition of the drugs was evaluated in 2 monkeys in the later group that received 27.4 mg/kg of radiolabelled drug on the 1st and last day of dosing. Hepatic toxicity was characterized biochemically, light and electron microscopically, histochemically, immunocytochemically, and toxico-kinetically. Conjugated serum bilirubin, alanine transaminase, and aspartate transaminase levels were increased in monkeys treated with over 12.5 mg/kg/day of the diuretic. The periacinar hepatic plates of monkeys treated with 25.0 or 32.0 mg/kg/day were distorted by accumulation of PAS and oil red-O positive multinucleated Kupffer cells. The cytosol of these cells was expanded by phagolysosomes containing granular materials of varying electron densities. Granular electron dense materials were also in endothelial cells and bile canaliculi. Fatty change, cholestasis, and rare piecemeal hepatic necrosis were minimal. The drug was primarily excreted through urine. Plasma concentration and half life of the drug were increased with multiple dosing. The highest concentration of unexcreted parent drug was in the liver. Drug-induced noninflammatory hepatic microgranulomatosis, apparently caused by sequestered drug-lipid/mucopolysaccharide complex in the phagocytic cells of the liver, can occur in any species, including humans, if orally administered xenobiotics are presented to the liver in particulate form.

Analysis of the mechanism of isoniazid-induced developmental toxicity with frog embryo teratogenesis assay: Xenopus (FETAX).

The developmental toxicity of isoniazid (INH) and the metabolites acetylhydrazide (AH) and isonicotinic acid (INA) were examined with the frog embryo teratogenesis assay-Xenopus (FETAX). Late Xenopus laevis blastulae were exposed to INH, AH, and INA for 96 h in two separate static-renewal tests with and without the presence of three differently induced metabolic activation systems (MAS). The MAS consisted of uninduced, Aroclor 1254-induced, and INH-induced rat liver microsomes. Addition of the INH-induced MAS decreased the 96 h LC50 of INH and AH approximately 1.6-fold and 7.9-fold, respectively. The 96 h EC50 (malformation) of INH was virtually unaffected; however, the INH-MAS decreased the teratogenic index (TI) [96 h LC50/96 h EC50 (malformation)] nearly 1.8-fold. The 96 h EC50 (malformation) of AH increased approximately 2.0-fold, decreasing the teratogenic index value 15.8-fold. INA yielded a teratogenic index value of 2.5. Neither the uninduced MAS nor the Aroclor 1254-induced MAS had an effect on any of the compounds tested and none of the MAS affected the developmental toxicity of INA. Results from this study suggest that mixed functional oxidase metabolism may alter the developmental toxicity of INH in vitro by producing a more embryolethal, but less teratogenic metabolite(s) than INH or AH themselves. Results are indicative of the utility and versatility of FETAX in evaluating toxicological mechanisms of teratogenesis in vitro.

[Pharmaco-toxocologic study of the anti-tuberculosis preparation prothionimide]. / Farmako-toksikologicheskoe izuchenie protivotuberkuleznogo preparata protionamida

Investigations of prothionamide effected on different animal species showed the drug to be of low toxicity. In relatively big doses it produced adynamia, hypothermy and a fall of arterial pressure. When employed in doses much higher (by 10-20 times) than therapeutic ones for humans prothionamide, when used repeatedly, may exercise a hepatotoxic action.