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A series of N-, S-, and O-mononitro- and dinitrobenzyl derivatives of heterocycles was synthesized by alkylation of heterocyclic bases with the respective nitrobenzyl chlorides. Of the newly synthesized compounds, dinitrobenzylsulfanyl derivatives of 1-methyl-2-mercaptoimidazole (2c) and of 5-nitro- and 5,6-dichloro-2-mercaptobenzimidazole (8b and 8c, and 8e and 8f, respectively) showed considerable antimycobacterial activity. On a molar basis, nine of the novel compounds showed also a considerably higher antiprotozoal efficacy than metronidazole that reduced T. hominis viability to 73.5% at 8 μg/ml.

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HYDROGEN SULFIDE AS A REGULATORY MOLECULE IN PLANT CELLSS u m m a r y For a long time, hydrogen sulfide has been known as strong toxin harmful to living organisms. Recent studies have shown the beneficial effect of low doses of H 2 S on functioning of both animals and plants. It was also confirmed that H 2 S acts as a signaling molecule similar to two other well-known gasotransmitters, nitric oxide and carbon monoxide. The enzymes responsible for H 2 S generation have been identified in plant cells. These include desulfhydrases, located mainly in the cytosol, as well as sulfite reductase, present in chloroplasts, and mitochondrial β-cyanoalanine synthase. Numerous studies indicated that H 2 S level increases significantly in plant tissues in response to unfavorable environmental conditions, such as salinity, heavy metals, drought, high and low temperature, suggesting its essential role in plant adaptation to abiotic stresses. I has been proposed that the main mechanism of H 2 S action is the post-translational modification of reactive cysteine residues in proteins, called S-sulfhydration.