Abstract:The condensation of substituted pyrazine-2-carboxylic acid chlorides with ringsubstituted anilines yielded five substituted pyrazine-2-carboxylic acid amides. The synthesis, and analytical, lipophilicity and biological data of the newly synthesized compounds are presented in this paper. The photosynthesis inhibition, antialgal activity and the effect of a series of pyrazine derivatives as abiotic elicitors on the accumulation of flavonoids in a callus culture of Ononis arvensis (L.) were investigated. The most active inhibitor of the oxygen evolution rate in spinach chloroplasts was 6-chloro-pyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2, IC 50 = 51.0 μmol·L -1 ). The highest reduction of chlorophyll content in Chlorella vulgaris was found for 5-tert-butyl-N-(4-chloro-3-methylphenyl)-pyrazine-2-carboxamide (3, IC 50 = 44.0 μmol·L -1 ). The maximal flavonoid production (about 900%) was reached after a twelve-hour elicitation process with 6-chloropyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2).

The condensation of chlorides of substituted pyrazinecarboxylic acids with ring-substituted anilines yielded twelve substituted pyrazinecarboxylic acid amides. The synthetic approach, analytical, and lipophilicity data of the newly synthesized compounds are presented. Two antituberculosis assays were used. Firstly, the antimycobacterial activity against four different Mycobacterium strains in a series of pyrazine derivatives was investigated. Secondly, the antimycobacterial evaluation was performed at the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) program. Interesting in vitro antimycobacterial activity was found, N-(3-iodo-4-methyl-phenyl)pyrazine-2-carboxamide (9) was most active derivative compound against M. tuberculosis (MIC < 2.0 μmol/L), while another iodo derivative 5-tert-butyl-6-chloro-N-(3-iodo-4-methyl-phenyl)pyrazine-2-carboxamide (12) was the most active compound in the TAACF antituberculosis screening program (IC90 = 0.819 µg/mL).