Synthesis and Biological Evaluation of (E)-3-(Nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones

Abstract

The title (E)-(3-nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones were prepared by the Claisen- Schmidt condensation of acetylpyrazines and 2-nitro-, 3-nitro- and 4-nitrobenzaldehyde in pyridine using diethylamine as the catalyst. The compounds were bioassayed for in vitro antifungal, antimycobacterial and photosynthesis-inhibiting activity. The high potency of (E)-1-(5-tert-butylpyrazin-2-yl)-3-(4-nitrophenyl)prop-2-en-1-one againstMycobacterium tuberculosis(MIC 0.78 μg/ml) and moderate activities of several compounds againstTrichophyton mentagrophytesandCandidaspp. do not support the assumption that phenolic groups are essential for antimycobacterial and antifungal activity of chalcones and their analogues. In fact, the nitro-substituted compounds were superior to the previously described hydroxylated congeners with antimycobacterial activity (MIC ≥ 12.5 μg/ml). The compounds also reduced chlorophyll content in green algaChlorella vulgaris, and some of them inhibited photosynthetic electron transport in spinach chloroplasts as well. The photosynthesis-inhibiting activity of nitro derivatives was lower than that of the corresponding hydroxylated analogues.