Synthesis, anti-mycobacterial, anti-trichomonas and anti-candida in vitro activities of 2-substituted-6,7-difluoro-3-methylquinoxaline 1,4-dioxides

A new series of 23 6,7-difluoro-3-methyl-2-phenylthio/phenylsulfonyl/phenylsulfinyl/benzylamino/phenylamino-quinoxaline 1,4- dioxides variously substituted in the phenyl moiety, was synthesized and submitted to in vitro evaluation for anti-mycobacterial, antitrichomonas, anti-candida, anti-mycoplasma and antibacterial activities. In anti-mycobacterial assays, several compounds resulted active (MIC90 = 2.0–4.0 μg/ml) against Mycobacterium tuberculosis H37Rv. Anti-trichomonas screening showed a generally good activity of all compounds (MBC = 0.39–25.0 μg/ml) versus Trichomonas vaginalis, in particular the derivatives 5a,d, 7a, 9 and 11c ranged 0.39–0.78 μg/ml (metronidazole MBC = 12.5 μg/ml). Results of anti-candida assays showed that derivatives 7a, 8a,d and 9 were active against several species of Candida (C. albicans, C. krusei, C. parapsilosis and C. glabrata), having MIC50 between 3.9 and 31.25 μg/ml. The latter compounds were also submitted to anti-mycoplasma assay against Mycoplasma hominis, the results obtained showed that 7a, 8a,d and 9 inhibited the growth of the mycoplasma at the concentration of 0.1 mg/ml. In antibacterial tests only a few compounds showed an MIC50 lower than 62.5 μg/ml against representative strains of Gram-positive and Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio alginolyticus and Pseudomonas aeruginosa).