Nitrogen-based tetracyclic ortho-quinones (naphtho[1'2':4.5]imidazo[1,2-a]pyridine-5,6-diones, NPDOs) and their nitro-substituted derivatives (nitro-(P)NPDOs) were obtained by condensation of substituted 2,3-dichloro-1,4-naphthoquinones with 2-amino-pyridine and -pyrimidine and nitration at an elevated temperature. The structural features of the compounds as well as their global and regional electrophilic potency were characterized by means of DFT computation. The compounds were highly reactive substrates of single- and two-electron (hydride) - transferring P-450R (CPR; EC 1.6.2.4) and NQO-1 (DTD; EC 1.6.99.2), respectively, concomitantly producing reactive oxygen species. Their catalytic efficiency defined in terms of the apparent second-order rate constant (kcat/KM (Q)) values in P-450R- and NQO-1-mediated reactions varied in the range of 3-6 × 107 M-1 s-1 and 1.6-7.4 × 108 M-1 s-1, respectively. The cytotoxic activities of the compounds on tumor cell lines followed the concentration-dependent manner exhibiting relatively high cytotoxic potency against breast cancer MCF-7, with CL50 values of 0.08-2.02 µM L-1 and lower potency against lung cancer A-549 (CL50 = 0.28-7.66 µM L-1). 3-nitro-pyrimidino-NPDO quinone was the most active compound against MCF-7 with CL50 of 0.08 ± 0.01 µM L-1 (0.02 µg mL-1)) which was followed by 3-nitro-NPDO with CL50 of 0.12 ± 0.03 µM L-1 (0.035 µg mL-1)) and 0.28 ± 0.08 µM L-1 (0.08 µg mL-1) on A-549 and MCF-7 cells, respectively, while 1- and 4-nitro-quinoidals produced the least cytotoxic effects. Tumor cells quantified by AO/EB staining showed that the cell death induced by the compounds occurs primarily through apoptosis.

The multidrug resistance of Neisseria gonorrhoeae becomes a public health problem worldwide, especially the strain H041 that showed the decrease susceptibility to ceftriaxone which is the last resort for gonorrhea treatment. Therefore, the simultaneous discovery and development of a new compound to fight this pathogen is urgently required. In this study, 8-hydroxyquinoline (8HQ) and derivatives were evaluated for their antimicrobial activities against the gonococcal pathogen using spectinomycin as the reference drug. The results showed that 8HQ derivatives gave an excellent antimicrobial potency. Particularly, the dihalogenated 8HQ (iodoquinol, clioquinol and 5,7-diCl-8HQ) exerted the high activity with MIC range of 0.08-0.15 μM, 0.10-0.20 μM and 0.28-0.56 µM, respectively, compared with the reference drug (MIC = 16 μg/mL or 48.14 μM). Moreover, these compounds were also shown to be non-cytotoxic/very high safety index. The findings reveal that these three compounds could be further developed as a new antimicrobial agent for fighting the gonorrheal disease.

Antimicrobial resistance has become a prime global concern. An ability of the microbes to produce enzymes to destroy antimicrobial drugs is one of the well-known mechanisms underlying the resistance. 8-Hydroxyquinoline (8HQ) and derivatives were reported to exert diverse biological effects such as antimicrobial, antioxidant and antineurodegenerative activities. Herein, 8HQ (1), nitroxoline (NQ, 2) and 7-Br-8HQ (3) were investigated for antimicrobial activity against Enterobacteriaceae including extended spectrum β-lactamase (ESBL)-producing and carbapenemase-producing strains as well as the effect of metal ions. These compounds (1-3) displayed the great antimicrobial activity against fifty-eight bacterial isolates of Escherichia coli, Providencia rettgeri and Klebsiella pneumoniae, in which NQ (2) exerted the highest antimicrobial activity with a MIC50 of 42.04 μM (8 µg/mL) and MBC50 of 168.28 μM (32 µg/mL). The MIC values of NQ (2) and 7-Br-8HQ (3) were significantly increased in the presence of Cu2 + and Fe3+. This finding reveals that NQ could be an effective compound to be further developed as an antimicrobial agent for combating Enterobacteriaceae infections.

In the present work we modified the procedure for isolation of naphthoquinones α-methylbutyrylshikon ( 1 ), acetylshikonin ( 2 ) and β-hydroxyisovalerylshikonin ( 3 ) from Onosma visianii Clem. We also investigated possible mechanisms of 1 , 2 and 3 as antitumor agents. Accordingly, we estimated concentrations of superoxide anion radical (O2 .-), nitrite (NO2 -) and glutathione in HCT-116 and MDA-MB-231 cell lines. Compounds 1 and 3 expressed significant prooxidative activity, while all tested compounds exhibited significant increase in nitrite levels. Also, all examined compounds significantly increased the concentration of oxidized glutathione (GSSG), suggesting significant prooxidative disbalance. The levels of reduced glutathione (GSH) were also elevated as a part of antioxidative cell response. The data indicate that induced oxidative imbalance could be one of the triggers for previously recorded decreased viability of HCT-116 and MDA-MB-231 cells exposed to tested naphthoquinone derivatives. Moreover, we examined interactions mode of compounds 1 , 2 and 3 with CT-DNA as one of the crucial targets of many molecules that express cytotoxic activity. The results obtained by UV-visible, fluorescence and molecular docking study revealed that 1 , 2 and 3 bound to CT-DNA through minor groove binding. Furthermore, the interactions between HSA and 1 , 2 and 3 were examined employing the same methods as for the CT-DNA interaction study. Based on the obtained results, it can be concluded that naphthoquinones 1 , 2 and 3 could be effectively transported by human serum albumin. As a conclusion, this study provides further insight of antitumor activity of selected naphthoquinones.

A series of sixteen acetamidosulfonamide derivatives (1-16) have been synthesized and investigated for their antioxidant (radical scavenging and superoxide dismutase (SOD)) and antimicrobial activities. Most compounds exhibited antioxidant activities in which compound 15 displayed the most potent radical scavenging and SOD activities. Quantitative structure-activity relationship (QSAR) has been studied using multiple linear regression. The constructed QSAR models displayed high correlation coefficient (Q 2 LOO-CV = 0.9708 and 0.8753 for RSA and SOD activities, respectively), but low root mean square error (RMSE LOO-CV = 0.5105 and 1.3571 for RSA and SOD activities, respectively). The structure-activity relationship showed that an ethylene group connected to pyridine ring provided significant antioxidant activities. The QSAR models give insight into the rational designed of eighty new sulfonamides with various electron donating and withdrawing groups. The top five new designed sulfonamides with nitro group are potential antioxidants to be further developed for medicinal applications.