Synthesis and antibacterial activity of novel 11-[3-[(arylcarbamoyl)oxy]propylamino]-11-deoxy-6-O-methyl-3-oxoerythromycin A 11-N,12-O-cyclic carbamate derivatives

Synthesis and structure-activity relationships of novel 14-membered 2-fluoro ketolides with structural modification at the C11 position

A series of novel C11 substituted 14-membered 2-fluoro ketolides were synthesized and evaluated for their antibacterial activity against erythromycin-resistant and erythromycin-susceptible clinical isolates and strains from ATCC. The overall antibacterial spectra of the semi-synthetic antibiotics are similar to that of telithromycin (TEL) and most of them exhibited excellent activity against Gram-positive bacteria (S. epidermidis, S. pneumoniae, S. aureus) and several Gram-negative bacteria (M. catarrhalis, H. influenza). Compounds 11c, 11g, 11h, 11q, 12a, 12b, 12d and 12e displayed 4-16 fold more potency than TEL against all the tested erythromycin-resistant S. epidermidis strains and S. pneumonia SPN19-8 and SPN19-8. Compounds 11b, 11c, 11e, 11g, 11h, 11q, 12a, 12b and 12c showed at least 8 fold potency than TEL against erythromycin-resistant M. catarrhalis BCA19-5 and BCA19-6. Molecular docking suggested compound 12d oriented the macrolide ring and side chain similarly to solithromycin (SOL). Noticeably an additional hydrogen bond was observed between the Lys90 residue of ribosome protein L22 and the carbamate group at the C11 position, which might provide a rational explanation for the enhanced antibacterial activity of target compounds. Therefore this research would offer a new perspective for further structural optimization of the C11 side chain. Based on the results of antibacterial activity, cytotoxicity and structural diversity, 5 compounds (11a, 11b, 11h, 12d and 12i) were selected for the stability testing of human liver microsomes and compound 11a exhibited preferable metabolic stability.

New proapoptotic chemotherapeutic agents based on the quinolone-3-carboxamide scaffold acting by VEGFR-2 inhibition

In the current study, we designed and synthesized a series of new quinoline derivatives 10a-p as antiproliferative agents targeting cancer through inhibition of VEGFR-2. Preliminary molecular docking to assess the interactions of the designed derivatives with the binding site of VEGFR-2 (PDB code: 4ASD) displayed binding poses and interactions comparable to sorafenib. The synthesized compounds exhibited VEGFR-2 inhibitory activity with IC50 ranging from 36 nM to 2.23 μM compared to sorafenib (IC50 = 45 nM), where derivative 10i was the most potent. Additionally, the synthesized derivatives were evaluated in vitro for their cytotoxic activity against HepG2 cancer cell line. Seven compounds 10a, 10c, 10d, 10e, 10i, 10n and 10o (IC50 = 4.60, 4.14, 1.07, 0.88, 1.60, 2.88 and 2.76 μM respectively) displayed better antiproliferative activity than sorafenib (IC50 = 8.38 μM). Compound 10i was tested against Transformed Human Liver Epithelial-2 normal cell line (THLE-2) to evaluate its selective cytotoxicity. Furthermore, 10i, as a potent representative of the series, was assayed for its apoptotic activity and cell cycle kinetics' influence on HepG2, its effects on the gene expression of VEGFR-2, and protein expression of the apoptotic markers Caspase-7 and Bax. Compound 10i proved to have a potential role in apoptosis by causing significant increase in the early and late apoptotic quartiles, a remarkable activity in elevating the relative protein expression of Bax and Caspase-7 and a significant reduction of VEGFR-2 gene expression. Collectively, the obtained results indicate that compound 10i has a promising potential as a lead compound for the development of new anticancer agents.

The search for novel treatment strategies for Streptococcus pneumoniae infections

This review provides an overview of the most important novel treatment strategies against Streptococcus pneumoniae infections published over the past 10 years. The pneumococcus causes the majority of community-acquired bacterial pneumonia cases, and it is one of the prime pathogens in bacterial meningitis. Over the last 10 years, extensive research has been conducted to prevent severe pneumococcal infections, with a major focus on (i) boosting the host immune system and (ii) discovering novel antibacterials. Boosting the immune system can be done in two ways, either by actively modulating host immunity, mostly through administration of selective antibodies, or by interfering with pneumococcal virulence factors, thereby supporting the host immune system to effectively overcome an infection. While several of such experimental therapies are promising, few have evolved to clinical trials. The discovery of novel antibacterials is hampered by the high research and development costs versus the relatively low revenues for the pharmaceutical industry. Nevertheless, novel enzymatic assays and target-based drug design, allow the identification of targets and the development of novel molecules to effectively treat this life-threatening pathogen.

In vitro evaluation of new 2-phenoxy-benzo[g][1,2,4]triazolo[1,5-a]quinazoline derivatives as antimicrobial agents

Previously, seventeen 2-phenoxy-benzo[g][1,2,4]triazolo[1,5-a]quinazoline derivatives were prepared and characterized by physicochemical and spectral means. This study was conducted to evaluate their activities in vitro against five Gram-negative and five Gram-positive of clinically pathogenic bacterial strains and ten fungal strains. The antimicrobial activity was assessed, and the minimum inhibitory concentration values of the tested compounds were determined in μg ml^-1, using the diffusion agar technique. The bacterial strains used were Escherichia coli (ATCC 25922), Proteus mirabilis (ATCC 7002), Klebsiella oxytoca (ATCC 700324), Pseudomonas aeruginosa (ATCC 10145), Enterobacter cloacae (ATCC 13047D-5), Bacillus subtilis (NRRL B-543), Enterococcus faecalis (RCMB 0100154-2), Staphylococcus aureus (ATCC 29213), Staphylococcus epidermidis (ATCC 12228), and Streptococcus pyogenes (RCMB 0100174-2). Aspergillus fumigatus (RCMB 02568), Syncephalastrum racemosum (IMI 21178), Geotricum candidum (IMI 329542), Candida albicans (ATCC 10231), Aspergillus niger (IMI 130783), Cryptococcus neoformans (NRRL Y-1518), Candida tropicalis (RCMB 05239), Penicillium expansum (IMI 146655), Microsporum canis (RCMB 0834), and Trichophyton mentagrophytes (RCMB 0925) were used as the fungal strains. Ampicillin and gentamicin were used as reference antibacterial drugs and amphotericin B was used as the reference antifungal drug. The antimicrobial studies revealed that the tested compounds 6-8, 11, 12, and 14-16 showed the highest activities against the bacterial and fungal strains. The current study showed that some benzo[g]traizoloquinazolines displayed remarkable antimicrobial activity and could be used as template for further design of potent antimicrobial agent.