A novel bis(pyrazolyl)methane compound as a potential agent against Gram-positive bacteria

Zinc-Catalyzed Hydroboration of Carbon Dioxide Amplified by Borane-Tethered Heteroscorpionate Bis(Pyrazolyl)methane Ligands

The borane-functionalized (BR2) bis(3,5-dimethylpyrazolyl)methane (LH) ligands 1a (BR2: 9-borabicyclo[3.3.1]nonane or 9-BBN), 1b (BR2: BCy2), and 1c (BR2: B(C6F5)2) were synthesized by the allylation-hydroboration of LH. Metalation of 1a,b with ZnCl2 yielded the heteroscorpionate dichloride complexes [(1a,b)ZnCl2] 3a,b. The reaction of 1a with ZnEt2 led to the formation of the zwitterionic complex [Et(1a)ZnEt(THF)] 5. The reaction of complex 3a with two equivalents of KHBEt3 under a carbon dioxide (CO2) atmosphere gave rise to the formation of the dimeric bis(formate) complex [(1a)Zn(OCHO)2]2 8, in which its borane moieties intermolecularly stabilize the formate ligands of opposite metal centers. The allylated precursor Lallyl and its zinc dichloride, diethyl and bis(formate) complexes [(Lallyl)ZnCl2] 2, [(Lallyl)ZnEt2] 4, and [(Lallyl)Zn(OCHO)2] 7 were also isolated. The catalyst systems composed of 1 mol % of 3a or 3b and two equivalents of KHBEt3 hydroborated CO2 at 1 bar with pinacolborane (HBPin) to the methanol-level product H3COBPin (and PinBOBPin) in yields of 42 or 86%, respectively. The catalyst systems using the unfunctionalized complex [(LH)ZnCl2] 6 and KHBEt3 or KHBEt3/nOctBR2 (BR2: 9-BBN or BCy2) hydroborated CO2 to H3COBPin but in 2.5- to 6-fold lower activities than those exhibited by 3a,b/KHBEt3. The hydroboration of CO2 using 8 as a catalyst led to yields of 39-43%, comparable to those obtained with 3a/KHBEt3. The results confirmed that the catalytic intermediates benefit from the incorporated boranes' intra- or intermolecular stabilizations.

Synthesis, characterization, and antibacterial activities of a heteroscorpionate derivative platinum complex against methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is one of the species with the greatest clinical importance and greatest impact on public health. In fact, methicillin-resistant S. aureus (MRSA) is considered a pandemic pathogen, being essential to develop effective medicines and combat its rapid spread. This study aimed to foster the translation of clinical research outcomes based on metallodrugs into clinical practice for the treatment of MRSA. Bearing in mind the promising anti-Gram-positive effect of the heteroscorpionate ligand 1,1’-(2-(4-isopropylphenyl)ethane-1,1-diyl)bis(3,5-dimethyl-1H-pyrazole) (2P), we propose the coordination of this compound to platinum as a clinical strategy with the ultimate aim of overcoming resistance in the treatment of MRSA. Therefore, the novel metallodrug 2P-Pt were synthetized, fully characterized and its antibacterial effect against the planktonic and biofilm state of S. aureus evaluated. In this sense, three different strains of S. aureus were studied, one collection strain of S. aureus sensitive to methicillin and two clinical MRSA strains. To appraise the antibacterial activity, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) were determined. Moreover, successful outcomes on the development of biofilm in a wound-like medium were obtained. The mechanism of action for 2P-Pt was proposed by measuring the MIC and MBC with EDTA (cation mediated mechanism) and DMSO (exogenous oxidative stress mechanism). Moreover, to shed light on the plausible antistaphylococcal mechanism of this novel platinum agent, additional experiments using transmission electron microscopy were carried out. 2P-Pt inhibited the growth and eradicated the three strains evaluated in the planktonic state. Another point worth stressing is the inhibition in the growth of MRSA biofilm even in a wounded medium. The results of this work support this novel agent as a promising therapeutic alternative for preventing infections caused by MRSA.

Methacrylate Cationic Nanoparticles Activity against Different Gram-Positive Bacteria

Nanotechnology is a developing field that has boomed in recent years due to the multiple qualities of nanoparticles (NPs), one of which is their antimicrobial capacity. We propose that NPs anchored with 2-(dimethylamino)ethyl methacrylate (DMAEMA) have antibacterial properties and could constitute an alternative tool in this field. To this end, the antimicrobial effects of three quaternised NPs anchored with DMAEMA were studied. These NPs were later copolymerized using different methylmethacrylate (MMA) concentrations to evaluate their role in the antibacterial activity shown by NPs. Clinical strains of Staphylococcus aureus, S. epidermidis, S. lugdunensis and Enterococcus faecalis were used to assess antibacterial activity. The minimal inhibitory concentration (MIC) was determined at the different concentrations of NPs to appraise antibacterial activity. The cytotoxic effects of the NPs anchored with DMAEMA were determined in NIH3T3 mouse fibroblast cultures by MTT assays. All the employed NPs were effective against the studied bacterial strains, although increasing concentrations of the MMA added during the synthesis process diminished these effects without altering toxicity in cell cultures. To conclude, more studies with other copolymers are necessary to improve the antibacterial effects of NPs anchored with DMAEMA.

A bis(pyrazolyl)methane derivative against clinical Staphylococcus aureus strains isolated from otitis externa

OBJECTIVE

The purpose of this study was to evaluate the in vitro antibacterial effects of a p-Cymene-based bis(pyrazolyl)methane derivative (SC-19) to advance in developing alternative therapeutic compounds to fight against bacterial isolates from patients with otitis externa (OE).

METHODS

Eighteen swab specimens were collected from patients aged over 18 years diagnosed with OE within at least 7 days of symptom onset, contaminated by only one bacterium type: Pseudomonas aeruginosa (n = 5); Staphylococcus aureus (n = 8); Klebsiella aerogenes (n = 2); Serratia marcescens (n = 1); Morganella morganii (n = 2). To appraise antibacterial activity, minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) assays were run at different SC-19 concentrations.

RESULTS

When using SC-19, S. aureus strains showed less bacterial growth, but no bactericidal effect was observed. The MIC and MBC of SC-19 were 62.5 and 2000 μg/ml against S. aureus and were >2000 μg/ml against the other isolates obtained from OE, respectively. In addition, the MBICs and MBECs of SC-19 against S. aureus were 125 and >2000 μg/ml, respectively.

CONCLUSION

Nowadays the acquired antibiotic resistance phenomenon has stimulated research into novel and more efficient therapeutic agents. Hence, we report that, helped by the structural diversity fostered herein by a range of bis(pyrazolyl)methane derivatives, SC-19 can be a promising alternative therapeutic option for treating OE caused by S. aureus given the observed effects on both planktonic state and biofilm.

LEVEL OF EVIDENCE

IV.

Hercynite silica sulfuric acid: a novel inorganic sulfurous solid acid catalyst for one-pot cascade organic transformations

Herein, we delignated the synthesis of a novel inorganic sulfurous magnetic solid acid catalyst by the immobilization of an extremely high content of sulfuric acid functionalities on the amorphous silica-modified hercynite nanomagnetic core–shell via a simple method. Silica sulfuric acid (SSA) modified hercynite nanocomposite (hercynite@SSA) combines excellent recoverability and stability characteristics of hercynite (which can be regarded as a ferro spinel with Fd3m space group and cubic crystal structure) with the strong Brønsted acid properties of –SO₃H groups. This nanomagnetic solid acid was found to be an efficient and facile strong solid acid catalyst for the synthesis of bis(pyrazolyl)methanes via two different one-pot multicomponent methodologies under green conditions. The hercynite@SSA catalyst shows excellent catalytic activity and reusability in the ethanolic medium among different solid acid materials. A plausible reaction mechanism is proposed for this synthesis.

A novel inorganic sulfurous nanomagnetic solid acid composite was synthesized and its catalytic activity was evaluated in the synthesis of bis(pyrazolyl)methane derivatives. The catalyst displayed excellent activity and recoverability under green conditions.