Enzymatic Synthesis of a Novel Coumarin Aminophosphonates: Antibacterial Effects and Oxidative Stress Modulation on Selected E. coli Strains

The objective of the present study was to evaluate the synergistic effect of two important pharmacophores, coumarin and α-amino dimethyl phosphonate moieties, on antimicrobial activity toward selected LPS-varied E. coli strains. Studied antimicrobial agents were prepared via a Kabachnik-Fields reaction promoted by lipases. The products were provided with an excellent yield (up to 92%) under mild, solvent- and metal-free conditions. A preliminary exploration of coumarin α-amino dimethyl phosphonate analogs as novel antimicrobial agents was carried out to determine the basic features of the structure responsible for the observed biological activity. The structure-activity relationship revealed that an inhibitory activity of the synthesized compounds is strongly related to the type of the substituents located in the phenyl ring. The collected data demonstrated that coumarin-based α-aminophosphonates can be potential antimicrobial drug candidates, which is particularly crucial due to the constantly increasing resistance of bacteria to commonly used antibiotics.

Synthesis and potential antimicrobial activity of novel α-aminophosphonates derivatives bearing substituted quinoline or quinolone and thiazole moieties

To develop novel antimicrobial agents, and based on the biologically active heterocyclic quinoline and thiazole substituted, a series of novel α-aminophosphonates (9a–h) and (10i–l) derivatives that incorporated quinoline or quinolone, and coumarylthiazole or 5-phenylthiazol-2-amine moieties were designed and synthesized via Kabachnik–Fields reaction in the presence of ionic liquid under ultrasound irradiation. All the new compounds were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. The in vitro antimicrobial activity of all synthesized compounds were screened in terms of MIC values against the selected strains of Gram-negative and Gram-positive bacteria and two fungal strains using the broth micro-dilution method. The results showed that most of the tested compounds showed moderate inhibitory activities against both Gram‐positive and ‐negative bacteria compared with reference drugs. The following compounds 9e, 9g, 9h, 9i and 9f, 9g, 9h, 10k, 10l are the most active against Gram-positive and Gram-negative bacteria strains, respectively, with MIC values ranging between 0.25 and 128 μg/mL. The synthesized compounds 9b, 9c, 9f, 9g, 9h, 10k, and 10l exhibited excellent antifungal inhibition with MIC values ranging between 0.25 and 32 μg/mL. Structure–activity relationship revealed that the presence of coumarylthiazole moiety and hydroxyl in the quinoline group increased the inhibitory activity against microbial strains pathogens. These results confirm that the synthesized compounds can be potential antimicrobial drugs candidate.

Greener organic synthetic methods: Sonochemistry and heterogeneous catalysis promoted multicomponent reactions

Ultrasound is an essential technique to improve organic synthesis from the point of view of green chemistry, as it can promote better yields and selectivities, in addition to shorter reaction times when compared to the conventional methods. Heterogeneous catalysis is another pillar of sustainable chemistry being the recycling and reuse of the catalysts one of its great advantage. In the other hand, multicomponent reactions provide the synthesis of structurally diverse compounds, in a one-pot fashion, without isolation and purification of intermediates. Thus, the combination of these protocols has proved to be a powerful tool to obtain biologically active organic compounds with lower costs, time and energy consumption. Herein, we provide a comprehensive overview of advances on methods of organic synthesis that have been reported over the past ten years with focus on ultrasound-assisted multicomponent reactions under heterogeneous catalysis. In particular, we present pharmacologically important N- and O-heterocyclic compounds, considering their synthetic methods using green solvents, and catalyst recycling.

Synthesis and potent antimicrobial activity of novel coumarylthiazole α-aminophosphonates derivatives

Herein, we reported a novel series of α-aminophosphonates derivatives (IV)a-m bearing an important pharmacophore coumarylthiazole moiety. All the new compounds have been synthesized via Kabachnik-Fields reaction under ultrasonic irradiation. The products were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. All these compounds (IV)a-m were screened for their in vitro for antimicrobial activity against thirteen Gram-negative bacteria and five Gram-positive bacteria and Candida albicans strains. The results showed that all the synthesized compounds exhibited moderate antibacterial activities against both references and multidrug-resistant and antifungal strains. The compound (IV)e showed the highest activities against all pathogens of the tested microbial strains with MIC of 0.125 μg/mL. The compounds (IV)h, (IV)f, (IV)b, and (IV)d exhibited moderate and promising activities with MIC of 0.125 μg/mL. Structure-activity relationship revealed that inhibitory activity of the synthesized compounds is related to the type of the substituted group on phenyl rings, and these results showed that the electron-donating groups at ortho and para positions have a high relationship increasing antimicrobial activities than the electron-withdrawing groups. These results confirm that coumarylthiazole α-aminophosphonates compounds can be potential antimicrobial drugs candidate.

Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications

With the promising potential application of Ag/graphene-based nanomaterials in medicine and engineering materials, the large-scale production has attracted great interest of researchers on the basis of green synthesis. In this study, water-soluble silver/graphene oxide (Ag/GO) nanomaterials were synthesized under ultrasound-assisted conditions. The structural characteristics of Ag/GO were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersion spectroscopy, respectively. The results showed the silver particles (AgNPs) obtained by reduction were attached to the surface of GO, and there was a strong interaction between AgNPs and GO. The antibacterial activity was primarily evaluated by the plate method and hole punching method. Antibacterial tests indicated that Ag/GO could inhibit the growth of Gram-negative and Gram-positive bacteria, special for the Staphylococcus aureus.