An efficient one pot syntheses of aryl-3,3'-bis(indolyl)methanes and studies on their spectral characteristics, DPPH radical scavenging-, antimicrobial-, cytotoxicity-, and antituberculosis activity

Chickpea leaf exudates: a green Brønsted acid type biosurfactant for bis(indole)methane and bis(pyrazolyl)methane synthesis

A clean and highly efficient protocol for green synthesis of bis(indole)methanes and bis(pyrazolyl)methanes has been successfully achieved by using a naturally sourced bio-surfactant, chickpea leaf exudates (CLE), as a Brønsted acid-type catalyst.

Novel synthetic bis-indolic derivatives with antistaphylococcal activity, including against MRSA and VISA strains

OBJECTIVES

We report the synthesis, antibacterial activity and toxicity of 24 bis-indolic derivatives obtained during the development of new ways of synthesis of marine bis-indole alkaloids from the spongotine, topsentin and hamacanthin classes.

METHODS

Innovative ways of synthesis and further structural optimizations led to bis-indoles presenting either the 1-(1H-indol-3'-yl)-1,2-diaminoethane unit or the 1-(1H-indol-3-yl)ethanamine unit. MIC determination was performed for reference and clinical strains of Staphylococcus aureus and CoNS species. MBC, time-kill kinetics, solubility, hydrophobicity index, plasma protein-binding and cytotoxicity assays were performed for lead compounds. Inhibition of the S. aureus NorA efflux pump was also tested for bis-indoles with no antistaphylococcal activity.

RESULTS

Lead compounds were active against both S. aureus and CoNS species, with MICs between 1 and 4 mg/L. Importantly, the same MICs were found for MRSA and vancomycin-intermediate S. aureus strains. Early concentration-dependent bactericidal activity was observed for lead derivatives. Compounds with no intrinsic antibacterial activity could inhibit the S. aureus NorA efflux pump, which is involved in resistance to fluoroquinolones. At 0.5 mg/L, the most effective compound led to an 8-fold reduction of the ciprofloxacin MIC for the SA-1199B S. aureus strain, which overexpresses NorA. However, the bis-indole compounds displayed a high hydrophobicity index and high plasma protein binding, which significantly reduced antibacterial activity.

CONCLUSIONS

We have synthesized and characterized novel bis-indole derivatives as promising candidates for the development of new antistaphylococcal treatments, with preserved activity against MDR S. aureus strains.

Molecular structure investigation of organic cocrystals of 1,10-phenanthroline-5,6-dione with aryloxyacetic acid: a combined experimental and theoretical study

Two organic cocrystals namely, 1,10-phenanthroline-5,6-dione:2-naphthoxyacetic acid [(phendione)(2-naa)] (1) and 1,10-phenanthroline-5,6-dione:2-formylphenoxyacetic acid [(phendione)(2-fpaa)] (2) were synthesized and studied by single crystal XRD, FT-IR, NMR, thermogravimetric, and powder X-ray diffraction analysis. The molecular properties of cocrystals were studied using density functional theory (DFT), basis set B3LYP/6-31G(d,p). Both cocrystals are stabilized through intermolecular hydrogen bonding (OH⋯N). The total electron density and molecular electrostatic potential surfaces of the cocrystals were constructed by NBO analysis using B3LYP/6-31G(d,p) method to display the electrostatic potential (electron+nuclei) distribution. The energy gap between HOMO and LUMO was measured for both cocrystals.

Inclusion complexation of phenoxyaliphatic acid derivatives of 3,3'-bis(indolyl)methanes with β-cyclodextrin

The inclusion complexation behavior of phenoxyaliphatic acid derivatives of 3,3'-bis(indolyl)methane (BIMs 1-5) with β-cyclodextrin (β-CD) were investigated in both solution and solid state by means of UV-Visible, fluorescence spectroscopy, FT-IR and (1)H NMR techniques. The nature of the host-guest inclusion complex between BIMs and β-CD has been elucidated. The experimental results confirmed the existence of 1:1 inclusion complex of BIMs with β-CD. The binding constants describing the extent of formation of the complexes have been determined using Benesi-Hildebrand plots using UV-Vis and fluorescence spectroscopy. BIMs exhibited an affinity for β-CD. The spectral studies suggested the phenyl ring along with alkyl substitutions of BIMs is present inside of β-CD cavity.

In situ Bronsted-Lowry acid catalyzed syntheses, characterization, single crystal XRD, electronic spectral-, DPPH radical scavenging-, and DNA protection studies of aryl-3,3'-bis(indolyl)methanes

A series of novel aryl-3,3'-bis(indolyl)methanes (BIMs) were synthesized using indole and formylphenoxyaliphatic acid(s) in water in the absence of any catalyst. The formylphenoxyaliphatic acid behaves as an in situ Bronsted-Lowry acid catalyst in water. UV-Visible and fluorescence spectra of the compounds were recorded in selected solvents. The gas phase geometry optimization of the compounds were achieved using DFT calculations at B3LYP/3-21G((*)) level of theory. The electronic properties, such as HOMO-LUMO energies were calculated using the above method based on the optimized structure. Compounds have better DPPH radical scavenging activity and reduction of oxidative damage of DNA.