Physical and Theoretical Chemistry, Electrochemistry
13
Scopus Publications
Scopus Publications
Development of Biscoumarin Compounds With Quorum-Quenching Potential: Synthetic, Biological, and In Silico Studies Kathleen C. Pinto, Linus Coelho, Vinod K. Mandrekar, Hari K. Kadam, Milind Naik, Vishnu R. Chari Journal of Heterocyclic Chemistry, 2026 Coumarins are well known for their biological properties. A mild, efficient synthetic route is developed for biscoumarin compounds using ceric ammonium nitrate at room temperature. This method has broad substrate tolerance with 70%–97% isolated yield. The method also exemplified industrial utility as tested on a multigram scale, and particularly avoided column chromatography. Biscoumarin compounds prepared with diverse substitutions were screened for their quorum‐quenching (QQ) potential to serve as potential alternatives to antibiotics against pathogenic bacteria. QQ activity of the prepared compounds was determined by their ability to inhibit violacein pigment production of bioreporter Chromobacterium violaceum in a concentration‐dependent manner. Biscoumarins ( 1g , 1n , and 1d ) showed impressive QQ activity on C. violaceum and also revealed very good antibiofilm activity against gram‐negative ( Pseudomonas aeruginosa ATCC 27853 and Salmonella typhimurium ATCC 14028) and gram‐positive ( Staphylococcus aureus ATCC 6538) human pathogens via the QQ mechanism, indicating their versatile nature against diverse QS signaling systems (AHL, HAQs, and agr). Moreover, molecular docking studies further confirmed our results with impressive binding affinity −8.7, −8.5, and −8.4 kcal/mol ( 1n , 1g , and 1d ) to protein MvfR (PqsR) and binding affinity −9 kcal/mol to protein AgrA (transcription factor), both controlling the expression of virulence factors in P. aeruginosa and S. aureus , respectively. The present investigation highlights the potential of biscoumarin compounds in the medical field to treat life‐threatening infections as an alternative to antibiotics.
Synthesis, antibacterial activity, and cytotoxicity of newly synthesized carbon dots derived from dibasic carboxylic acids via conventional microwave-assisted method Pritesh Khobrekar, Fiona Fernandes, Aishwarya Angadi, Dviti Volvoikar, Vishnu Chari, Vishnu Nadkarni, Meenal Kowshik, Sandesh Bugde Journal of Dispersion Science and Technology, 2026 A simple, rapid, single-step microwave-assisted method was developed to prepare CQDs with narrow size distribution using dibasic carboxylic acids as a carbon source. The synthesized CQDs were well characterized using spectroscopic techniques such as P-XRD, FT-IR, high-resolution transmission electron microscopy (HR-TEM), UV-Vis absorption, and photoluminescence spectroscopy. The synthesized CQDs demonstrated excellent photostability, with particle size in the 1.5–6 nm range. The fluorescence quantum yield was found to be 28%, 7%, 13%, 38%, and 31% for CQD-AO, CQD-AT, CQD-AA, CQD-AS, and CQD-AM, respectively. Cytotoxicity tests and cellular uptake experiments of the CQDs further showed their viability in biomedical applications. All five synthesized CQDs showed effective antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This work is pivotal in advancing antibacterial nanomaterials, offering a promising alternative to conventional antibacterial agents.
Quorum quenching of virulence traits expression in human and plant pathogens by Isoxazolone and its molecular docking studies Komal S. Salkar, Lakshangy S. Charya, Milind M. Naik, Hari K. Kadam, Vishnu Chari Journal of Applied Biology and Biotechnology, 2025 Inhibiting quorum sensing (QS) to hinder extracellular polymeric substances (EPS) production and biofilm formation in pathogenic bacteria was studied as an efficient alternative for controlling the infections caused by multiple drug resistant (MDR) bacteria. In the present study, the isoxazolone derivative (4-(2-hydroxy-5-methoxybenzylidene)- 3-methylisoxazol-5(4H)-one) was tested for its ability to inhibit EPS production and biofilm formation in human as well as plant pathogenic bacteria. The binding affinity of the derivative to the quorum sensing regulatory proteins (AgrA and LasR) was investigated by carrying out molecular docking studies. The derivative was capable of substantially inhibiting EPS production and biofilm formation in Pseudomonas aeruginosa, Staphylococcus aureus, Erwinia carotovora, and Ralstonia solanacearum at subinhibitory concentrations. Furthermore, molecular docking studies confirmed our results with notable binding affinity −7.5 kcal/mol to transcriptional activator protein LasR and binding affinity −6.8 kcal/mol to AgrA (transcription factor), both controlling expression of virulence factors in P. aeruginosa and S. aureus, respectively. This is a first report that proves that isoxazolone derivatives have quorum quenching potential (QQ) against both human and plant pathogens, which can be applied in medical and agricultural fields.
Visible-light-induced aerobic C-3 thiocyanation of indoles using porphyrin as photoredox catalyst Pritesh P. Khobrekar, Pooja V. Shreechippa, Rutika R. Gawas, Ratan W. Jadhav, Vishnu R. Chari, Sheshanath V. Bhosale, Sandesh T. Bugde Synthetic Communications, 2025 In this work, we report a metal-free and environmentally friendly approach for the electrophilic C–H thiocyanation of indoles under visible light irradiation. Using porphyrin as a photocatalyst and atmospheric air as an oxidant, we developed a mild and efficient route to synthesize a series of thiocyanate products with both electron-rich and electron-deficient systems in moderate to good yields. The use of a radical scavenger like TEMPO helped to establish a photoredox mechanism. This method offers a sustainable and promising approach for synthesizing heterocyclic substrates, thiocyanate aromatics, and bioactive molecules through photoredox catalysis.
Ligand Backbone Influenced Luminescent Properties of Mononuclear Zn(II)-N3Py2 Compounds: Synthesis, Structures and Nitroaromatics Detection Jeffrey L. Viegas, Vishnu R. Chari, Sunder N. Dhuri Chemistryselect, 2024 Mononuclear Zn(II) compounds, [Zn(L1)](ClO4)2 (1) and [Zn(L2)](ClO4)2 (2), embedded with ligands, L1=N1‐(pyridin‐2‐ylmethyl)‐N2‐(2‐((pyridin‐2‐ylmethyl)amino)ethyl)ethane‐1,2‐diamine and L2=N1‐(pyridin‐2‐ylmethyl)‐N3‐(3‐((pyridin‐2‐ylmethyl)amino)propyl)propane‐1,3‐diamine are synthesized. Compound 1 is revisited, and structure‐function relation is compared with new compound 2. Single crystal X‐ray analysis revealed that compound 1 crystallizes in the tetragonal non‐centrosymmetric P41 space group while 2 crystallizes in a centrosymmetric monoclinic space group P21/c. The asymmetric unit consists of a crystallographically independent [Zn(L1)]2+cation in 1 while [Zn(L2)]2+cation in 2 and two unique perchlorate anions in both. IR spectra of 1 and 2 confirmed the vibrations due to organic ligands and tetrahedral perchlorates. PXRD confirmed the phase purity of powdered samples compared with theoretical PXRD patterns obtained from single‐crystal X‐ray diffraction data. NMR and ESI‐MS data suggested the phase purity and stability of compounds 1 and 2 in solution. Photoluminescence properties of compounds 1 and 2 have been investigated, considering their application in sensing explosive nitroaromatic compounds. Our results suggest that compound 1 is very selective in the chemical sensing of trinitrophenol (TNP) and dinitrophenol (DNP) in an aqueous medium compared to the reactivity of compound 2. The existence of spectral overlap in the absorption spectra of 2,4‐dinitrophenol (DNP) and 2,4,6‐trinitrophenol (TNP) with the emission spectrum of 1 or 2 indicates the operation of the resonance electron transfer (RET) mechanism.
9-Fluorenone Catalyzed Visible Light Oxidation of Hydrazides: An Efficient Route for the Synthesis of N,N′-Diacylhydrazines Derivatives Pritesh P. Khobrekar, Vishnu R. Chari, Sandesh T. Bugde Chemistryselect, 2024 A visible light‐mediated oxidative coupling of hydrazides into corresponding N,N’‐ diacylhydrazines using a commercially available and low‐cost metal‐free photocatalyst was reported. The versatility of the reaction has been demonstrated across a broad spectrum of functional groups present in hydrazides. Interestingly, the developed methodology was utilized to synthesize symmetrical and unsymmetrical N,N’‐diacylhydrazines in moderate yields. Density Functional Theory (DFT) calculations, along with control reactions and quenching studies, provide evidence supporting the proposed mechanism, favoring the photoredox pathway. Additionally, NMR and UV‐Vis studies confirmed the generation of H2O2 in the reaction mixture, which strengthens the proposed mechanism. To our knowledge, this is the first report for the conversion of hydrazides to N,N’‐diacylhydrazines using 9‐fluorenone as an organic photoredox catalyst.
