Vishnu Rama Chari

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.

Glutathione reductase (GR) catalyzes the reduction of selenenyl sulfide (RSeSG) to glutathione (GSH) and selenol (RSeH).

Mononuclear Zn(II) compounds, [Zn(L ¹ )](ClO ₄ ) ₂ ( 1 ) and [Zn(L ² )](ClO ₄ ) ₂ ( 2 ), embedded with ligands, L ¹ = N ¹ ‐(pyridin‐2‐ylmethyl)‐ N ² ‐(2‐((pyridin‐2‐ylmethyl)amino)ethyl)ethane‐1,2‐diamine and L ² = N ¹ ‐(pyridin‐2‐ylmethyl)‐ N ³ ‐(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 P 4 ₁ space group while 2 crystallizes in a centrosymmetric monoclinic space group P 2 ₁ / c . The asymmetric unit consists of a crystallographically independent [Zn(L ¹ )] ²⁺ cation in 1 while [Zn(L ² )] 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.

Mononuclear nonheme copper(II) compounds [Cu(BQEN)(CH₃CN)]²⁺1 and [Cu(BQPN)(CH₃CN)]²⁺2 (BQEN = N,N′-dimethyl-N,N′-di(quinolin-8-yl)ethaneane-1,2-diamine; BQPN = N,N′-dimethyl-N,N′-di(quinolin-8-yl)propane-1,2-diamine) were synthesized and characterized by elemental analysis, ESI-MS, EPR, and single-crystal X-ray diffratrometry. Compound 1 crystalized in the P space group, while 2 crystallized in the P2₁/n group. Compounds 1 and 2 exhibited distorted square pyramidal geometry, which deviated interestingly by 4.8% and 46.0% from a regular square pyramidal structure in 1 and 2, respectively. This was attributed to the marginal increase in the carbon chain backbone of the ligand in 2. Compounds 1 and 2 were used in the aerial oxidation of 2-aminophenol (H₂AP) to 2-amino-phenoxazine-3-one (APX), which revealed phenoxazinone synthase activity. DFT steric maps were utilized to understand the catalytic activity of 1 (% Vbur, 71.3%) and 2 (% Vbur, 75.6%). The current results clearly demonstrate an interesting structure–function relationship based on the effect of the ligand backbone on the geometry.