Multiple dynamics of aroylhydrazone induced by mutual effect of solvent and light - spectroscopic and computational study

Cuminaldehyde-3-hydroxy-2-napthoichydrazone: Synthesis, effect of solvents, nonlinear optical activity, antioxidant activity, antimicrobial activity, and DFT analysis

Hydrazones derived from essential oil components have attracted considerable interest because of their antimicrobial, antioxidant, and nonlinear optical applications. In the present work, a new essential oil component derivative (EOCD), cuminaldehyde-3-hydroxy-2-napthoichydrazone (CHNH), was synthesized. EOCD was characterized by Fourier transform infrared spectroscopy, mass spectrometry, nuclear magnetic resonance (1H and 13C) spectroscopy, elemental analysis, ultraviolet-visible absorption spectroscopy, and field-emission scanning electron microscopy. Thermogravimetric analysis and X-ray diffraction showed a higher stability, phase-pure, and non-existent isomorphic phase transition in EOCD. Solvent studies indicated that the normal emission band was caused by the locally excited state and the large Stokes shifted emission originated because of the twisted intramolecular charge transfer. The EOCD possessed higher direct and indirect band gap energies of 3.05 eV and 2.90 eV respectively, as determined by the Kubelka-Munk algorithm. The outcomes of frontier molecular orbitals, global reactivity descriptors, Mulliken, and molecular electrostatic potential surface by density functional theory calculations revealed high intramolecular charge transfer, good realistic stability, and high reactiveness of EOCD. The hydrazone EOCD exhibited higher hyperpolarizability (18.248 × 10-30 esu) in comparison to urea. Antioxidant test results indicated that EOCD showed significant antioxidant activity (p < 0.05), as determined by the DPPH radical scavenging assay. The newly synthesized EOCD showed no antifungal activity against Aspergillus flavus. Additionally, the EOCD showed good antibacterial activity against Escherichia coli and Bacillus subtilis.

UV Laser-Induced Phototransformations of Matrix-Isolated 5-Chloro-3-nitro-2-hydroxyacetophenone

Conformational changes of 5-chloro-3-nitro-2-hydroxyacetophenone were studied by experimental and theoretical methods. Phototransformations of the compound were induced in low-temperature argon matrices by using UV radiation, which was followed by FT-IR measurements. Two types of changes within the molecule were detected: rotations of the hydroxyl and acetyl groups. A new conformer without an intramolecular hydrogen bond was generated upon irradiation with λ = 330 nm, whereas the reverse reaction was observed at 415 nm.

Antimicrobial assesment of aroylhydrazone derivatives in vitro

Aroylhydrazones 1-13 were screened for antimicrobial and antibiofilm activities in vitro. N'-(2-hydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (2), N'-(5-chloro-2-hydroxyphenyl-methylidene)-3-pyridinecarbohydrazide (10), N'-(3,5-chloro-2-hydroxyphenylmethylidene)-3-pyridinecarbohydrazide (11), and N'-(2-hydroxy-5-nitrophenylmethylidene)-3-pyridinecarbohydrazide (12) showed antibacterial activity against Escherichia coli, with MIC values (in µmol mL-1) of 0.18-0.23, 0.11-0.20, 0.16-0.17 and 0.35-0.37, resp. Compounds 11 and 12, as well as N'-(2-hydroxy-3-methoxyphenylmethylidene)-3-pyridinecarbohydrazide (6) and N'-(2-hydroxy-5- methoxyphenylmethylidene)-3-pyridinecarbohydrazide (8) showed antibacterial activity against Staphylococcus aureus, with the lowest MIC values of 0.005-0.2, 0.05-0.12, 0.06-0.48 and 0.17-0.99 µmol mL-1. N'-(2-hydroxy-5-methoxyphenylmethylidene)-3-pyridinecarbohydrazide (7) showed antifungal activity against both fluconazole resistant and susceptible C. albicans strains with IC90 range of 0.18-0.1 µmol mL-1. Only compound 11 showed activity against C. albicans ATCC 10231 comparable to the activity of nystatin (the lowest MIC 4.0 ×10-2 vs. 1.7 × 10-2 µmol mL-1). Good activity regarding multi-resistant clinical strains was observed for compound 12 against MRSA strain (MIC 0.02 µmol mL-1) and compounds 2, 6 and 12 against ESBL+ E. coli MFBF 12794, with the lowest MIC for compound 12 (IC50 0.16 µmol mL-1). Anti-biofilm activity was found for compounds 2 (MBFIC 0.015-0.02 µmol mL-1 against MRSA) and 12 (MBFIC 0.013 µmol mL-1 against EBSL+ E. coli). In the case of compound 2 against MRSA biofilm formation, MBFIC values were comparable to those of gentamicin sulphate, whereas in the case of compound 12 and EBSL+ E. coli even more favourable activity compared to gentamicin was observed.