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Molecules

Molecules is a leading international, peer-reviewed, open access journal of chemistry published semimonthly online by MDPI.
Indexed in PubMed | Quartile Ranking JCR - Q2 (Biochemistry and Molecular Biology | Chemistry, Multidisciplinary)

All Articles (62,509)

Gallic acid (GA) exhibits excellent antioxidant properties but suffers from chemical instability due to its carboxyl group, which limits practical application. To address this, we designed and investigated 14 distinct ester derivatives of GA, which were categorized into two major groups based on their substituents: chain alkyl and hydroxyl-substituted alkyl groups. Systematic evaluation revealed a striking decline in the DPPH radical scavenging activity of alkyl esters with increasing carbon chain length, from 91.9% for GA-C3 to 55.6% for GA-C30. The hydroxyl-functionalized GA esters GA-EG, GA-GL, and GA-PT maintain high antioxidant activity (>90%) while improving applicability through carboxyl substitution. In the oil system, all derivatives significantly prolong the oxidation induction time, with GA-C3 exhibiting the highest performance by extending the induction time by 2.15 h. Hydroxyl-functionalized esters such as GA-EG, GA-GL, and GA-PT also demonstrated significant efficacy, prolonging oxidation induction by 1.92 to 2.03 h. The results suggest how the structure of GA esters affects their antioxidant behavior, providing a direction for designing antioxidants suitable for specific systems.

7 January 2026

Chemical structure of GA-C10.

TS-1 zeolite and a series of Zr-modified samples (TS-1/xZr) were synthesized and systematically characterized to investigate the influence of zirconium incorporation on structural, textural, and photocatalytic properties. The structural and textural properties of the samples were examined by XRD and nitrogen adsorption isotherms. Elemental analysis (EDXRF, SEM/EDS) and FTIR confirmed successful incorporation of Zr into the TS-1 framework. Photocatalytic tests under white light irradiation using crystal violet (CV), methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes revealed enhanced degradation efficiency for the Zr-containing samples, particularly TS-1/10Zr. Kinetic modeling using pseudo-first-order (PFO) and pseudo-second-order (PSO) approaches indicated that dye degradation followed mainly PSO kinetics. Reusability studies demonstrated sustained stability and recyclability of the catalysts. The improved photocatalytic performance is attributed to synergistic electronic effects between Ti and Zr species, which enhance charge separation and light absorption.

7 January 2026

The current study aims to model the potential energy surface (PES) of three much less investigated hydroxyaryl(hetaryl)idene azomethine imine derivatives, possessing the same proton crane unit—namely the azomethine imine moiety—but slightly differing in the structure of the proton transfer platform (stator), by applying the tools of computational chemistry. The obtained calculational results are compared with already reported experimental structural, 1H NMR, and UV absorption spectra in an attempt to shed light on the observed data, mainly with regard to the efficiency of the excited state intramolecular proton transfer.

7 January 2026

The growing problem of antimicrobial resistance emphasizes the urgent need for new and effective natural antimicrobial agents. This study assessed the antibacterial activity of twenty essential oils and one absolute against Escherichia coli and examined the relationship between their chemical composition and biological activity. The chemical profiles of the samples were determined using gas chromatography–mass spectrometry (GC–MS), and the resulting data were analysed using principal component analysis (PCA), discriminant analysis (DA), and partial least squares (PLS) methods to explore associations between composition and antibacterial activity. The results showed substantial variability among the tested essential oils, with those from Thymus vulgaris, Aniba rosaeodora, Syzygium aromaticum, Pimenta dioica, and the absolute of Evernia prunastri exhibiting the strongest activity. GC–MS analysis identified thymol, eugenol, and methyl atrarate as key bioactive constituents associated with strong antibacterial effects, while linalool, limonene, and α-terpineol were linked to moderate activity. Multivariate analyses provided further insight but were limited by data variability, highlighting compositional diversity rather than clear group separation. Overall, the findings demonstrate that essential oils are a promising source of natural antimicrobial agents and emphasise the importance of linking chemical composition with biological function to understand their potential therapeutic applications.

7 January 2026

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Molecules - ISSN 1420-3049