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Advances in Phenolic Based Complexes

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A Special Issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (30 April 2026) | Viewed by 18866

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Dr. Kiril B. Gavazov

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Department of Chemical Sciences, Medical University of Plovdiv, 4004 Plovdiv, Bulgaria
Interests: spectrophotometry; coordination compounds; ion association; solvent extraction; cloud point extraction; azo dyes; tetrazolium salts; vanadium; transition metals
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Special Issue Information

Dear Colleagues,

The significance of phenolic compounds as ligands is derived from their capacity to donate electrons through the hydroxyl group, form chelate complexes, stabilize disparate metal oxidation states, and participate in biological and catalytic processes. Their adaptable binding modes and chemical reactivity render them highly valuable in inorganic, bioinorganic, and analytical chemistry. Phenolic-based complexes are of significance in a variety of fields, including medicine, the food industry, catalysis, green chemistry, water treatment, soil remediation, environmental analysis, material science, drug delivery, nanomaterials, energy storage, and more.

The objective of this Special Issue is to provide a forum for the dissemination of research findings pertaining to complexes based on phenolic compounds. We invite interested parties to submit manuscripts for consideration. Contributions may take the form of full papers, briefs, or reviews.

Dr. Kiril B. Gavazov
Guest Editor

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

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Keywords

phenolic compounds
complexes
structure
properties
applications
analysis

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Published Papers (9 papers)

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Editorial

Jump to: Research, Review

9 pages, 222 KB

Open AccessEditorial

Editorial for the Special Issue “Advances in Phenolic Based Complexes”

by Kiril Gavazov

Molecules 2026, 31(15), 2593; https://doi.org/10.3390/molecules31152593 - 24 Jul 2026

Viewed by 328

Abstract

Research on phenolic compounds and their complexes continues to advance rapidly, driven by interdisciplinary efforts that expand both their fundamental scientific significance and practical applications. This Special Issue of Molecules presents recent developments in the chemistry and applications of these complexes through contributions from researchers across three continents. The published papers can be organized into five thematic sections: (i) synthesis and structural characterization; (ii) biological activity and therapeutic potential; (iii) analytical applications and sensors; (iv) nanotechnology and advanced delivery systems; and (v) metabolism and environmental factors. Among the contributions is a review article on the application of phenolic azobenzene ligands for cation complexation. Collectively, the eight contributions provide an up-to-date overview of the field, highlighting recent advances, emerging trends, innovative approaches, and future research directions in the chemistry and applications of phenolic-based complexes. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

Research

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23 pages, 5967 KB

Open AccessArticle

The Role of Phenolic Profile of Salt-Stressed Duckweed (Lemna minor) in Synthesis and Biological Activity of Green ZnO Nanoparticles

by Nikola Stamenković, Filip Nikolić, Aleksandar Matić, Dragana Antonić Reljin, Marija Milovančević, Danijela Paunović and Olga Radulović

Molecules 2026, 31(13), 2326; https://doi.org/10.3390/molecules31132326 - 2 Jul 2026

Viewed by 568

Abstract

This study investigated whether salinity during cultivation of the aquatic plant Lemna minor (duckweed) influences the phytochemical composition of plant extracts and the properties of green-synthesized zinc oxide nanoparticles (ZnO NPs). Duckweed was cultivated under 0, 10, and 100 mM NaCl, followed by Orbitrap metabolomic profiling, nanoparticle synthesis, physicochemical characterization, and evaluation of antioxidant and antimicrobial activities. Orbitrap analysis revealed pronounced salinity-dependent changes in extract composition, including increased abundance of several flavonoids, glycosylated flavones, and hydroxycinnamic acid derivatives in the order 0 < 10 < 100 mM. ZnO nanoparticle formation was supported by UV–Vis spectroscopy, which showed characteristic absorption features around 360 nm, and by powder X-ray diffraction (PXRD), which indicated the predominance of the hexagonal wurtzite ZnO phase in all samples. SEM–EDS analysis revealed Zn- and O-rich materials consisting of micron-scale aggregates and finer submicron structures. Raman spectra were dominated by fluorescence, which increased with salinity treatment and may reflect differences in surface-associated phytochemicals rather than substantial changes in the ZnO crystal structure. Nanoparticles synthesized using extracts from salt-stressed duckweed exhibited higher total phenolic content (up to 66.79 ± 0.15 µM GAE g⁻¹), antioxidant activity (up to 55.01 ± 0.21%), and antimicrobial activity against Staphylococcus haemolyticus D4-2-100/1 (inhibition zone up to 1.55 ± 0.05 cm). Although the mechanisms underlying these differences remain to be fully elucidated, the results suggest that salinity-induced changes in duckweed metabolism may influence the biological properties of the resulting nanomaterials. Overall, this study highlights the potential of manipulating cultivation conditions to modulate plant extract composition and, consequently, influence the characteristics and functionality of green-synthesized ZnO nanoparticles. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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23 pages, 1543 KB

Open AccessArticle

Phenolic-Rich Wild Edible Macrofungi: Antimicrobial Activity and Antioxidant Potential

by Elif Ildız and Elif Yürümez Canpolat

Molecules 2026, 31(6), 978; https://doi.org/10.3390/molecules31060978 - 14 Mar 2026

Viewed by 803

Abstract

This study evaluated the antimicrobial and antioxidant activities and chemical properties of four wild edible macrofungi—Tuber aestivum (Wulfen) Spreng., Terfezia claveryi Chatin, Agaricus arvensis Schaeff. and Bovistella utriformis (Bull.) Demoulin & Rebriev—collected from different regions of Türkiye, with particular emphasis on the role of phenolic compounds. Methanol and hexane extracts were assessed for antimicrobial activity against Gram-positive, Gram-negative, multidrug-resistant (MDR) bacterial strains, and Candida albicans using minimum inhibitory concentration (MIC) assays. Total phenolic content (TPC) was determined, and antioxidant capacities were evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric reducing antioxidant power), and CUPRAC (cupric ion reducing antioxidant capacity) assays. The chemical profiles of hexane extracts were characterized by GC–MS analysis, whereas methanol extracts were analyzed by LC–MS/MS. Methanol extracts with high content of phenolic compounds exhibited markedly higher antimicrobial activity than hexane extracts, especially against Gram-positive bacteria. B. utriformis and A. arvensis displayed the highest phenolic contents (29.61 ± 0.6 and 27.14 ± 0.59 mg GAE/g DW, respectively) and antioxidant activities, revealing a strong positive correlation between TPC and antioxidant capacity. LC–MS/MS analysis revealed catechin, cinnamic acid, and caffeic acid as prominent phenolic constituents, highlighting the role of polyphenols in the observed bioactivity. GC–MS profiling predominantly identified fatty acid methyl esters, particularly linoleic and oleic acids, together with minor phenolic derivatives, suggesting a possible synergistic interaction contributing to the overall biological potential. The results highlight phenolic-rich macrofungi as valuable natural sources of antioxidant and antimicrobial agents with potential applications. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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23 pages, 4464 KB

Open AccessArticle

Synthesis of First Copper Metal Complex of C=C Extended Curcuminoid Analogue: Structure, β-Cyclodextrin Association, and Biological Properties

by Rosario Tavera-Hernández, Rubén Sánchez-Obregón, Marco A. Obregón-Mendoza, Antonio Nieto-Camacho, María Teresa Ramírez-Apan, Leidys L. Pérez-González and Raúl G. Enríquez

Molecules 2025, 30(19), 3943; https://doi.org/10.3390/molecules30193943 - 1 Oct 2025

Viewed by 1136

Abstract

The search for bioactive compounds against chronic diseases such as cancer and diabetes includes curcuminoids as promising scaffolds. Here, we report the synthesis of a family of curcuminoid analogue compounds with an extended unsaturated central chain, as follows: difluoroboron complex 1, the enolised curcuminoid 2, and its homoleptic copper complex 3, in moderate to good yields (68–90%). Additionally, their β-cyclodextrin (BCD) association complexes, 4 and 5, were prepared through a mechanochemical method and characterised by spectroscopic techniques. Complete ¹H and ¹³C NMR assignments and NOESY correlations revealed unique solvent effects on the conformational disposition of compound 2, while the copper complex 3 displayed the highest extinction coefficient (1.20 × 10⁵ M⁻¹·cm⁻¹). Furthermore, the authentication of the polymorph of 1 and the new crystal structures of 2 and 3, determined by single-crystal X-ray analysis, were highlighted. Although the copper complex 3 initially exhibited the lowest a-glucosidase inhibitory activity (IC₅₀ > 100 µM), it showed a significant increase (IC₅₀ = 36.27 µM) upon association with BCD, reaching values comparable to the free ligand (IC₅₀ = 45.63 µM). Compounds 1–5 were non-toxic to healthy cells (COS-7), but compound 5 stands out as a promising candidate against this metabolic condition. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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23 pages, 7866 KB

Open AccessArticle

Anti-Helicobacter pylori Activity and Gastroprotective Effects of Diacetylcurcumin and Four Metal Derivatives

by Almanelly Agabo-Martínez, Erika Gomez-Chang, Erick Hernández-Hipólito, Elizabet Estrada-Muñiz, Carolina Escobedo-Martínez, Marco A. Obregón-Mendoza, Raúl G. Enríquez, Libia Vega and Irma Romero

Molecules 2025, 30(19), 3849; https://doi.org/10.3390/molecules30193849 - 23 Sep 2025

Viewed by 2735

Abstract

Helicobacter pylori is the main etiological factor of gastritis, peptic ulcers, and gastric cancer. This bacterium’s antibiotic resistance has led to a lower eradication rate; therefore, new drugs with anti-H. pylori activity are needed. Curcumin exhibits multiple biological activities, but it has low stability and poor bioavailability. To overcome these disadvantages, different metal complexes have been synthesized. The objective of this study was to determine the in vitro anti-H. pylori activity of diacetylcurcumin (DAC), DAC₂-Cu, DAC₂-Zn, DAC₂-Mn, and DAC₂-Mg by obtaining the minimum inhibitory concentration of bacterial growth, and to investigate some mechanisms by which they could affect the bacteria (urease and DNA gyrase activities). Moreover, their gastroprotective potential was assayed in an ethanol-induced gastric ulcer model in mice. The results showed that DAC₂-Cu and DAC₂-Zn have good anti-H. pylori activity, exhibit specific activity against this bacterium, inhibit the urease activity, and provide 70% gastroprotection at a dose of 200 mg/kg of body weight. In a subacute toxicity study in mice, DAC₂-Cu and DAC₂-Zn did not cause death or any deleterious symptoms, nor did they have a significant effect on serum and urine biochemical parameters compared to control mice. These compounds are promising candidates for use in H. pylori eradication schemes. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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16 pages, 2833 KB

Open AccessArticle

Beer-Derived (Poly)phenol Metabolism in Individuals With and Without Metabolic Syndrome: A Comparative Dietary Intervention

by Daniel Hinojosa-Nogueira, Cristina María Díaz-Perdigones, María José García-López, Ascensión Marcos, María P. Portillo, Rosa María Lamuela-Raventós, Alba Subiri-Verdugo, Esther Nova, Iñaki Milton-Laskibar, Polina Galkina, Francisco J. Tinahones and Isabel Moreno-Indias

Molecules 2025, 30(14), 2932; https://doi.org/10.3390/molecules30142932 - 11 Jul 2025

Cited by 1 | Viewed by 1655

Abstract

The consumption of low-alcohol fermented beverages has been related to cardiovascular health improvements. Although the underlying mechanism is not completely understood, (poly)phenols have been proposed as one of the mediators. The objective of this study was to evaluate the impact of a controlled intervention with beer on (poly)phenols metabolism in individuals with and without metabolic syndrome (MetS). 20 participants (MetS and control) who consumed a standardized amount of beer during 6 weeks were recruited. Phenolic compounds were assessed in urine. Different changes in phenolic compounds associated with chronic beer consumption were found, particularly related to hesperetin conjugates and to the degradation of phenolic compounds derived from flavonoids and lignans. Noteworthily, MetS and control participants differed in baseline urine phenolic compound profiles and in their metabolization. Significant differences were found in the production and excretion of key (poly)phenols-derived metabolites, such as increased naringenin phase II conjugates in healthy subjects, or increased bacterial flavonoid catabolites. Certain relationships were observed between the phenolic compounds with metabolic and anthropometric variables. These findings suggest that beer-derived (poly)phenols are differentially metabolized according to metabolic-health status, and that they may contribute to certain metabolic health benefits through the modulation of specific metabolic pathways. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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16 pages, 3538 KB

Open AccessArticle

A Semi-Micro Extraction Spectrophotometric Determination of Iron Using 4-Nitrocatechol and Xylometazoline Hydrochloride

by Petya V. Racheva, Antoaneta D. Saravanska, Galya K. Toncheva, Denitsa D. Kiradzhiyska, Nikolina P. Milcheva, Vidka V. Divarova, Ina P. Pencheva, Kirila T. Stojnova, Vassil B. Delchev and Kiril B. Gavazov

Molecules 2025, 30(4), 899; https://doi.org/10.3390/molecules30040899 - 15 Feb 2025

Cited by 4 | Viewed by 2886

Abstract

A chromogenic solvent extraction system for Fe(III) based on 4-nitrocatechol (4NC) and xylometazoline hydrochloride (XMH) was investigated. The optimum conditions for extraction spectrophotometric determination of iron were found. Under these conditions, the formula of the extracted complex was (XMH⁺)₃[Fe(4NC)₃] and the apparent molar absorption coefficient at λ_max = 464 nm was 1.9 × 10⁵ dm³ mol⁻¹ cm⁻¹ (4-fold enrichment). To validate the aforementioned formula and gather information about the spin state of the central Fe(III) ion, a combined experimental-theoretical approach was employed. This approach entailed the experimental determination of the 4NC:Fe and XMH:Fe molar ratios and the optimization of potential color-bearing structures utilizing the B3LYP/6-311G computational chemistry method. The effect of foreign ions was thoroughly examined, and a sensitive, simple, and inexpensive analytical procedure was proposed, which was successfully applied for determining iron in pharmaceutical and industrial samples. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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19 pages, 4662 KB

Open AccessArticle

Preparation and Properties of Chitosan Complexes Consisting of Artemisia argyi Volatile Oil Nanoemulsion

by Shun Zhang, Kewei Zuo, Lijun Zhang, Chenlu Zhang and Juan Shi

Molecules 2025, 30(3), 585; https://doi.org/10.3390/molecules30030585 - 27 Jan 2025

Cited by 5 | Viewed by 3430

Abstract

Artemisia argyi volatile oil (AAVO) is a kind of natural oil with abundant active components and remarkable medicinal and healthcare value. However, AAVO has low solubility, stability, and bioavailability. Here, to address these issues, a nanoemulsion system of Artemisia argyi volatile oil (AAVO-Ne) is constructed using phase transition titration, and the conditions are continuously optimized to combine it with chitosan, forming a chitosan composite of the volatile oil nanoemulsion (AAVO-NeCs). The structure was analyzed using Fourier transform infrared (FT-IR) spectroscopy, and the performance was evaluated through in vitro antibacterial tests, in vitro release experiments, and antioxidant assays. The results indicated that the typical characteristic absorption peaks of AAVO shifted in the AAVO-Ne spectrum and new absorption peaks appeared in the AAVO-NeCs, which implied that the formation of AAVO-NeCs involved not only a physical encapsulation process but also certain chemical interactions, thus enhancing the stability and bioactivity of the composites. Compared to AAVO, AAVO-NeCs exhibited a 1.87-fold increase in antibacterial activity against antibiotic-resistant bacteria. Meanwhile, the in vitro release study demonstrated that AAVO-NeCs exhibited a biphasic release pattern. Compared to AAVO-Ne and AAVO, AAVO-NeCs also showed a significant enhancement in antioxidant activity. Overall, AAVO-NeCs demonstrate improved solubility and efficacy of AAVO, as well as high-efficiency delivery, antibacterial, sustained-release, and antioxidant properties. These attributes position AAVO-NeCs as a promising candidate for applications in drug delivery, food preservation, and other fields, offering innovative solutions and contributing to the sustainable development of related industries. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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Review

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35 pages, 6952 KB

Open AccessReview

Phenolic Azobenzene as Ligand for Cation Complexation—Syntheses and Applications

by Jan Hočevar, Jernej Iskra and Estelle Leonard

Molecules 2025, 30(12), 2499; https://doi.org/10.3390/molecules30122499 - 6 Jun 2025

Cited by 6 | Viewed by 3894

Abstract

Phenolic azobenzenes have garnered significant attention as functional materials due to their ability to undergo reversible photoisomerization and their potential for cation complexation. This review aims to provide a comprehensive overview of the recent developments in the synthesis, properties, and applications of phenolic azobenzene derivatives in cation binding and complexation. This article explores various synthetic strategies for the preparation of phenolic azobenzenes. Additionally, the mechanisms of cation complexation, including the role of the phenolic hydroxyl group and the azobenzene scaffold, are discussed, along with insights into the coordination chemistry involved. This review further examines the diverse applications of phenolic azobenzene complexes in fields such as ion sensing, catalysis, and biological and DSSC applications. Full article

(This article belongs to the Special Issue Advances in Phenolic Based Complexes)

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