Since the last few years, the growing interest in the use of natural and synthetic antioxidants as functional food ingredients and dietary supplements, is observed. The imbalance between the number of antioxidants and free radicals is the cause of oxidative damages of proteins, lipids, and DNA. The aim of the study was the review of recent developments in antioxidants. One of the crucial issues in food technology, medicine, and biotechnology is the excess free radicals reduction to obtain healthy food. The major problem is receiving more effective antioxidants. The study aimed to analyze the properties of efficient antioxidants and a better understanding of the molecular mechanism of antioxidant processes. Our researches and sparing literature data prove that the ligand antioxidant properties complexed by selected metals may significantly affect the free radical neutralization. According to our preliminary observation, this efficiency is improved mainly by the metals of high ion potential, e.g., Fe(III), Cr(III), Ln(III), Y(III). The complexes of delocalized electronic charge are better antioxidants. Experimental literature results of antioxidant assays, such as diphenylpicrylhydrazyl (DPPH) and ferric reducing activity power assay (FRAP), were compared to thermodynamic parameters obtained with computational methods. The mechanisms of free radicals creation were described based on the experimental literature data. Changes in HOMO energy distribution in phenolic acids with an increasing number of hydroxyl groups were observed. The antioxidant properties of flavonoids are strongly dependent on the hydroxyl group position and the catechol moiety. The number of methoxy groups in the phenolic acid molecules influences antioxidant activity. The use of synchrotron techniques in the antioxidants electronic structure analysis was proposed.

We discussed and summarized the latest data from the global literature on the action of polyphenolic antioxidants and their metal complexes. The review also includes a summary of the outcomes of theoretical computations and our many years of experimental experience. We employed various methods, including spectroscopy (FT-IR, FT-Raman, NMR, UV/Vis), X-ray diffraction, thermal analysis, quantum calculations, and biological assays (DPPH, ABTS, FRAP, cytotoxicity, and genotoxicity tests). According to our research, the number and position of hydroxyl groups in aromatic rings, as well as the delocalization of electron charge and conjugated double bonds, have a major impact on the antioxidant effectiveness of the studied compounds. Another important factor is metal complexation, whereby high ionic potential metals (e.g., Fe(III), Cr(III), Cu(II)) enhance antioxidant properties by stabilizing electron charge, while the low ionic potential metals (e.g., Ag(I), Hg(II), Pb(II)) reduce efficacy by disrupting electron distribution. However, we observed no simple correlation between ionic potential and antioxidant capacity. This paper gives insights that will aid in identifying new, effective antioxidants, which are vital for nutrition and the prevention of neurodegenerative illnesses. Our results outline the connections between biological activity and molecular structure, offering a foundation for the methodical design of antioxidants. Our review also shows in detail how we use various complementary methods to assess the impact of metals on the electronic systems of ligands. This approach moves beyond the traditional “trial and error” method, allowing for the more efficient and rational development of future antioxidants.

For many years, metal–flavonoid complexes have been widely studied as a part of drug discovery programs, but in the last decade their importance in materials science has increased significantly. A deeper understanding of the role of metal ions and flavonoids in constructing simple complexes and more advanced hybrid networks will facilitate the assembly of materials with tailored architecture and functionality. In this Review, we highlight the most essential data on metal–flavonoid systems, presenting a promising alternative in the design of hybrid inorganic–organic materials. We focus mainly on systems containing Cu^II/I and Fe^III/II ions, which are necessary in natural and industrial catalysis. We discuss two kinds of interactions that typically ensure the formation of metal–flavonoid systems, namely coordination and redox reactions. Our intention is to cover the fundamentals of metal–flavonoid systems to show how this knowledge has been already transferred from small molecules to complex materials.

The inhibiting activity of three yeast strains belonging to Pichia kudriavzevii, Pichia occidentalis, and Meyerozyma quilliermondii/Meyerozyma caribbica genera against common plant pathogens representing Mucor spp., Penicillium chrysogenum, Penicillium expansum, Aspergillus flavus, Fusarium cereals, Fusarium poae, as well as Botrytis cinerea genera was investigated. The yeast strains tested had a positive impact on growth inhibition of all target plant pathogens. The degree of inhibition was more than 50% and varied depending on both the yeast antagonist and the mold. Ethyl esters of medium-chain fatty acids, phenylethyl alcohol, and its acetate ester prevailed among the analyzed volatile organic compounds (VOCs) emitted by yeasts in the presence of the target plant pathogens. Due to the method used, assuming no contact between the antagonist and the pathogen, the antagonistic activity of the yeast strains studied resulted mainly from the production of biologically active VOCs. Moreover, the antagonistic activity was not only restricted to a single plant pathogen but effective towards molds of different genera, making the yeast strains studied very useful for potential application in biological control.

Purpose: Alpha-hydroxy acids (AHAs) are one of the classes of hydroxy acids being beneficial for human health. The manuscript summarizes the biological properties of two popular members of AHAs, i.e., Mandelic Acid (MA) and Gallic Acid (GA), with particular emphasis on antimicrobial properties. Moreover, attempts to design new derivatives improving the natural properties of AHAs by using the chemical and physical approach are discussed. Methods: Antimicrobial properties of MA, an arylalkyl AHA containing phenyl group attached to α-carbon, and GA, an aromatic trihydroxybenzoic acid containing the phenolic ring and carboxylic acid functional group, and their derivatives against common human and plant pathogenic fungi have been reviewed. Results: The antimicrobial activity of MA and GA is a complex phenomenon strictly correlated with other properties exhibited by these acids, e.g., pro-oxidative activity and hydrophobicity. In most cases, the acids derivatives exhibited higher antimicrobial activity than the acids themselves. This is probably because of the higher lipophilicity of moiety that allows better penetration through the cell membrane. Conclusion: MA and GA present an excellent health-promoting tool and are valuable starting materials for the design of new compounds such as metal complexes with alkali, or alkali earth metals. The lipophilic, antimicrobial, and pro-oxidative properties act synergistically supporting the pharmacological and therapeutic effect of acids and their derivatives.

Cinnamic acid (CA), p-coumaric acid (4-hydroxycinnamic acid, 4-HCA), caffeic acid (3,4-vdihydroxycinnamic acid, 3,4-dHCA), and 3,4,5-trihydroxycinnamic acid (3,4,5-tHCA) were studied for their structural, anti-/pro-oxidant properties and biodegradability. The FT-IR, FT-Raman, UV/Vis, ¹H and ¹³C NMR, and quantum chemical calculations in B3LYP/6-311++G** were performed to study the effect on number and position of hydroxyl group in the ring on the molecular structure of molecules. The antioxidant properties of the derivatives were examined using DPPH^● and HO^● radicals scavenging assays, ferric ion reducing antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC), inhibition of linoleic acid oxidation, as well as the biological antioxidant assay with Saccharomyces cerevisiae. Moreover, the pro-oxidant activity of compounds in Trolox oxidation assay was estimated. The effect of the derivatives on environment on the basis of increasing the carbon and nitrogen compounds transformation processes occurring in biological wastewater treatment was studied.