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.
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 of 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, hydrophobicity. In most cases, the acids derivatives exhibited higher antimicrobial activity than acids itself. 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.
Thin nanostructured block copolymer films were prepared using dilute solutions of partly tert-butoxycarbonyl (BOC)- and tert-butyl (TBU)-protected block copolymers based on 4-hydroxystyrene with varying block ratios. AFM measurements showed different nanostructures and morphologies of the films dependent on the block composition of the employed block copolymers. The nanostructure observed in thin films was compared to that of the bulk samples which was analyzed in detail by temperature-dependent SAXS measurements. In order to improve the regularity of the nanostructures of the as-prepared films, different film preparation techniques, film preparation parameters, and solvents were applied, and their impact on the film morphology was investigated. A complete removal of the BOC protecting groups in a block copolymer film was achieved by heating of a film at 190 °C. This process gave rise to the transformation of a partly BOC-protected block copolymer into the homopolymer poly(4-hydroxystyrene), and thus a switching of the thin film morphology occurred which was investigated by AFM, FI-IR, ellipsometry, and contact angle measurements.
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