Novel type of carbon‐centered antioxidants arylmethyl Meldrum's acids − inhibit free radicals

Abstract

Monosubstituted Meldrum's acids are found out as a new class of powerful antioxidants. These compounds act as carbon radical scavengers due to the presence of acidic hydrogen in the moiety of cyclic 1,3‐dicarbonyl compound. The presence of phenol and benzylic moiety is favored, but these structural elements are not crucial for the antiradical activity in polar media. The antiradical and antioxidant activity of the substituted Meldrum's acids is not significantly affected by the substituents in the aromatic ring. The 5‐substituted 1,3‐dioxan‐4,6‐diones demonstrate high scavenging capacity of free radicals. The inhibition of DPPH and GO achieved even ∼100 and 80%, respectively. All substituted Meldrum's acids are better antioxidants than BHT, and activity of some of them even exceed vitamin C. It is found out that in polar media the compounds act via SPLET mechanism. Substituted Meldrum's acids turned out as powerful antioxidants for inhibition of oxidation processes of fatty acid alkyl esters, too. The oxidative stability of the last with the title compound additive was significantly higher than with BHT additive. It seems, that the antioxidant activity of the substituted Meldrum's acids in fatty acid esters is both due to benzylic position and 1,3‐dicarbonyl moiety. Practical applications: Arylmethyl Meldrum's acids should be highlighted as potential antioxidants for increasing oxidative stability of various products containing, for example, esters of poly‐unsaturated fatty acids. It should be admitted that the structure of the title compounds can be widely modified by substituents in the aromatic ring without remarkable loss of antioxidant and antiradical activity, but other properties (like solubility) may be improved. In order to apply the title antioxidants into products like cosmetics additional tests regarding toxicity are required. However, these antioxidants can be recommended for increasing oxidative stability for products used in technique. Monosubstituted Meldrum's acids act as carbon radical scavengers due to the presence of acidic hydrogen in the moiety of cyclic 1,3‐dicarbonyl compound. The substituted Meldrum's acids demonstrate high scavenging capacity of free radicals DPPH and GO. These compounds turned out as powerful antioxidants for inhibition of oxidation processes of fatty acid alkyl esters. The antioxidant activity of the substituted Meldrum's acids in fatty acid esters is both due to benzylic position and 1,3‐dicarbonyl moiety. Few of the monosubstituted Meldrum's acids were better antioxidants than BHT, TBHQ, α‐tocopherol, or vitamin C.

Innovative Bio-Based Organic UV-A and Blue Light Filters from Meldrum’s Acid

“…Tests were performed by using DPPH (2,2-diphenyl-1-picrylhydrazyl) as a free radical and monitoring its disappearance, results are shown in Table 1. Antiradical properties for the phenolic series have already been described and are in accordance with those measured [33]. Within the furanic and pyrrolic series, only three derivatives demonstrate antiradical activity (5, 8, and 11) but with poor EC 50 values (>80 nmol).…”

“…All of the chemical structures were confirmed by 1 H-& 13 aldehydes for a more fundamental purpose (i.e., pyrroles). Through this straightforward and sustainable synthetic procedure, compounds are obtained in high purity and yield, similar to those described in the literature (49%-90%) [33]. Thanks to this simple and sustainable methodology, we populated a library of 14 molecules presenting different conjugation systems (Scheme 3).…”

“…Different reaction conditions have been investigated in the presence of ionic liquids [31] or in PEG-400 [32]. Nevertheless, the simplest and the greenest synthetic procedure remains the reaction in water as the compounds precipitate in water and can be isolated by a simple filtration, or otherwise they are simply obtained by liquid/liquid extraction, thus avoiding the use of expensive and waste-generating chromatography (Scheme 2) [33]. In order to offer renewable and bio-based products, we oriented our choice for aldehydes towards widely used p-hydroxybenzaldehyde (i.e., vanillin) and furanic compounds (i.e., furfural, obtained by dehydration of Thanks to this simple and sustainable methodology, we populated a library of 14 molecules presenting different conjugation systems (Scheme 3).…”

Review on the Regulation of Plant Polyphenols on the Stability of Polyunsaturated-Fatty-Acid-Enriched Emulsions: Partitioning Kinetic and Interfacial Engineering

“…It is because of the vastly different detection results caused by the various solvents to dissolve polyphenols. According to the studies, the density functional theory (DFT) has developed as the most suitable computational method to explore the relationship between the structure and antioxidant activity of polyphenols with medium and large molecular weights. − However, for polyphenols with lower molecular weight, it was more reliable to predict their antioxidative activity using various methods with different antioxidative mechanisms, such as FRAP for reducing capacity, DPPH • for free radical scavenging activity, ORAC for oxygen radical absorbance capacity, etc. More importantly, to avoid the influence caused by solvents on the antioxidative activity determination for small-molecule polyphenols, the solvent used to dissolve polyphenols should be the same as in the application system.…”

Crystal structure of 3-hydroxy-2-(4-hydroxy-3-methoxyphenylmethyl)-5,5-dimethylcyclohex-2-enone

“…Compound 1 demonstrates notable antiradical activity against free radicals. Free radical tests were realized according to the procedures described previously (Mierina et al, 2017). 1,1-Diphenyl-2-picrylhydrazyl test: inhibition, when molar ratio of the compound and free radical is 1:1, was 93.3AE2.5%; IC 50 was 23.0AE0.6 mM (starting concentration of free radical was 100 mM).…”