Butylated hydroxy benzylidene ring: an important moiety for antioxidant synergism of semicarbazones
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Butylated hydroxy benzylidene ring: an important moiety for antioxidant synergism of semicarbazones Amit R. Nath1 · Wageeh A. Yehye1 · Mohd Rafie Bin Johan1 Received: 1 September 2019 / Accepted: 19 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The compounds having two or more antioxidant functions in their structure exhibit antioxidant synergism that generally increase the antioxidant activity of these compounds. In this study, two series of semicarbazone (7a–j and 7a′–j′) bearing butylated ortho and para hydroxy benzylidene ring were prepared for the investigation of antioxidant synergism. This study found that intramolecular hydrogen bond can form in semicarbazones due to the inappropriate position of hydroxyl group on benzylidene ring, which adversely affects the antioxidant synergism. As consequence, butylated para hydroxyl benzylidene phenyl semicarbazone (7a) (IC50 12.27 µM) showed ~ 4.3 times and ~ 2.7 times better antioxidant activity than compounds 7a′ (IC50 53.30 µM) and BHT (IC50 32.63 µM), respectively, in DPPH assay. In addition, based on the solubility in trimethylolpropane trioleate (TMPTO) as synthetic base oil and obtained I C50 results, oxidation stability of synthesized compounds was also evaluated by two kinds of differential scanning calorimeter (DSC) test, namely temperature ramping DSC and programmed temperature DSC. Thermogravimetric analysis is also performed for the thermal stability assessment. TMPTO incorporated with 0.25 mass% of 7c and 7e were found better oxidative (around 2 times) and thermal resistance than BHT. This DSC results showed another important aspect of semicarbazones that proper modification of semicarbazones can be used in the synthetic lubricant oil as a potential antioxidant. Thus, the results of this study are promising which can be taken under consideration to design and prepare more efficient multipotent semicarbazones. Graphic abstract Para
Oxidative problems
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Keywords Antioxidant synergism · DSC · Lubricant oil · Oxidative stability · TGA · Semicarbazones Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10973-020-10199-8) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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Introduction Oxidative stress is one of the main causes of etiology and expansion of major human deteriorating disease. The imbalance of production of free radical (reactive oxygen species) and the ability of the body to counteract the free radical cause oxidative stress [1, 2]. So excessive free radicals exert toxic effects throughout the body especially responsible for cancer and other chronic diseases [3, 4]. Apart from the oxidative stress in the human body, free radicals cause auto-oxidation and premature oxidation in industrial products such as oils, rubbers, food and foodstuffs [5–7]. Premature oxidatio
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