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This work shows the synthesis, characterization, and thermo-oxidative study of 5-n-pentadecyl-2-tertbutylphenol [alkylphenol (AP)] before and after its incorporation into mineral lubricant oil. AP was synthesized by alkylation of hydrogenated cardanol. For this study, we employed thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and differential thermal analysis (DTA) techniques. Mineral lubricant oil was submitted to an accelerated oxidation test in the presence and absence of AP according to the modified ASTM D-2440 method. The addition of 1% AP to the oil has reduced the carbonyl and peroxide band areas: 1.00-1.00 (without AP) and 0.35-0.32, ROOH; 0.53-0.59, CdO (with AP), respectively. The results showed that AP significantly reduced the formation of oxidation products in the lubricant oil analyzed. TG-DTG curves showed that 5-n-pentadecyl-2-tertbutylphenol is more stable than 2,6-di-t-butyl-4-methylphenol (BHT), 158 against 87 °C for BHT. According to the integral procedural decomposition temperature (IPDT) values calculated on the basis of the TG thermograms, AP (IPDT of 268 °C) was recognized to be more thermally stable than BHT (IPDT of 162 °C). The techniques used for thermo-oxidative studies (TG-DTG, DSC, and DTA) showed a good correlation.

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This work presents the synthesis, characterization and the thermal study of 5-n-pentadecyl-2-tert-amylphenol (alkylphenol), which was synthesized by alkylation of 3-n-pentadecylphenol. For this study were employed termogravimetry (TG), derivative termogravimetry (DTG), differential scanning calorimetry (DSC), and differential thermal analysis (DTA) techniques. Hydrogenated naphthenic oil was submitted to accelerated oxidation tests in the presence and absence of alkylphenol according to modified ASTM D-2440 method. The addition of 1% of alkylphenol to the oil has reduced the carbonyl and peroxides bands areas: 1.00-1.00 (without alkylphenol) and 0.59-0.51 (with alkylphenol) respectively. The results showed that alkylphenol reduced significantly the formation of oxidation products in the oil analyzed. TG/DTG curves showed that 5-n-pentadecyl-2-tert-amylphenol is more stable than 2,6-di-t-butyl-4-methylphenol (BHT) when analyzed in different atmospheres: 143°C in air and nitrogen against 87°C in air for BHT.

Babassu (Attalea speciosa) is a typical oilseed from the Brazilian northeast that may be an alternative feedstock for biodiesel production. Generally, biodiesel is very susceptible to oxidation compared to mineral diesel, which represents a relevant disadvantage for storage and transportation. The presence of unsaturated compounds in biodiesel favors the initiation and propagation of oxidation reactions. In this study, the biodiesel samples were stabilized with three antioxidants: N,N′-disec-butyl-p-phenylenediamine (PDA), IONOL (a synthetic phenolic antioxidant), and unsaturated cardanol (a natural phenolic antioxidant). Then, the products were evaluated under accelerated conditions. The oxidation tests used the Rancimat method and the differential scanning calorimetry (DSC) method. The physicochemical properties of babassu biodiesel and its blends with the three antioxidants were within the limits of ASTM D6751. The results of accelerated experiments using the Rancimat method showed a significant improvement in the oxidative stability of the babassu biodiesel doped with PDA (>180 h) and IONOL (>55 h) for samples doped with 100 mg/kg. Using DSC, the thermal analysis enhanced the onset temperature of doped samples to 211.7 and 201.14 °C for PDA and IONOL, respectively. Doped samples with 100 mg/kg of unsaturated cardanol did not improve the oxidative stability of the pure babassu biodiesel sample. These results indicate a higher antioxidant activity of PDA when compared to the two phenolic antioxidants.

The present work shows the aspects related to the synthesis and thermogravimetric analysis of thiophosphorated and phosphorated compounds from hydrogenated cardanol. Studies on thermal-oxidative stability were investigated, using a classical thermoanalytical-thermogravimetric method (TG/DTG) in an air atmosphere. Its use as an antioxidant additive in hydrogenated naphthenic NH10, NH20 and NH140 oils was evaluated. The addition of 1.2% synthesized compounds to the oils has improved their thermal-oxidative stability by 5-15ºC. The occurrence of major thermal degradation events at higher temperatures (Tmax) in additivated oils is a good indication of the antioxidant properties of the thiophosphorated and phosphorated cardanol compounds antioxidant properties

Antianxiety drugs currently in use are associated with a number of serious side effects. Present study was designed to evaluate the efficacy of anacardic acids (AAs) isolated from cashew nut (Anacardium occidentale L.) shell liquid (CNSL) to treat anxiety as well as its role in oxidative stress in mice model. Anxiolytic effect of AA was evaluated using rota-rod and a set of behavioral tests in male Swiss albino mice at the doses of 10, 25, and 50 mg/kg. Flumazenil was used to evaluate the possible involvement of GABAergic system in the mechanism of action of AA. The effect of AA on oxidative stress in mice was evaluated by determining the concentration of malondialdehyde (MDA), reduced glutathione, and catalase (CAT) activity. The detection of DNA damage of the treated animals was performed using alkaline comet test in the hippocampus and frontal cortex of the animals. The results demonstrated that AA did not produce myorelaxant and sedative effects, nor did it cause a decrease in locomotor activity. The anxiolytic effect of AA was well-evident in all tests, especially at higher dose levels (25 and 50 mg/mg). Flumazenil reversed the anxiolytic effect of AA at all doses. In addition, AA reduced oxidative stress by decreasing the concentration of MDA and increasing the levels of reduced glutathione (GSH) and CAT activity. Statistical analysis by Pearson's correlation indicated a positive correlation between anxiolytic effect of AA to its antioxidant and lipid peroxidation inhibitory activity. Furthermore, increased CAT activity and GSH concentrations in the hippocampus and frontal cortex of mice was also complementary to the reduced genotoxic damage observed in the study. In comet assay, AA did not increase in DNA damage. In conclusion, the results supported that AA possesses GABA receptor mediated anxiolytic activity with the lack of myorelaxation and genotoxicity. © 2018 IUBMB Life, 70(5):420-431, 2018.