Butylated hydroxytoluene (BHT) is one of the most frequently used synthetic phenolic antioxidants added to food and consumer products such as plastics as a preservative. Due to its high production volume, BHT has been detected in aquatic environments, raising concerns about sub-lethal toxicity. However, there are limited toxicological data for BHT, especially in fish. In this study, zebrafish embryos were exposed to BHT at concentrations ranging 0.01–100 μM for up to 6 days post fertilization (dpf). Acute toxicity was assessed, and experiments revealed that BHT had a 96 h LC50 value of 57.61 μM. At sub-lethal doses (0.1–60 μM), BHT markedly decreased heart rates of zebrafish embryos at 48 h and 72 h by ∼25–30%. Basal and maximal respiration of zebrafish embryos at 24 hpf were decreased by 59.3% and 41.4% respectively following exposure to 100 μM BHT. Behavior in zebrafish was measured at 6 dpf following exposures to 0.01–10 μM BHT. Locomotor behaviors (e.g. total distance moved and velocity) were significantly increased in larvae at doses higher than 0.1 μM BHT. In addition, dark-avoidance behavior was decreased following exposure to 0.01 μM BHT, while conversely, it was increased in zebrafish exposed to 0.1 μM BHT. To investigate potential underlying mechanisms that could explain behavioral changes, transcripts involved in dopamine signaling were measured. Relative expression of dat mRNA was increased in larval fish from the 0.01 μM BHT treatment, while there were no effects on dat mRNA levels at higher concentrations. The mRNA levels of drd3 were decreased in zebrafish from the 1 μM BHT treatment. Taken together, BHT can affect the expression of the dopamine system, which is hypothesized to be related to the abnormal anxiety-associated behavior of larval zebrafish.

Synthetic phenolic antioxidants (SPAs) have received increasing attention due to the reports of toxicity and environmental contamination. Nevertheless, limited information was available on human burdens of these SPAs, with the exception of 2,6-di-tert-butyl-4-methylphenol (BHT). In our study, BHT as well as six other SPAs were analyzed in human urine samples from United States donors. Three SPA congeners were detected in human urine: BHT, 2,4-di-tert-butylphenol (DBP), and 3-tert-butyl-4-hydroxyanisole (BHA). BHT, which is the congener received most concerns, was detected at low concentrations [geometric mean (GM): 0.06 ng/mL], whereas four of its metabolites were detected at relatively high concentrations (GM: 1.68 ng/mL). Surprisingly, DBP was detected at extremely high concentrations (GM: 18.3 ng/mL). The concentrations of DBP (GM: 25.8 ng/mL), BHT (0.853 ng/mL), and metabolites (GM: 10.5 ng/mL) increased significantly after the urine samples were hydrolyzed by β-glucuronidase (p < 0.01), indicating the prevalence of the conjugated forms of SPAs and their metabolites in human urine. DBP, which has previously received little attention, was the predominant congener, contributing 88.2% and 63.6% to total target concentrations in the urine samples before and after β-glucuronidase hydrolysis, respectively. Thus, previous studies have vastly underestimated the burdens of SPAs to humans. To our knowledge, this is the first study revealing the presence of DBP in human urine.

In this study, seven synthetic phenolic antioxidant (SPA) analogues were positively found in urban and rural indoor dust samples collected from Shandong province in China, among which the novel 2,4,6-tri-tert-butylphenol (AO 246), 2,6-di-tert-butyl-4-sec-butylphenol (DTBSBP), 2,4-di-tert-butylphenol (DBP) and 4,4'-butylidenebis (2-(1,1-dimethylethyl)-5- methyl-phenol) (AO 44B25) analogues accounted for 29% of total SPA concentrations (∑SPAs). Urban dust showed significantly higher ∑SPA levels (range: 1.56e3 - 2.03e4 ng/g) compared with those in rural indoor dust (668–4.39e3 ng/g, p < 0.05). 2,6-Di-tert-butyl-4-methylphenol (BHT) was the dominate analogue in the urban indoor dust, which constituted of 74% in ΣSPAs. While, varied composition profiles of SPAs were noticed in rural indoor dust, for instance, AO 246 (46%) and BHT (43%) had similar contributions to ∑SPAs. Three BHT transformation products (TPs) were also detected in most of the urban and rural dust samples (>97%), with individual residue level in the same order: 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q) > 2,6-di-tert-butyl-4-hydroxy- 4-methyl-2,5-cyclo-hexadienone (BHT-quinol) > 3,5-di-tert-butyl-4-hydroxybenzal-dehyde (BHT-CHO). Geometric mean values of total TP concentrations were 555 ng/g and 131 ng/g for urban and rural indoor dust samples, respectively. A preliminary estimated daily intake calculation at dust ingestion scenario suggested additional concerns might be paid to simultaneous exposure of several SPA analogues and TPs besides current focus on BHT exposure risks.

Butylated hydroxytoluene (BHT) is a synthetic phenolic antioxidant that has been used as an additive for fat- or oil-containing foods. The exposure index value increases with extended usage of the chemical. Further, estimated total amount of BHT could exceed standard regulation, considering dietary intake or another exposure. Although BHT may induce side effects in reproductive systems, adequate research had not yet been performed to confirm them. In this study, we investigated the effects of BHT on mouse Leydig cells (TM3), which are components of testis. Our results indicated that BHT suppressed cellular proliferation and induced cell cycle arrest in TM3 cells. Moreover, BHT hampered cytosolic and mitochondrial calcium homeostasis in TM3 cells. Furthermore, BHT treatment led to endoplasmic reticulum (ER) stress and DNA fragmentation, simultaneously stimulating intrinsic apoptosis signal transduction. To elucidate the mode of action of BHT on Leydig cells, we performed western blot analysis and confirmed the activation of the PI3K/AKT and MAPK pathways. Collectively, our results demonstrated that BHT has toxic effects on mouse Leydig cells via induction of calcium dysregulation and ER-mitochondria dysfunction.

Butylated hydroxytoluene (BHT), one of the most widely used synthetic phenolic antioxidants, is a popular food additive. Previous studies have reported the possible health hazards of BHT. However, BHT effects on female reproduction, especially on endometrial decidualization, are still unknown. During early pregnancy, decidualization plays important roles for embryo implantation and pregnancy establishment. This study aimed to explore the effects of BHT on endometrial decidualization in pregnant mice. The pregnant mice received BHT via intraperitoneal injection at doses of 0, 200, and 400 mg/kg/day from day 1 (D1) of pregnancy until sacrifice. Under BHT exposure, maternal body weight was significantly decreased during early pregnancy. Compared with the control group, the number of implantation sites and uterine weight were significantly reduced in the BHT groups. The uterine lumen failed to close after BHT exposure, and the decidual morphology of endometrial stromal cells was inhibited by BHT. Furthermore, BHT significantly decreased the expression of endometrial decidual markers including COX2, HOXA10, and MMP9. Notably, the levels of serum estrogen (E2) and progesterone (P4) and expression levels of uterus estrogen receptor α (ERα) and progesterone receptor (PR) during early pregnancy were significantly upregulated following BHT exposure. In conclusion, these results demonstrated that gestational BHT exposure could inhibit decidualization of mouse endometrium during early pregnancy. The disorders of reproductive hormones and changes of hormone receptor signals could be responsible for the impaired decidualization. This study provided new evidence for the deleterious effects of BHT on female reproduction and revealed the potential reproductive toxicity of synthetic phenolic antioxidants.

The present study presented an inclusive analysis of engine exhaust emission characteristics of direct injection diesel engine fuelled with diesel and biofuel. Biofuel used in this investigation was obtained by steam distillation from pine oil. A single-cylinder, four-stroke diesel engine was used for this purpose. In this work, performance characteristics like brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC) were analysed. The engine pollutants, namely nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke, were examined. In addition, combustion characteristics like in-cylinder pressure and heat release rate were presented. Two engine modification techniques, namely thermal barrier coating and the addition of antioxidant to biofuel, were attempted. The advantage of thermal barrier coating is to reduce heat loss from the engine and convert the accumulated heat into useful piston work. In this work, partially stabilised zirconia was used as the coating material. The usage of antioxidant-treated biofuel in a diesel engine was said to be the prominent approach for NOx emission reduction. Three different antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ), were exclusively dissolved at a concentration of 1% by volume with PO fuel. The obtained performance and emission characteristics of the uncoated engine were compared with the thermally coated engine. From the results, it was observed that the PO biofuel may be a promising alternative in the near prospect with the thermal barrier coating technique to enhance the performance, combustion and emission characteristics of diesel engine. The PO+TBHQ blend was considered as more beneficial than PO+BHT and PO+BHA on account of its performance, combustion and emission characteristics. The effectiveness of the antioxidant was shown in the order of TBHQ>BHA>BHT.

The study represents a comprehensive analysis of engine exhaust emission variation from a compression ignition (CI) diesel engine fueled with diesel-biodiesel blends. Biodiesel used in this investigation was produced through transesterification procedure from Moringa oleifera oil. A single cylinder, four-stroke, water-cooled, naturally aspirated diesel engine was used for this purpose. The pollutants from the exhaust of the engine that are monitored in this study are nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke opacity. Engine combustion and performance parameters are also measured together with exhaust emission data. Some researchers have reported that the reason for higher NO emission of biodiesel is higher prompt NO formation. The use of antioxidant-treated biodiesel in a diesel engine is a promising approach because antioxidants reduce the formation of free radicals, which are responsible for the formation of prompt NO during combustion. Two different antioxidant additives namely 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol) (MBEBP) were individually dissolved at a concentration of 1% by volume in MB30 (30% moringa biodiesel with 70% diesel) fuel blend to investigate and compare NO as well as other emissions. The result shows that both antioxidants reduced NO emission significantly; however, HC, CO, and smoke were found slightly higher compared to pure biodiesel blends, but not more than the baseline fuel diesel. The result also shows that both antioxidants were quite effective in reducing peak heat release rate (HRR) and brake-specific fuel consumption (BSFC) as well as improving brake thermal efficiency (BTE) and oxidation stability. Based on this study, antioxidant-treated M. oleifera biodiesel blend (MB30) can be used as a very promising alternative source of fuel in diesel engine without any modifications.

This manuscript presents the impact of addition of antioxidant additives to rice bran biodiesel blend on the performance and emission characteristics of compression ignition (C.I) engine. Rice bran methyl ester (RBME) was produced from rice bran oil by transesterification using sodium hydroxide as catalyst. An experimental investigation was conducted on a single-cylinder four-stroke C.I engine to analyze the performance and emission characteristics of rice bran methyl ester (RBME) blended with diesel at 20% by volume (B20) with and without addition of 1000 ppm of two monophenolic antioxidant additives, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The results showed that the BHA- and BHT-treated B20 blend decreased the brake specific fuel consumption (BSFC) by 2.1 and 1.2% and increased the brake thermal efficiency (BTE) by 1.04 and 0.5% compared to B20. The BHA- and BHT-treated B20 blend produced mean reductions in NOx emission of 12.2 and 9.6%, respectively, compared to B20. The carbon monoxide (CO) and hydrocarbon (HC) emissions of BHA- and BHT-treated B20 were increased by 14.8–16.6% and 10.6–11.2%, respectively, compared to B20. However the emission levels were lower than those of diesel.

The aim of this study was to evaluate and compare the antioxidant potential of essential oils of some commonly used Indian spices (black pepper, cinnamon, clove, coriander and cumin) in various in vitro models and in food supplements enriched with omega-6 and omega-3 fatty acids. In vitro antioxidant potential was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging and Fe²⁺ ion-chelating methods and lipid oxidation stabilisation potential was evaluated in bulk soybean oil-fish oil mixture and their oil-in-water emulsions using peroxide value (PV), p-anisidine value (p-AV) and total oxidation value as indicators of oxidation. Combination effects using DPPH radical scavenging and Briggs-Rauscher oscillating reaction methods were also evaluated. Test essential oils showed varying degrees of radical scavenging and Fe²⁺ ion-chelating efficacy. Clove and coriander oils showed significantly higher (P < 0.05) radical scavenging and Fe²⁺ ion-chelating potential over other tested essential oils as well as BHT and ∞-tocopherol. The anti-lipid peroxidative potential of test essential oils was found in the following decreasing order: clove > coriander > BHT > cinnamon > α-tocopherol > cumin > black pepper. Furthermore, clove and coriander oils showed synergistic antioxidant activity in combination both in DPPH radical scavenging and Briggs-Rauscher oscillating reaction methods whereas other possible combinations showed additive effects. Strong radical scavenging and Fe²⁺-chelating as well as anti-lipid peroxidative activities of clove and coriander oils provide evidence that clove and coriander oils may serve as a potential source of natural antioxidants for retarding lipid oxidation of food supplements enriched with omega-6 and omega-3 fatty acids.