Diphenyl-1,4-phenylenediamine Research Articles

Recycled tire rubber materials in the spotlight. Determination of hazardous and lethal substances

One way of recycling end-of-life tires is by shredding them to obtain crumb rubber, a microplastic material (<0.5 mm), used as infill in artificial turf sports fields or as playground flooring. There is emerging concern about the health and environmental consequences that this type of surfaces can cause. This research aims to develop an analytical methodology able to determine 11 compounds of environmental and health concern, including antiozonants such as N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine (6PPD) or N, N´-diphenyl-1,4-phenylenediamine (DPPD), and vulcanization and crosslinking agents, such as N-cyclohexylbenzothiazole-2-sulfenamide (CBS), 1,3-di-o-tolylguanidine (DTG) or hexamethoxymethylmelamine (HMMM) from tire rubber. Ultrasound assisted extraction followed by liquid chromatography coupled to tandem mass spectrometry (UAE-LC-MS/MS) is validated demonstrating suitability. The methodology is applied to monitor the target compounds in forty real crumb rubber samples of different origin including, football pitches, outdoor and indoor playgrounds, urban pavements, commercial samples, and tires. Several alternative infill materials, such as sand, cork granulates, thermoplastic elastomers and coconut fibres, are also collected and analysed. All the target analytes are identified and quantified in the crumb rubber samples. The antiozonant 6PPD is present at the highest concentrations up to 0.2 % in new synthetic fields. The tire rubber-derived chemical 6PPD-quinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione), recently linked to acute mortality in salmons, is found in all types of crumb rubber samples attaining concentrations up to 40 μg g−1 in football pitches. The crosslinking agent HMMM is detected in most of the playing surfaces, at concentrations up to 36 μg g−1. The tested infill alternatives are free of most of the target compounds. To the best of our knowledge, this study is the largest study considering the target compounds in tire rubber particles and the first to focus on these compounds in playgrounds including the analysis of HMMM, 6PPD-quinone and DTG in crumb rubber used as an infill material.

Therapeutic effect of N, N-Diphenyl-1,4-phenylenediamine and adipose-derived stem cells coadministration on diabetic cardiomyopathy in type 1 diabetes mellitus-rat model.

Type 1 diabetes stem-cell-based treatment approach is among the leading therapeutic strategies for treating cardiac damage owing to the stem cells' regeneration capabilities. Mesenchymal stem cells derived from adipose tissue (AD-MSCs) have shown great potential in treating diabetic cardiomyopathy (DCM). Herein, we explored the antioxidant-supporting role of N, N'-diphenyl-1,4-phenylenediamine (DPPD) in enhancing the MSCs' therapeutic role in alleviating DCM complications in heart tissues of type 1 diabetic rats. Six male albinos Wistar rat groups have been designed into the control group, DPPD (250 mg/kg, i.p.) group, diabetic-untreated group, and three diabetic rat groups treated with either AD-MSCs (1 × 106 cell/rat, i.v.) or DPPD or both. Interestingly, all three treated diabetic groups exhibited a significant decrease in serum glucose, HbA1c, heart dysfunction markers (lactate dehydrogenase and CK-MP) levels, and lipid profile fractions (except for HDL-C), as well as some cardiac oxidative stress (OS) levels (MDA, AGEs, XO, and ROS). On the contrary, serum insulin, C-peptide, and various cardiac antioxidant levels (GSH, GST, CAT, SOD, TAC, and HO-1), beside viable cardiac cells (G0/G1%), were markedly elevated compared with the diabetic untreated group. In support of these findings, the histological assay reflected a marked enhancement in the cardiac tissues of all diabetic-treated groups, with obvious excellency of the AD-MSCs + DPPD diabetic-treated group. Such results strongly suggested the great therapeutic potentiality of either DPPD or AD-MSCs single injection in enhancing the cardiac function of diabetic rats, with a great noted enhancement superiority of DPPD and AD-MSCs coadministration.

N,N'-Diphenyl-1,4-phenylenediamine Antioxidant's Potential Role in Enhancing the Pancreatic Antioxidant, Immunomodulatory, and Anti-Apoptotic Therapeutic Capabilities of Adipose-Derived Stem Cells in Type I Diabetic Rats.

Mesenchymal stem cells (MSCs) are considered to be a promising therapeutic protocol for diabetes mellitus (DM) management. The latter is attributed to their differentiation potentiality to pancreatic β-cells, angiogenesis, and immune-modulatory capabilities by releasing various paracrine factors. Interestingly, antioxidant co-administration increased the MSCs' hypoglycemic and regenerative activities. Thus, this study aims to evaluate the therapeutic implication of type 1 DM after the co-administration of adipose tissue-derived-MSCs (AD-MSCs) and N,N'-d iphenyl-1,4-phenylenediamine (DPPD), compared to the single injection of either of them alone. In our four week long experiment, six rat groups were used as control, DPPD (250 mg/kg, i.p.), STZ-diabetic (D), D+DPPD, D+AD-MSCs (1 × 106 cell/rat, i.p.), and D+AD-MSCs+DPPD groups. Within this context, a single injection of AD-MSCs or DPPD into diabetic rats showed significant pancreatic anti-inflammatory, immunomodulation, antioxidant, and anti-apoptotic capacities, superior to AD-MSCs injection. However, AD-MSCs and DPPD co-administration into diabetic rats manifested the highest hypoglycemic and pancreatic regenerative activities in managing diabetes compared to the single shot of AD-MSCs or DPPD. These results highlight the synergetic role of DPPD as an antioxidant in enhancing AD-MSCs' therapeutic applications.

Protective Effect of DPPD on Mercury Chloride-Induced Hepatorenal Toxicity in Rats

Mercury is a global environmental pollutant, accumulating mainly in the kidney and liver inducing hepatorenal toxicity, oxidative stress, and tissue damage. Oxidative stress is caused by an imbalance between free radicals' production and cellular antioxidant defense systems. In the present study, we investigated the effect of N N′-diphenyl-1, 4-phenylenediamine (DPPD) antioxidant activity against mercury chloride- (HgCl2-) induced renal and hepatic toxicity. Thirty adult female Sprague Dawley rats were divided into three equal groups: the first group was injected with saline only and served as a control, the second group was injected with HgCl2, and the third group received DPPD + HgCl2 rats injected with HgCl2 without treatment showing a significant increase in alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, creatinine, and uric acids compared to control. Moreover, the second group showed a significant reduction in the activity of the antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH)) in addition to a marked increase in the malondialdehyde (MDA) content, histopathological alterations, collagen deposition, CD8%, CD4%, and TGF-β% in kidney and liver tissues compared with the control group. Treatment with DPPD showed significant recovery (p ≤ 0.001) in all previous parameters and histopathological examination. In conclusion, we suggested that DPPD may have a promising antioxidant capacity, gives it the applicability to be used as a prophylactic agent against mercury-induced hepatorenal cytotoxicity in the future.

Establishment of lower exhaust emissions by using EGR coupled low heat loss diesel engine with fuel blends of microalgae biodiesel-oxygenated additive DEE-antioxidant DPPD

The aims of the research work are: Achieving maximum reduction in the exhaust emissions of the diesel engine and investigate the potentiality of a higher ratio of biodiesel blended with suitable additives as an alternative for diesel fuel. Herein, a coated engine (CE) was produced by the application of bond coating NiCrAlY on the cylinder head and liner substrate, further it was coated with 8 mol.% Yttria-stabilized zirconia (8-YSZ) ceramic. The YSZ restrict the in-cylinder combustion heat loss to the coolant and combustion chamber components due to its low thermal conductivity. The CE was coupled with an exhaust gas recirculation (EGR) system at an optimal constant rate of 10% by vol. to reduce the formation of NOx emissions. Fuel blends with different combinations of microalgae (Chlorella protothecoides) oil-based biodiesel (MB) and additives diethyl ether (DEE), amine antioxidant N, N′-diphenyl-1,4-phenylenediamine (DPPD) were synthesized and tested. The experiment was carried out by scrutinizing the emissions and performance of CE fuelled by blends with a comparison to the uncoated engine (UE) with diesel at different load conditions. The results had shown that the additives enhanced the oxidation stability, cetane number while decreasing the viscosity of the biodiesel. The EGR coupled CE displayed improvement in all the investigated parameters with optimum of particulate emissions by 45.5%, un-burnt hydrocarbons by 51%, NOx by 18.5, CO emissions by 47%, peak brake thermal efficiency by about 6% and brake specific fuel consumption by 8.5% found for the blend MB85DEE15DPPD 1000 ppm (microalgae biodiesel 85%+ diethyl ether 15%+DPPD 1000 ppm) at 80% load. This work made a substantial approach to an economic contribution by simultaneously addressing global issues like air-pollution and fossil fuel crisis.

Mitigation of NOx emission using aromatic and phenolic antioxidant-treated biodiesel blends in a multi-cylinder diesel engine.

The present work analyzes the effect of antioxidants on engine combustion performance of a multi-cylinder diesel engine fueled with PB30 and PB50 (30 and 50 vol.% palm biodiesel (PB)). Four antioxidants namely N,N'-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-1,4-phenylenediamine (NPPD), 2(3)-tert-Butyl-4-methoxyphenol (BHA), and 2-tert-butylbenzene-1,4-diol (TBHQ) were added at concentrations of 1000 and 2000ppm to PB30 and PB50. TBHQ showed the highest activity in increasing oxidation stability in both PB30 and PB50 followed by BHA, DPPD, and NPPD respectively, without any negative effect on physical properties. Compared to diesel fuel, PB blends showed 4.61-6.45% lower brake power (BP), 5.90-8.69% higher brake specific fuel consumption (BSFC), 9.64-11.43% higher maximum in cylinder pressure, and 7.76-12.51% higher NO emissions. Carbon monoxide (CO), hydrocarbon (HC), and smoke opacity were reduced by 36.78-43.56%, 44.12-58.21%, and 42.59-63.94%, respectively, than diesel fuel. The start of combustion angles (SOC) of PB blends was - 13.2 to - 15.6 °CA BTDC, but the combustion delays were 5.4-7.8 °CA short compared to diesel fuel which were - 10 °CA BTDC and 11°CA respectively. Antioxidant fuels of PB showed higher BP (1.81-5.32%), CO (8.41-24.60%), and HC (13.51-37.35%) with lower BSFC (1.67-7.68%), NO (4.32-11.53%), maximum in cylinder pressure (2.33-4.91%) and peak heat release rates (HRR) (3.25-11.41%) than baseline fuel of PB. Similar SOC of - 13 to - 14 °CA BTDC was observed for PB blended fuels and antioxidants. It can be concluded that antioxidants' addition is effective in increasing the oxidation stability and in controlling the NOx emissions of palm biodiesel fuelled diesel engine.

Acid Doping of Phenyl-Capped Aniline Dimer: Intermolecular Polaron Formation Mechanism and Its Applicability to Polyaniline.

The acid doping process of the mixtures of N,N'-diphenyl-1,4-phenylenediamine (DPPD) and N,N'-diphenyl-1,4-quinonediimine (DPQD), reduced and oxidized phenyl-capped aniline dimers respectively, has been studied in detail by UV-vis-NIR and ESR spectroscopies. The addition of the acid to the mixtures of DPPD and DPQD leads to the formation of one type of radicals by intermolecular interactions. Full conversion of the aniline dimer molecules to the radical form is achievable only in stoichiometric mixtures of DPPD and DPQD. Concentration of radical species may change over time according to processes involving hydrolysis. The mechanisms of the acid doping of the phenyl-capped dimer process and subsequent side processes are proposed.

Reduction of amine and biological antioxidants on NOx emissions powered by mango seed biodiesel

This study scrutinizes the influence of amine and biological antioxidants on reduction of NOx emissions in a diesel engine fueled with B100 (100vol.% mango seed methyl ester) and B20 (20 vol.% mango seed methyl ester and 80 vol.% diesel fuel blend). Three amine antioxidants, p-phenylenediamine (PPD), Ethylendiamine (EDA) and N,N’-diphenyl- 1,4-phenylenediamine (DPPD) and three biological antioxidants, dichloromethane (DCM), alpha tocopherol acetate (α-T) and L-ascorbic acid (L-asc.acid) are tested in a kirloskar-make single cylinder four-stroke water cooled diesel engine of 5.9 KW rated power. There are five concentrations used in the antioxidant mixture of biodiesel blends. i.e., 0.005%-m, 0.010%-m, &nbsp;0.025%-m, 0.05%-m and 0.1%-m. Where, %-m is the molar concentration employed in the antioxidant mixture. Results show that consequential reduction in NOx could be acquired by the accession of antioxidant additive DPPD with the 0.025% concentration from B20 fuel by 15.4% and B100 fuel by 39%. The DPPD additive increased the CO emissions over 7.42% for B100 fuel and 6.44% for B20 fuel. The biological antioxidant DCM exhibits 0.235 g/kWhr for B100 fuel and 0.297 g/kWhr for B20 fuel. Smoke emission is found to have increased with the addition of antioxidants. Slight increase in brake thermal efficiency (0.91%) is accomplished with the addition of antioxidants at full load. The experimental results are compared with analysis of variance and the result is merely the same as to that of experimentation.

Performance and Emission Analysis of Rubber Seed Methyl Ester and Antioxidant in a Multicylinder Diesel Engine

In this study, the potential of using a nonedible biodiesel source (rubber seed oil) was explored. Rubber seed oil (RSO) is a promising nonedible source for producing a sustainable biodiesel in Malaysia. However, due to the lower oxidation stability of the produced biodiesel, which is the result of its higher unsaturation content (78.73%), an oxidation inhibitor is required. This paper examines the effect of antioxidants addition to rubber seed biodiesel (RB) on the combustion, engine performance, and emissions. Four antioxidants, namely, N,N′-diphenyl-1,4-phenylenediamine (DPPD), 2-tert-butylbenzene-1,4-diol (TBHQ), N-phenyl-1,4-phenylenediamine (NPPD), and 2(3)-tert-butyl-4-methoxyphenol (BHA), were added at concentrations of 1000 and 2000 ppm to 20% RB (RB20). The results showed that TBHQ had the greatest ability to increase the stability of RB20 followed by BHA, DPPD, and NPPD, respectively, without a significant effect on physical properties. The experiments were conducted in a 55 kW multicylinder di...

Effect of Antioxidants and Mesenchymal Stem Cells on Cisplatin Induced Renal Fibrosis in Rats

1.1.Background:Mesenchymal stem cells (MSCs) have generated a great deal of excitement and promise as a potential source of all types of cells for cell-based therapeutic strategies. The reparative role of MSCs may be multifunctional and include the secretion of anti-inflammatory cytokines like TGFβ1 to limit apoptosis and dampen the inflammatory response. There are reports suggesting that antioxidants such as N N'-diphenyl-1, 4-phenylenediamine (DPPD) inhibit interstitial fibrosis induced by cisplatin. It inhibits lipid peroxidation and nephrotoxicity induced by cisplatin, where antioxidants make trapping for free radicals. 1.2.Aim:We aimed to investigate the inhibitory potential of either stem cells or DPPD on renal fibrosis in cisplatin induced tubulointerstitial fibrosis rat model. 1.3.Materials and methods:This study was carried on 40 male Sprague-Dawley rats (body weight 170 - 220 g). Rats were divided into 4 groups as follow: Control group, received intravenous saline. Cisplatin group, received cisplatin (6 mg/kg, i.p). DPPD group, received cisplatin (6 mg/kg, i.p) at the start of experiments and three days after cisplatin administration, rats were given DPPD (0.5 g/kg, i.p) every two days. MSCs group, received cisplatin (6 mg/kg, i.p) at the start of experiments and three days after cisplatin administration, rats were given MSCs (1 ×106, i.v) single dose. 14 days after cisplatin (or saline) administration, blood samples were obtained and kidneys were removed for biochemical, histopathology and immunohistochemical markers investigations. 1.4.Results:In addition to the significant rise in urea and creatinine, cisplatin group showed atrophied glomeruli with tubular cells vacuolization and increased collagen deposition. Alpha smooth muscle actin (α-SMA) and fibroblast proliferation marker Ki-67 were found to be increased in renal tissue. Lipid peroxidation and collagen formation markers showed significant elevation. Both MSCs and antioxidant ameliorated cisplatin-induced nephrotoxicity to a great extent and showed marvelous anti-fibrotic effect as evidenced by histopathological, immunohistochemical and biochemical assessments. 1.5.Conclusion:Both MSCs and antioxidant (DPPD) were found to have potent potentials to inhibit tubulointerstitial fibrosis in cisplatin induced nephrotoxicity rat model.

Improving oxidation stability and NOX reduction of biodiesel blends using aromatic and synthetic antioxidant in a light duty diesel engine

Poor oxidation stability of biodiesel is now a major concern all over the world, especially due to its extensive utilisation in transport and industrialisation. Therefore, biodiesel needs better stability, in order to be sustainably utilised in the long term. The oxygen inhibitor antioxidant can counter the poor oxidation. In this experiment, 20% of Calophyllum inophyllum biodiesel (CIB20) was used as biodiesel feedstock. Three most effective antioxidants N, N′-diphenyl-1, 4-phenylenediamine (DPPD), N-phenyl-1, 4-phenylenediamine (NPPD) and 2-ethylhexyl nitrate (EHN) were used at a 1000ppm concentration with CIB20. The oxidation stability, exhaust emission and performance of a single cylinder diesel engine were analysed and compared to those of diesel. From the results, it was concluded that there was no significant negative impact on biodiesel physiochemical properties, while the stability of biodiesel (CIB20) with the addition of antioxidants with tested blends increased. Among these three antioxidants, DPPD exhibits a better stability in biodiesel. The results shows that CIB20 produced an average of 5.23% lower brake power (BP), 7.84% less brake thermal efficiency (BTE) and 11.2% higher brake specific fuel consumption (BSFC), compared to pure diesel. However, by mixing the antioxidant with CIB20, the BP and BTE, increased while the BSFC slightly decreased. For exhaust emission, antioxidants reduced NOx by about 5.92%–8.83%, with an increment of hydrocarbon (HC) and carbon-monoxide (CO) for all blends. For this reason, CIB20 blends with aromatic amine antioxidants can be used in diesel engine without any engine modifications.

Study of the oxidation stability and exhaust emission analysis of Moringa olifera biodiesel in a multi-cylinder diesel engine with aromatic amine antioxidants

In this study, the two most effective aromatic amine antioxidants N,N′-diphenyl-1,4-phenylenediamine (DPPD) and N-phenyl-1,4-phenylenediamine (NPPD), were used at a concentration of 2000 ppm. The impact of antioxidants on the oxidation stability, exhaust emission and engine performance of a multi-cylinder diesel engine fuelled with MB20 (20% Moringa oil methyl ester and 80% diesel fuel blend) were analysed at varying speed conditions at an interval of 500 rpm and a constant load. It was observed that, blending with diesel enhanced the oxidation stability of the moringa biodiesel by approximately 6.97 h, and the addition of DPPD and NPPD to MB20 increased the oxidation stability up to 34.5 and 18.4 h, respectively. The results also showed that the DPPD- and NPPD-treated blends reduced the NOx emission by 7.4% and 3.04%, respectively, compared to the untreated blend. However, they do have higher carbon monoxide (CO) and hydrocarbon (HC) levels and smoke opacities, but it should be noted that these emissions are still well below the diesel fuel emission level. The results show that the addition of antioxidant with MB20 also improves the engine's performance characteristics. Based on this study, MB20 blends with amine antioxidants can be used in diesel engines without any modification.

Flutamide-induced cytotoxicity and oxidative stress in an in vitro rat hepatocyte system.

Flutamide (FLU) is a competitive antagonist of the androgen receptor which has been reported to induce severe liver injury in some patients. Several experimental models suggested that an episode of inflammation during drug treatment predisposes animals to tissue injury. The molecular cytotoxic mechanisms of FLU in isolated rat hepatocytes using an in vitro oxidative stress inflammation system were investigated in this study. When a nontoxic hydrogen peroxide (H2O2) generating system (glucose/glucose oxidase) with peroxidase or iron(II) [Fe(II)] (to partly simulate in vivo inflammation) was added to the hepatocytes prior to the addition of FLU, increases in FLU-induced cytotoxicity and lipid peroxidation (LPO) were observed that were decreased by 6-N-propyl-2-thiouracil or deferoxamine, respectively. N-Acetylcysteine decreased FLU-induced cytotoxicity in this system. Potent antioxidants, for example, Trolox ((±)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), resveratrol (3,5,4′-trihydroxy-trans-stilbene), and DPPD (N,N′-diphenyl-1,4-phenylenediamine) also significantly decreased FLU-induced cytotoxicity and LPO and increased mitochondrial membrane potential (MMP) and glutathione (GSH) levels in the H2O2 generating system with peroxidase. TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a known reactive oxygen species (ROS) scavenger and superoxide dismutase mimetic, also significantly decreased toxicity caused by FLU in this system. These results raise the possibility that the presence or absence of inflammation may be another susceptibility factor for drug-induced hepatotoxicity.

Impacts of NOx reducing antioxidant additive on performance and emissions of a multi-cylinder diesel engine fueled with Jatropha biodiesel blends

Energy requirements are increasing rapidly due to fast industrialization and the increased number of vehicles on the road. The use of biodiesel in diesel engines instead of diesel results in the proven reduction of harmful exhaust emissions. However, most researchers have reported that they produce higher NOx emissions compared to diesel, which is a deterrent to the expansion of the market for these fuels. Several proposed pathways try to account for NOx formation during the combustion process. Among them, the Fenimore mechanism explains that fuel radicals formed during the combustion process react with nitrogen from the air to form NOx. It could be proposed that if these radical reactions could be terminated, the NOx formation rate for biodiesel combustion would decrease. An experimental study was conducted on a four-cylinder diesel engine to evaluate the performance and emission characteristics of Jatropha biodiesel blends (JB5, JB10, JB15 and JB20) with and without the addition of N,N′-diphenyl-1,4-phenylenediamine (DPPD) antioxidant. For each tested fuel, the engine performance and emissions were measured at engine speeds 1000–4000rpm at an interval of 500rpm under the full throttle condition. The results showed that this antioxidant additive could reduce NOx emissions significantly with a slight penalty in terms of engine power and Brake Specific Fuel Consumption (BSFC) as well as CO and HC emissions. However, when compared to diesel combustion, the emissions of HC and CO with the addition of the DPPD additive were found to be nearly the same or lower. By the addition of 0.15% (m) DPPD additive in JB5, JB10, JB15 and JB20, the reduction in NOx emissions were 8.03%, 3.503%, 13.65% and 16.54% respectively, compared to biodiesel blends without the additive under the full throttle condition. Moreover, the addition of DPPD additive to all biodiesel blend samples reduced the exhaust gas temperature.

Nanophase separated amphiphilic polymer co-networks as efficient matrices for optical sensors: Rapid and sensitive detection of NO2

A disposable and irreversible sensor for nitrogen dioxide detection, based on the reaction of NO2 with N,N′-diphenyl-1,4-phenylenediamine (DPPD) is described. This work focuses on the application of silicone-containing amphiphilic co-networks (APCNs) as immobilisation matrices for UV/VIS transmission spectroscopy for gas sensors. The developed flow-through gas sensor is based on a DPPD doped APCN, for real-time spectrophotometric detection of the oxidation product, and is formed in a 34μm thin film. The measurement principle presented here describes the NO2 concentration as a function of the temporal development of absorption at 450nm. A linear relationship between the change of absorption and the concentration of NO2 at different humidity is obtained in the range from 0.1 to 5.0ppm at ambient temperatures. As a consequence, the sensor response is reproducible with a very low detection threshold (20ppb) and detection times within seconds.

Effect of aromatic amine antioxidants on NOx emissions from a soybean biodiesel powered DI diesel engine

It is an overwhelming argument that the use of biodiesel instead of petrodiesel causes a reduction in harmful exhaust emissions from engines. A number of studies, however, indicate substantial increases in engine out NOx emissions with biodiesel fuel. Some studies have pointed out that the increased formation of prompt NOx is responsible for biodiesel NOx effect. Treatment of biodiesel with antioxidants is a promising approach because it reduces the formation of hydrocarbon free radicals, which are responsible for prompt NOx production in combustion process. Aromatic amine antioxidants are known as to be efficient inhibitors of free radicals. This study examines the use of p-phenylenediamine derived aromatic amine antioxidants for NOx reduction in a soybean biodiesel fuelled DI diesel engine. The antioxidant additives, N,N′-diphenyl-1,4-phenylenediamine (DPPD) and N-phenyl-1,4-phenylenediamine (NPPD) were tested on a computerised Kirloskar-make 4 stroke water cooled single cylinder diesel engine of 4.4kW rated power. Results show that significant reduction of NOx could be achieved by the addition of antioxidants but smoke, CO and HC emissions were found to have increased.

A variety of oxidation products of antioxidants based on N, N′-substituted p-phenylenediamines

Electrochemical and spectroscopic (EPR, UV–Vis, IR) studies of the aromatic secondary amines N, N′-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl- N′-isopropyl- p-phenylene diamine (IPPD), N-phenyl- N′-(α-methylbenzyl)- p-phenylenediamine (SPPD) and N-phenyl- N′-(1,3-dimethyl-butyl)- p-phenylenediamine (6PPD), which represent the most important group of antioxidants used in the rubber industry, are presented. During oxidation, all the compounds show reversible redox couples in acetonitrile/0.1 M TBABF 4. The first oxidation potential depends substantially on the R substituent at the –N′H– moiety. Very similar UV–VIS spectra of monocation radicals and dications for all the compounds were observed by applying anodic oxidation as well as oxidation by tert-butyl hydroperoxide both in air and in inert atmosphere. The samples with N′-bonded aliphatic carbon in the molecule (e.g. IPPD) heated in air undergo consecutive chemical reactions leading to the formation of –N′ C– group. By the use of RO 2 radicals only very low concentration of nitroxide radicals was obtained. Very high concentration of nitroxide radicals was achieved using 3-chloroperbenzoic acid. In the oxidation of investigated aromatic secondary amines with powder PbO 2 no EPR spectra were observed and UV–Vis and IR studies indicate the rapid formation of the final dehydrogenated oxidation product.

The Effect of Antioxidant on Development of Fibrosis by Cisplatin in Rats

Cisplatin causes chronic interstitial disease with fibrosis, but the development mechanism of interstitial fibrosis is not yet understood. We examined the effect of an antioxidant, N,N’-diphenyl-1,4-phenylenediamine (DPPD), on development of interstitial fibrosis induced by cisplatin. Cisplatin increased blood urea nitrogen (BUN), plasma creatinine, and elicited glucosuria and enzymuria at 3 days after administration, but these changes were restored to the normal level after 14 days. Type III collagen increased from 7 days after administration of cisplatin and the expansion of the interstitial fibrosis area became evident at 14 days. Sustained renal fibrosis worsened renal function again at 56 days. Administration of DPPD, which was started at 3 days after cisplatin treatment, significantly inhibited the increase in renal type III collagen contents and the expansion of the interstitial fibrosis area without affecting enzymuria and increased BUN. These results indicate that anti-fibrotic action of DPPD is not secondary due to the inhibition of acute renal injury but is rather a direct effect on renal fibrogenesis. DPPD did not prevent the infiltration of macrophages by cisplatin, suggesting that anti-fibrotic action of DPPD was not mediated by the inhibition of inflammatory cellular influx. It is suggested that reactive oxygen species are involved in cisplatin-induced renal interstitial fibrosis.

Determination of Ammonia Based on the Electrochemical Oxidation of N,N′-Diphenyl-1,4-phenylenediamine in Propylene Carbonate

The oxidation of N,N'-diphenyl-1,4-phenylenediamine (DPPD) has been studied by cyclic voltammetry at glassy carbon electrodes in propylene carbonate. Next, the reaction between ammonia and DPPD was similarly investigated. It has been shown that ammonia reversibly removes protons from oxidized DPPD molecules, thus facilitating the oxidative process with the emergence of a new wave at less positive potentials. The results suggest a novel methodology for the electrochemical determination of ammonia based on its interaction with DPPD in propylene carbonate. The measurement of the current of the new wave is shown to scale linearly with the ammonia concentration up to ca. 200 ppm and above.

Phenolic-rich juice prevents DNA single-strand breakage and cytotoxicity caused by tert-butylhydroperoxide in U937 cells: the role of iron chelation

The antioxidant potential of phenolic compounds is generally linked to their ability to scavenge free radicals. However, in addition to their radical-scavenging activity, phenolic compounds can chelate metal ions, such as iron, to prevent their participation in Fenton-type reactions, which lead to the formation of free radicals. The aim of the present study was to evaluate the ability of a phenolic-rich juice made from grapes, cherries and berries to protect human myeloid leukemia (U937) cells from oxidative stress caused by tert-butylhydroperoxide (tB-OOH). Preincubation of cells with extracts of the phenolic-rich juice at different concentrations (0–200 μM ferulic acid equivalents) for 3 h partially prevented cell death and abolished the DNA cleavage induced by tB-OOH. Moreover, when preincubating cells with the 100-μM juice extract (the dose that diminished cell death by around 50%), the partial prevention of tB-OOH-induced formation of reactive oxygen species (ROS) and mitochondrial permeability transition pore opening was observed. The radical scavenger antioxidant N, N′-diphenyl-1,4-phenylene-diamine (DPPD) and the intracellular iron chelator o-phenanthroline ( o-Phe) were also tested to know whether protective effects depended on radical-scavenging or iron-chelating activities. o-Phe prevented cell death, DNA cleavage and ROS generation, whereas DPPD only prevented cell death, suggesting that phenolics in the juice afforded protection against induced oxidative stress, most probably by means of an iron-chelating mechanism.