Exploring the dual effect of novel 1,4-diarylpyranopyrazoles as antiviral and anti-inflammatory for the management of SARS-CoV-2 and associated inflammatory symptoms.

COVID-19 and associated substantial inflammations continue to threaten humankind triggering death worldwide. So, the development of new effective antiviral and anti-inflammatory medications is a major scientific goal. Pyranopyrazoles have occupied a crucial position in medicinal chemistry because of their biological importance. Here, we report the design and synthesis of a series of sixteen pyranopyrazole derivatives substituted with two aryl groups at N-1 and C-4. The designed compounds are suggested to show dual activity to combat the emerging Coronaviruses and associated substantial inflammations. All compounds were evaluated for their in vitro antiviral activity and cytotoxicity against SARS-CoV infected Vero cells. As well, the in vitro assay of all derivatives against the SARS-CoV Mpro target was performed. Results revealed the potential of three pyranopyrazoles (22, 27, and 31) to potently inhibit the viral main protease with IC50 values of 2.01, 1.83, and 4.60 µM respectively compared with 12.85 and 82.17 µM for GC-376 and lopinavir. Additionally, in vivo anti-inflammatory testing for the most active compound 27 proved its ability to reduce levels of two cytokines (TNF-α and IL-6). Molecular docking and dynamics simulation revealed consistent results with the in vitro enzymatic assay and indicated the stability of the putative complex of 27 with SARS-CoV-2 Mpro. The assessment of metabolic stability and physicochemical properties of 27 have also been conducted. This investigation identified a set of metabolically stable pyranopyrazoles as effective anti-SARS-CoV-2 Mpro and suppressors of host cell cytokine release. We believe that the new compounds deserve further chemical optimization and evaluation for COVID-19 treatment.

Targeted potent antimicrobial benzochromene-based analogues: Synthesis, computational studies, and inhibitory effect against 14α-Demethylase and DNA Gyrase.

7H-Benzo[7,8]chromeno[2,3-d]pyrimidin-9(8H)-amine (6a,b) have been synthesized via hydrazinolysis of the imidates (5a,b). Polysubstituted chromenotriazolopyrimidine (7a-j), (12a,b) and Schiff base (8a,b) derivatives have also been prepared. The new heterocyclic derivatives were affirmed by spectral data. The target compounds have been screened for antibacterial and antifungal activity. Compounds 6a,b and 7a-c, g,h displayed the most favorable antimicrobial activities in resemblance to the reference antimicrobial agents by IZ range over 24 mm. In addition, MIC, MBC and MFC were also tested and screen for most active compound 6a by 6.25 µg/mL showing bactericidal effect. SAR study revealed that the antimicrobial vitality of the target compounds was safely influenced by the lipophilicity substituents and the calculated log P value. The potent compounds were subjected into in vitro enzyme screening (14α-Demethylase and DNA Gyrase) against both interesting targets and showed good inhibitory profile. Molecular modeling analyses were introduced and discussed focusing on the docking of active compounds into two essential targets, and their ADMET properties were studied.

Generation of Combinatorial Lentiviral Vectors Expressing Multiple Anti-Hepatitis C Virus shRNAs and Their Validation on a Novel HCV Replicon Double Reporter Cell Line.

Despite the introduction of directly acting antivirals (DAAs), for the treatment of hepatitis C virus (HCV) infection, their cost, patient compliance, and viral resistance are still important issues to be considered. Here, we describe the generation of a novel JFH1-based HCV subgenomic replicon double reporter cell line suitable for testing different antiviral drugs and therapeutic interventions. This cells line allowed a rapid and accurate quantification of cell growth/viability and HCV RNA replication, thus discriminating specific from unspecific antiviral effects caused by DAAs or cytotoxic compounds, respectively. By correlating cell number and virus replication, we could confirm the inhibitory effect on the latter of cell over confluency and characterize an array of lentiviral vectors expressing single, double, or triple cassettes containing different combinations of short hairpin (sh)RNAs, targeting both highly conserved viral genome sequences and cellular factors crucial for HCV replication. While all vectors were effective in reducing HCV replication, the ones targeting viral sequences displayed a stronger antiviral effect, without significant cytopathic effects. Such combinatorial platforms as well as the developed double reporter cell line might find application both in setting-up anti-HCV gene therapy approaches and in studies aimed at further dissecting the viral biology/pathogenesis of infection.

Modulatory effects of perindopril on cisplatin-induced nephrotoxicity in mice: Implication of inflammatory cytokines and caspase-3 mediated apoptosis.

Cisplatin-induced nephrotoxicity limits its anticancer effectiveness, thus this study's aim was to assess the potential modulatory effect of perindopril on cisplatin-induced nephrotoxicity and to elucidate the possible underlying mechanisms. Renal dysfunction was induced in mice by a single injection of cisplatin (10 mg kg-1, i.p.) and perindopril was administered orally (2 mg kg-1, once daily) for 5 days. Perindopril remarkably ameliorated cisplatin-induced perturbations in renal histology, renal levels of tumor necrosis factor-alpha, interleukin-6 and interleukin-10, apoptosis-regulating protein expressions (Bax and Bcl2), and partially normalized Bax to Bcl2 ratio and active caspase 3 protein expression. Conversely, perindopril had no significant effect on cisplatin-induced elevations in serum creatinine and urea, microalbuminuria, kidney to body weight ratio, lipid peroxidation marker, superoxide dismutase and catalase activities and reduced glutathione content. In conclusion, perindopril may be safely used with cisplatin in mice since it ameliorated cisplatin-induced histopathological changes, inflammation and apoptosis without affecting renal biomarkers or oxidative stress.

Aspernolide F, as a new cardioprotective butyrolactone against doxorubicin-induced cardiotoxicity.

Endophytic fungi have known as a promising source of secondary metabolites. γ-Butyrolactones are a class of metabolites reported from Aspergillus genus, which attracted much attention for their bioactivities. This study aimed to assess the potential cardioprotective effects of aspernolide F (AF) separated from the endophytic fungus A. terreus against doxorubicin (DOX)-induced cardiotoxic effects in rats. Animals were treated with two different doses of AF for 10 days prior to DOX injection. Electrocardiographic (ECG), biochemical, histopathological and immunohistochemical analyses were performed. Results have shown that AF effectively protected against DOX-induced cardiac damage as AF counteracted DOX-induced ECG abnormalities and attenuated serum markers of cardiotoxicity (creatine kinase-MB, lactate dehydrogenase, troponin I, and troponin T). Histopathological examination of cardiac tissue revealed a remarkable improvement in DOX-induced lesions. In addition, AF ameliorated DOX-induced oxidative damage and increased the levels of antioxidants in cardiac tissues. AF treatment inhibited the activation of nuclear factor-κB (NF-κB) and decreased the immuno-expression of NF-κB in cardiac tissue. Furthermore, AF caused a marked lowering in the level of inflammatory cytokines (nitric oxide, tumor necrosis factor-α, and interleukin-6) in the cardiac tissue. Collectively, this study demonstrates the cardioprotective activity of AF against DOX-induced cardiac damage which may be due to its antioxidant and anti-inflammatory activities.

Isoniazid induces a monocytic-like phenotype in HL-60 cells.

Isoniazid (INH) is one of the oldest drugs for the treatment of tuberculosis (TB) and is of continual clinical and research interest. The aim of the current study is to investigate the ability of INH to induce monocyte differentiation and the underlying signaling pathway involved in this phenomenon using HL-60 cells. In this study, HL-60 cells were treated with different non-cytotoxic concentrations of INH or vitamin D (a well-known inducer of monocytic differentiation) to determine key functional changes in the phenotype of these cells using several biochemical and cytobiological experiments. HL-60 cells are derived from human promyelocytic leukemia and bear some resemblance to promyelocytes, which differentiate into various cell types. INH-induced differentiation was confirmed to occur in a concentration-dependent manner through several functional markers such as nonspecific esterase activity, NADPH oxidase activity and expression of surface markers CD14 and CD16 (characteristic of monocytes). INH-induced monocytic-like differentiation in HL-60 cells and demonstrated that at least 25% of cells were differentiated within the range of the pharmacological concentrations of INH. To determine the effects of INH on HL-60 cells, we applied quantitative proteomics that revealed 32 proteins were altered significantly in pathways that could involve differentiation signals. Lastly, INH activated the ERK-1/MAPK signaling pathway based on detection of phosphorylated ERK-1. These in vitro findings in HL-60 cells warrant further study using promyelocytes or hematopoietic stem cells to evaluate the physiological capability of INH to induce monocytic differentiation that may aid in host defense against TB.

Protective effects of Ajwa date extract against tissue damage induced by acute diclofenac toxicity.

OBJECTIVES: To investigate the tissue-protective effects of Ajwa date fruits (a Prophetic medicinal remedy) against acute diclofenac toxicity. METHODS: Albino Sprague-Dawley rats were allocated to four experimental groups: a negative control group, an Ajwa-only group that received 2 g/kg of Ajwa date extract (ADE) orally, an acute diclofenac toxicity group that received 200 mg diclofenac once intraperitoneally, and a treatment group that received diclofenac and ADE after 4 h. Histological examinations of rat lung and liver tissues were performed. RESULTS: Acute diclofenac toxicity caused marked hepatic derangements, such as congested central veins, congested blood sinusoids, hyaline degeneration, and hepatocyte necrosis. Toxic diclofenac overdose resulted in markedly congested alveolar capillaries and alveolar haemorrhages, thick edematous alveolar walls, and edema fluid exudates in the alveoli. Upon treatment with ADE, significant reduction in diclofenac-induced hepatic and pulmonary derangements were observed. CONCLUSION: ADE is a safe, tissue-protective nutritional agent that alleviates cellular and tissue-damaging effects due to acute diclofenac toxicity. ADE relieved hepatic and pulmonary changes induced by acute diclofenac toxicity. The use of ADE is recommended for the treatment of acute diclofenac toxicity.

Agmatine protects against sodium valproate-induced hepatic injury in mice via modulation of nuclear factor-κB/inducible nitric oxide synthetase pathway.

Valproate is a widely used drug against epilepsy and several other neurological disorders although it has deleterious hepatotoxic side effects. The current study was designed to test if agmatine as nitric oxide modulator has protective effects against valproate-induced hepatic injury. Male Swiss albino mice were treated with sodium valproate (SVP) with or without agmatine for 7 days. Serum and liver samples were collected for analysis. Results have revealed that agmatine exerted hepatoprotective effects against SVP-associated hepatic injury. Agmatine ameliorated SVP-induced elevated serum biochemical markers of hepatic damage such as serum transaminases, alkaline phosphatase, γ-glutamyl transferase, and lactate dehydrogenase. Histopathological examination of the liver showed improvement of hepatic lesions in case of agmatine treatment. Furthermore, agmatine attenuated oxidative stress and enhanced antioxidants in liver tissue. Agmatine inhibited the activation of nuclear factor-κB and ameliorated the immunoexpression of inducible nitric oxide synthetase. This was accompanied by decrease in the level of inflammatory markers as nitrite/nitrate, tumor necrosis factor-α, and interleukin-6. These data provide new evidence of the hepatoprotective activity of agmatine against SVP-induced hepatotoxic effects.

Characterization of Mechanisms of Glutathione Conjugation with Halobenzoquinones in Solution and HepG2 Cells.

Halobenzoquinones (HBQs) are a class of emerging disinfection byproducts. Chronic exposure to chlorinated drinking water is potentially associated with an increased risk of human bladder cancer. HBQ-induced cytotoxicity involves depletion of cellular glutathione (GSH), but the underlying mechanism remains unclear. Here we used ultrahigh performance liquid chromatography-high resolution mass spectrometry and electron paramagnetic resonance spectroscopy to study interactions between HBQs and GSH and found that HBQs can directly react with GSH, forming various glutathionyl conjugates (HBQ-SG) in both aqueous solution and HepG2 cells. We found that the formation of HBQ-SG varies with the initial molar ratio of GSH to HBQ in reaction mixtures. Higher molar ratios of GSH to HBQ facilitate the conjugation of more GSH molecules to an HBQ molecule. We deduced the reaction mechanism between GSH and HBQs, which involves redox cycling-induced formation of halosemiquinone (HSQ) free radicals and glutathione disulfide, Michael addition, as well as nucleophilic substitution. The proposed reaction rates are in the following order: formation of HSQ radicals > substitution of bromine by GSH > Michael addition of GSH on the benzoquinone ring > substitution of chlorine by GSH > substitution of the methyl group by GSH. The conjugates identified in HBQ-treated HepG2 cells were the same as those found in aqueous solution containing a 5:1 ratio of GSH:HBQs.

Anti-inflammatory and antioxidant properties of a novel resveratrol-salicylate hybrid analog.

Resveratrol is a natural compound with a plethora of activities as well as limitations. We recently reported a series of resveratrol-salicylate analogs with potential chemopreventive activity. Herein, we report the anti-inflammatory and antioxidant properties of these resveratrol derivatives. Using an in vitro COX inhibition assay, and two in vivo protocols (carrageenan-induced peritonitis and paw edema), we identified a novel compound (C10) as a potent anti-inflammatory agent. The enhanced potency of C10 was associated with the ability of C10 to decrease the activity of myeloperoxidase (MPO) enzyme at 10mg/kg, whereas resveratrol and it's natural analog (TMS) did not exert the same effect. Additionally, C10 significantly reduced the concentration of intracellular reactive oxygen species. Because of the proven association between cancer, inflammation, and oxidative stress, we believe that C10 is a promising chemopreventive molecule.

Metabolism of isoniazid by neutrophil myeloperoxidase leads to isoniazid-NAD(+) adduct formation: A comparison of the reactivity of isoniazid with its known human metabolites.

The formation of isonicotinyl-nicotinamide adenine dinucleotide (INH-NAD(+)) via the mycobacterial catalase-peroxidase enzyme, KatG, has been described as the major component of the mode of action of isoniazid (INH). However, there are numerous human peroxidases that may catalyze this reaction. The role of neutrophil myeloperoxidase (MPO) in INH-NAD(+) adduct formation has never been explored; this is important, as neutrophils are recruited at the site of tuberculosis infection (granuloma) through infected macrophages' cell death signals. In our studies, we showed that neutrophil MPO is capable of INH metabolism using electron paramagnetic resonance (EPR) spin-trapping and UV-Vis spectroscopy. MPO or activated human neutrophils (by phorbol myristate acetate) catalyzed the oxidation of INH and formed several free radical intermediates; the inclusion of superoxide dismutase revealed a carbon-centered radical which is considered to be the reactive metabolite that binds with NAD(+). Other human metabolites, including N-acetyl-INH, N-acetylhydrazine, and hydrazine did not show formation of carbon-centered radicals, and either produced no detectable free radicals, N-centered free radicals, or superoxide, respectively. A comparison of these free radical products indicated that only the carbon-centered radical from INH is reducing in nature, based on UV-Vis measurement of nitroblue tetrazolium reduction. Furthermore, only INH oxidation by MPO led to a new product (λmax=326nm) in the presence of NAD(+). This adduct was confirmed to be isonicotinyl-NAD(+) using LC-MS analysis where the intact adduct was detected (m/z=769). The findings of this study suggest that neutrophil MPO may also play a role in INH pharmacological activity.

Cytoprotective effect of isoniazid against H2O2 derived injury in HL-60 cells.

To combat tuberculosis (TB), host phagocytic cells need to survive against self-generating oxidative stress-induced necrosis. However, the effect of isoniazid (INH) in protecting cells from oxidative stress-induced necrosis has not been previously investigated. In this in vitro study, the cytotoxic effect of H2O2 generation using glucose oxidase (a model of oxidative stress) was found to be abrogated by INH in a concentration-dependent manner in HL-60 cells (a human promyelocytic leukemia cell). In cells treated with glucose oxidase, both ATP and mitochondrial membrane potential were found to be decreased. However, treatment with INH demonstrated small but significant attenuation in decreasing ATP levels, and complete reversal for the decrease in mitochondrial membrane potential. Quantitative proteomics analysis identified up-regulation of 15 proteins and down-regulation of 14 proteins which all together suggest that these proteomic changes signal for increasing cellular replication, structural integrity, ATP synthesis, and inhibiting cell death. In addition, studies demonstrated that myeloperoxidase (MPO) was involved in catalyzing INH-protein adduct formation. Unexpectedly, these covalent protein adducts were correlated with INH-induced cytoprotection in HL-60 cells. Further studies are needed to determine whether the INH-protein adducts were causative in the mechanism of cytoprotection.

Proteomic profile of aminoglutethimide-induced apoptosis in HL-60 cells: Role of myeloperoxidase and arylamine free radicals.

In this study, the cellular effects resulting from the metabolism of aminoglutethimide by myeloperoxidase were investigated. Human promyelocytic leukemia (HL-60) cells were treated with aminoglutethimide (AG), an arylamine drug that has a risk of adverse drug reactions, including drug-induced agranulocytosis. HL-60 cells contain abundant amounts of myeloperoxidase (MPO), a hemoprotein, which catalyzes one-electron oxidation of arylamines using H2O2 as a cofactor. Previous studies have shown that arylamine metabolism by MPO results in protein radical formation. The purpose of this study was to determine if pathways associated with a toxic response could be determined from conditions that produced protein radicals. Conditions for AG-induced protein radical formation (with minimal cytotoxicity) were optimized, and these conditions were used to carry out proteomic studies. We identified 43 proteins that were changed significantly upon AG treatment among which 18 were up-regulated and 25 were down-regulated. The quantitative proteomic data showed that AG peroxidative metabolism led to the down-regulation of critical anti-apoptotic proteins responsible for inhibiting the release of pro-apoptotic factors from the mitochondria as well as cytoskeletal proteins such as nuclear lamina. This overall pro-apoptotic response was confirmed with flow cytometry which demonstrated apoptosis to be the main mode of cell death, and this was attenuated by MPO inhibition. This response correlated with the intensity of AG-induced protein radical formation in HL-60 cells, which may play a role in cell death signaling mechanisms.

Phenylbutazone Oxidation via Cu,Zn-SOD Peroxidase Activity: An EPR Study.

We investigated the effect of Cu,Zn-superoxide dismutase (Cu,Zn-SOD)-peroxidase activity on the oxidation of the nonsteroidal anti-inflammatory drug phenylbutazone (PBZ). We utilized electron paramagnetic resonance (EPR) spectroscopy to detect free radical intermediates of PBZ, UV-vis spectrophotometry to monitor PBZ oxidation, oxygen analysis to determine the involvement of C-centered radicals, and LC/MS to determine the resulting metabolites. Using EPR spectroscopy and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), we found that the spin adduct of CO3(•-) (DMPO/(•)OH) was attenuated with increasing PBZ concentrations. The resulting PBZ radical, which was assigned as a carbon-centered radical based on computer simulation of hyperfine splitting constants, was trapped by both DMPO and MNP spin traps. Similar to Cu,Zn-SOD-peroxidase activity, an identical PBZ carbon-centered radical was also detected with the presence of both myeloperoxidase (MPO/H2O2) and horseradish peroxidase (HRP/H2O2). Oxygen analysis revealed depletion in oxygen levels when PBZ was oxidized by SOD peroxidase-activity, further supporting carbon radical formation. In addition, UV-vis spectra showed that the λmax for PBZ (λ = 260 nm) declined in intensity and shifted to a new peak that was similar to the spectrum for 4-hydroxy-PBZ when oxidized by Cu,Zn-SOD-peroxidase activity. LC/MS evidence supported the formation of 4-hydroxy-PBZ when compared to that of a standard, and 4-hydroperoxy-PBZ was also detected in significant yield. These findings together indicate that the carbonate radical, a product of SOD peroxidase activity, appears to play a role in PBZ metabolism. Interestingly, these results are similar to findings from heme peroxidase enzymes, and the context of this metabolic pathway is discussed in terms of a mechanism for PBZ-induced toxicity.

Scavenging of free-radical metabolites of aniline xenobiotics and drugs by amino acid derivatives: toxicological implications of radical-transfer reactions.

We investigated a novel scavenging mechanism of arylamine free radicals by poly- and monoaminocarboxylates. Free radicals of arylamine xenobiotics and drugs did not react with oxygen in peroxidase-catalyzed reactions; however, they showed marked oxygen uptake in the presence of an aminocarboxylate. These free-radical intermediates were identified using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and electron paramagnetic resonance (EPR) spectrometry. Diethylenetriaminepentaacetic acid (DTPA), a polyaminocarboxylate, caused a concentration-dependent attenuation of N-centered radicals produced by the peroxidative metabolism of arylamines with the subsequent formation of secondary aliphatic carbon-centered radicals stemming from the cosubstrate molecule. Analogously, N,N-dimethylglycine (DMG) and N-methyliminodiacetate (MIDA), but not iminodiacetic acid (IDA), demonstrated a similar scavenging effect of arylamine-derived free radicals in a horseradish peroxidase/H2O2 system. Using human promyelocytic leukemia (HL-60) cell lysate as a model of human neutrophils, DTPA, MIDA, and DMG readily reduced anilinium cation radicals derived from the arylamines and gave rise to the corresponding carbon radicals. The rate of peroxidase-triggered polymerization of aniline was studied as a measure of nitrogen-radical scavenging. Although, IDA had no effect on the rate of aniline polymerization, this was almost nullified in the presence of DTPA and MIDA at half of the molar concentration of the aniline substrate, whereas a 20 molar excess of DMPO caused only a partial inhibition. Furthermore, the yield of formaldehyde, a specific reaction endproduct of the oxidation of aminocarboxylates by aniline free-radical metabolites, was quantitatively determined. Azobenzene, a specific reaction product of peroxidase-catalyzed free-radical dimerization of aniline, was fully abrogated in the presence of DTPA, as confirmed by GC/MS. Under aerobic conditions, a radical-transfer reaction is proposed between aminocarboxylates and arylamine free radicals via the carboxylic group-linked tertiary nitrogen of the deprotonated amino acid derivatives. These findings may have significant implications for the biological fate of arylamine xenobiotic and drug free-radical metabolites.

The effect of bicarbonate on menadione-induced redox cycling and cytotoxicity: potential involvement of the carbonate radical.

We have investigated the effect of NaHCO3 on menadione redox cycling and cytotoxicity. A cell-free system utilized menadione and ascorbic acid to catalyze a redox cycle, and we utilized murine hepatoma (Hepa 1c1c7) cells for in vitro experiments. Experiments were performed using low (2 mmol/L) and physiological (25 mmol/L) levels of NaHCO3 in buffer equilibrated to physiological pH. Using oximetry, ascorbic acid oxidation, and ascorbyl radical detection, we found that menadione redox cycling was enhanced by NaHCO3. Furthermore, Hepa 1c1c7 cells treated with menadione demonstrated cytotoxicity that was significantly increased with physiological concentrations of NaHCO3 in the media, compared with low levels of NaHCO3. Interestingly, the inhibition of superoxide dismutase (SOD) with 2 different metal chelators was associated with a protective effect against menadione cytotoxicity. Using isolated protein, we found a significant increase in protein carbonyls with menadione-ascorbate-SOD with physiological NaHCO3 levels; low NaHCO3 or SOD-free reactions produced lower levels of protein carbonyls. In conclusion, these findings suggest that the hydrogen peroxide generated by menadione redox cycling together with NaHCO3-CO2 are potential substrates for SOD peroxidase activity that can lead to carbonate-radical-enhanced cytotoxicity. These findings demonstrate the importance of NaHCO3 in menadione redox cycling and cytotoxicity.

The interaction of diamines and polyamines with the peroxidase-catalyzed metabolism of aromatic amines: a potential mechanism for the modulation of aniline toxicity.

Synthetic and biological amines such as ethylenediamine (EDA), spermine, and spermidine have not been previously investigated in free-radical biochemical systems involving aniline-based drugs or xenobiotics. We aimed to study the influence of polyamines in the modulation of aromatic amine radical metabolites in peroxidase-mediated free radical reactions. The aniline compounds tested caused a relatively low oxidation rate of glutathione in the presence of horseradish peroxidase (HRP), and H2O2; however, they demonstrated marked oxygen consumption when a polyamine molecule was present. Next, we characterized the free-radical products generated by these reactions using spin-trapping and electron paramagnetic resonance (EPR) spectrometry. Primary and secondary but not tertiary polyamines dose-dependently enhanced the N-centered radicals of different aniline compounds catalyzed by either HRP or myeloperoxidase, which we believe occurred via charge transfer intermediates and subsequent stabilization of aniline-derived radical species as suggested by isotopically labeled aniline. Aniline/peroxidase reaction product(s) were monitored at 435 nm by kinetic spectrophotometry in the presence and absence of a polyamine additive. Using gas chromatography-mass spectrometry, the dimerziation product of aniline, azobenzene, was significantly amplified when EDA was present. In conclusion, di- and poly-amines are capable of enhancing the formation of aromatic-amine-derived free radicals, a fact that is expected to have toxicological consequences.