Neurotoxic and cardiotoxic effects of pyrogallol on catfish (Clarias gariepinus).

Pyrogallol, a botanical hydrolysable tannin, has diverse medical and industrial applications. Its impact on aquatic ecosystems and fish health has been previously studied, revealing histopathological, immunological, biochemical, and haematological alterations in African catfish (Clarias gariepinus). In this study, the neurotoxic potential of pyrogallol was assessed through a 15-day exposure of catfish to concentrations of 1, 5, or 10 mg/L. Enzyme activities such as acetylcholinesterase (AchE), monoamine oxidase (MAO), aldehyde oxidase (AO), and nitric oxide (NO) were measured in serum and brain, along with histopathological examinations in the brain and heart. Pyrogallol exposure led to decreased AchE activity in the brain and serum, increased serum MAO activity, elevated AO in both brain and serum, and suppressed NO levels. Morphological abnormalities and dose-dependent pathological alterations were observed in the brain and heart, including neuropile deformities, shrunken Purkinje cells, cardiomyocyte degeneration, and increased collagen fibers. This suggests that pyrogallol induces adverse effects in fish.

Reproductive and endocrine-disrupting toxicity of pyrogallol in catfish (Clariasgariepinus).

Endocrine disruptors are synthetic or natural chemicals that can agonize/antagonize hormone receptors or can interfere with the production and secretion of hormones, leading to altered tissue histology and physiology. Pyrogallol is a contaminant widely distributed in aquatic environments that presents health risks to both humans and animals. However, the potential for endocrine disruption by pyrogallol, particularly in fish, are lacking. The purpose of this study was to shed light on how pyrogallol may affect hormone signalling, histopathology, and reproductive outcomes in African catfish Clarias gariepinus. To investigate this, African catfish were exposed to one sublethal concentration of pyrogallol at either 0, 1, 5 or 10 mg/L for 15 days. We then assessed the effects of pyrogallol on the thyroid gland as well as the reproductive system by measuring sex hormone, seminal quality, gonadal histopathology, and histochemistry. Thyroid stimulating hormone and thyroxine showed notable decreases in catfish, and triiodothyronine was decreased with 10 mg/L pyrogallol. Unlike luteinizing hormone, follicle-stimulating hormone was significantly reduced in fish following exposure to pyrogallol relative to controls. Testosterone was also decreased in fish following pyrogallol exposure, whereas 17ß-estradiol increased in catfish exposed to pyrogallol. Additionally, in response to pyrogallol toxicity, sperm quality indices, including count, spermatocrit, motility, and sperm viability were adversely affected in a concentration-dependent manner. Pyrogallol exposure also induced several changes in the gonad following exposure to 1, 5, or 10 mg/L. Deformed tubular structures, vacuolation, thickening of the basement membrane, hypertrophy of the seminiferous tubules, intense melanomacrophage localization, spermatozoa loss, and necrosis were all observed in the testes. In the ovary, atretic follicles, deteriorated mature oocytes, degenerated yolk globules, and an increase in perinucleolar oocytes were observed in catfish exposed to pyrogallol. These findings suggest that pyrogallol may act as endocrine disrupting substance in aquatic environments. Further research on the mechanisms by which pyrogallol impairs endocrine systems, particularly in fish, is recommended.

Immunotoxicological, histopathological, and ultrastructural effects of waterborne pyrogallol exposure on African catfish (Clariasgariepinus).

Pyrogallol is a naturally occurring polyphenol derived from natural plants, such as Acer rubrum and Eucalyptus sp. The current study was designed to evaluated pyrogallol-mediated toxicity at sublethal levels (1, 5, and 10 mg/L), derived from 96 h-LC50 values previously determined for African catfish (Clarias gariepinus). Immunotoxicological indices, histological, histochemical, and ultrastructural alterations in C. gariepinus were evaluated following a 15-day pyrogallol exposure. Pyrogallol decreased immune parameters [lysozyme activity (LYZ), immunoglobulin M (IgM), and phagocytic activity] and increased pro-inflammatory cytokines, interleukin-1 beta (IL-1ß), interleukin-6 (IL-6) in the serum of C. gariepinus. In addition, histopathology analysis demonstrated that exposure to pyrogallol induced injury in the liver and spleen of fish. Cellular changes in the liver include hepatocyte hydropic degeneration, melanomacrophage, vacuolated hepatocytes, congested blood, severe structural deformation, and hemorrhage. In the spleen, ellipsoid structures, melanomacrophage centers, and infiltration of inflammatory cells were evident. Together, a high frequency of histopathological lesions was scored in both the liver and spleen of C. gariepinus, which showed a dose-dependent relationship between pyrogallol exposure and histopathological indices. Our data suggest that dysfunction in the immune system may be mediated by pyrogallol-induced changes in cytokines.

Oxidative stress, antioxidant defense responses, and histopathology: Biomarkers for monitoring exposure to pyrogallol in Clarias gariepinus.

Pyrogallol promotes free radicals leading to oxidative stress and toxicity. There are however a lack of studies on oxidative stress and the antioxidant system of fish following exposure to pyrogallol. This study measured oxidative stress markers, antioxidant responses, and histological changes in catfish exposed to pyrogallol. Fish were divided into one of four experimental groups: control only, or 1, 5 or 10 mg/L pyrogallol. After 15 days, glutathione-S-transferase in the serum was decreased in fish exposed to either 5 or 10 mg/L pyrogallol relative to controls while superoxide dismutase and total antioxidant capacity were decreased significantly in fish exposed to 1, 5, or 10 mg/L pyrogallol. Conversely, catalase was increased in serum of fish exposed to 1, 5, or 10 mg/L pyrogallol compared to controls. The liver of fish treated with 1, 5, or 10 mg/L pyrogallol had significantly higher levels of oxidative stress markers (malondialdehyde, lipid peroxidation, hydroperoxide content, oxidised protein content, and DNA fragmentation %) that varied with concentration. Catfish exposed to either 1, 5, or 10 mg/L pyrogallol presented with notable histological alterations in the intestine, kidney, and muscles with prominent fibrosis, as intense deposition of collagen fibre was observed by Masson's trichrome staining. Overall, endpoints related to oxidative stress and antioxidant defence enzymes in fish may be early biomarkers of pyrogallol exposure and contamination in aquatic ecosystems. Additional studies should characterize oxidative stress indicators for their utility as biomarkers of effect.

Exposure to pyrogallol impacts the hemato-biochemical endpoints in catfish (Clarias gariepinus).

Pyrogallol is widely used in several industrial applications and can subsequently contaminate aquatic ecosystems. Here, we report for the first time the presence of pyrogallol in wastewater in Egypt. Currently, there is a complete lack of toxicity and carcinogenicity data for pyrogallol exposure in fish. To address this gap, both acute and sub-acute toxicity experiments were conducted to determine the toxicity of pyrogallol in catfish (Clarias gariepinus). Behavioral and morphological endpoints were evaluated, in addition to blood hematological endpoints, biochemical indices, electrolyte balance, and the erythron profile (poikilocytosis and nuclear abnormalities). In the acute toxicity assay, it was determined that the 96 h median-lethal concentration (96 h-LC50) of pyrogallol for catfish was 40 mg/L. In sub-acute toxicity experiment, fish divided into four groups; Group 1 was the control group. Group 2 was exposed to 1 mg/L of pyrogallol, Group 3 was exposed to 5 mg/L of pyrogallol, and Group 4 was exposed to 10 mg/L of pyrogallol. Fish showed morphological changes such as erosion of the dorsal and caudal fins, skin ulcers, and discoloration following exposure to pyrogallol for 96 h. Exposure to 1, 5, or 10 mg/L pyrogallol caused a significant decrease in hematological indices, including red blood cells (RBCs), hemoglobin, hematocrit, white blood cells (WBC), thrombocytes, and large and small lymphocytes in a dose-dependent manner. Several biochemical parameters (creatinine, uric acid, liver enzymes, lactate dehydrogenase, and glucose) were altered in a concentration dependent manner with short term exposures to pyrogallol. Pyrogallol exposure also caused a significant concentration-dependent rise in the percentage of poikilocytosis and nuclear abnormalities of RBCs in catfish. In conclusion, our data suggest that pyrogallol should be considered further in environmental risk assessments of aquatic species.

Elemicin exposure induced aberrant lipid metabolism via modulation of gut microbiota in mice.

Elemicin (Ele) is a constituent of natural alkenylbenzene present in many foods and herbs. Ele exposure could induce hepatomegaly and hepatosteatosis. However, the role of gut microbiota in Ele-induced hepatotoxicity remains unclear. Here, the mice were treated with 200 mg/kg/day of Ele for 4 weeks with or without depletion of gut microbiota by antibiotics cocktail treatment. The mice treated with Ele showed enlargement of liver and slight hepatosteatosis, accompanied by higher levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG). Ele could also shift the structure of fecal microbiota and increase the richness. Functional prediction of the microbiota revealed the enrichment of non-alcoholic fatty liver disease pathway upon Ele exposure. Compared with control group, Patescibacteria and Epsilonbacteraeota were significantly enriched at the phylum level upon Ele treatment. A total of 20 genera were significant with respect specifically to Ele exposure, including decreased Alistipes and elevated Ruminiclostridium_9 and Gordonibacter. Among them, 13 retained significant associations with ALT and TG by Spearman correlation test, 4 were correlated with AST. Further MaAsLin analysis revealed that ALT was associated with 4 differentially abundant genera, such as Alistipes and Ruminiclostridium_9 and Gordonibacter. In addition, only Alistipes was significantly correlated with serum TG. Intriguingly, depletion of the microbiota significantly attenuated hepatosteatosis, restore increased ALT, AST and TG and inhibit the expression of genes involved in de novo lipogenesis and adipocyte differentiation, such as Fasn, ADIPOQ and leptin. Collectively, depletion of gut microbiota protected against Ele induced aberrant lipid metabolism in mice.

The impact of differential lignin S/G ratios on mutagenicity and chicken embryonic toxicity.

Lignin and lignin-based materials have received considerable attention in various fields due to their promise as sustainable feedstocks. Guaiacol (G) and syringol (S) are two primary monolignols that occur in different ratios for different plant species. As methoxyphenols, G and S have been targeted as atmospheric pollutants and their acute toxicity examined. However, there is a rare understanding of the toxicological properties on other endpoints and mixture effects of these monolignols. To fill this knowledge gap, our study investigated the impact of different S/G ratios (0.5, 1, and 2) and three lignin depolymerization samples from poplar, pine, and miscanthus species on mutagenicity and developmental toxicity. A multitiered method consisted of in silico simulation, in vitro Ames test, and in vivo chicken embryonic assay was employed. In the Ames test, syringol showed a sign of mutagenicity, whereas guaiacol did not, which agreed with the T.E.S.T. simulation. For three S and G mixture and lignin monomers, mutagenic activity was related to the proportion of syringol. In addition, both S and G showed developmental toxicity in the chicken embryonic assay and T.E.S.T. simulation, and guaiacol had a severe effect on lipid peroxidation. A similar trend and comparable developmental toxicity levels were detected for S and G mixtures and the three lignin depolymerized monomers. This study provides data and insights on the differential toxicity of varying S/G ratios for some important building blocks for bio-based materials.

Chemical Composition and Preliminary Toxicity Evaluation of the Essential Oil from Peperomia circinnata Link var. circinnata. (Piperaceae) in Artemia salina Leach.

Peperomia Ruiz and Pav, the second largest genus of the Piperaceae, has over the years shown potential biological activities. In this sense, the present work aimed to carry out a seasonal and circadian study on the chemical composition of Peperomia circinata essential oils and aromas, as well as to evaluate the preliminary toxicity in Artemia salina Leach and carry out an in silico study on the interaction mechanism. The chemical composition was characterized by gas chromatography (GC/MS and GC-FID). In the seasonal study the essential oil yields had a variation of 1.2-7.9%, and in the circadian study the variation was 1.5-5.6%. The major compounds in the seasonal study were ß-phellandrene and elemicin, in the circadian they were ß-phellandrene and myrcene, and the aroma was characterized by the presence of ß-phellandrene. The multivariate analysis showed that the period and time of collection influenced the essential oil and aroma chemical composition. The highest toxicity value was observed for the essential oil obtained from the dry material, collected in July with a value of 14.45 ± 0.25 µg·mL-1, the in silico study showed that the major compounds may be related to potential biological activity demonstrated by the present study.

Quantitatively Tracking Bio-Nano Interactions of Metal-Phenolic Nanocapsules by Mass Cytometry.

Polymer nanocapsules, with a hollow structure, are increasingly finding widespread use as drug delivery carriers; however, quantitatively evaluating the bio-nano interactions of nanocapsules remains challenging. Herein, poly(ethylene glycol) (PEG)-based metal-phenolic network (MPN) nanocapsules of three sizes (50, 100, and 150 nm) are engineered via supramolecular template-assisted assembly and the effect of the nanocapsule size on bio-nano interactions is investigated using in vitro cell experiments, ex vivo whole blood assays, and in vivo rat models. To track the nanocapsules by mass cytometry, a preformed gold nanoparticle (14 nm) is encapsulated into each PEG-MPN nanocapsule. The results reveal that decreasing the size of the PEG-MPN nanocapsules from 150 to 50 nm leads to reduced association (up to 70%) with phagocytic blood cells in human blood and prolongs in vivo systemic exposure in rat models. The findings provide insights into MPN-based nanocapsules and represent a platform for studying bio-nano interactions.

Enhanced resistance of co-existing toxigenic and non-toxigenic Microcystis aeruginosa to pyrogallol compared with monostrains.

Cyanobacteria species are sensitive to many plant allelochemicals, such as pyrogallol. However, little attention has been paid to the relative effects of these xenobiotics on co-occurring toxigenic and non-toxigenic cyanobacterial strains, despite their co-existence in blooms. Hence, the responses of one toxigenic (TS2) and two non-toxigenic (NS1, NS2) Microcystis aeruginosa strains to pyrogallol were tested under three conditions: mono-culture and co-cultured either directly or separately by dialysis membrane. The study showed that the inhibitory effects of pyrogallol on the growth and photosynthetic yield (Fv/Fm) of either toxigenic or non-toxigenic M. aeruginosa strains were lower in direct and dialysis co-culture conditions than those in mono-culture conditions. This result indicated that chemical-mediated reciprocal effects occur between the co-existing toxigenic and non-toxigenic strains. The toxigenic M. aeruginosa strain was more sensitive to pyrogallol than the non-toxigenic strains in both mono- and co-culture systems, though whether this outcome is due to the former's toxigenic status is unclear. Intracellular microcystin-LR (MC-LR) concentrations of the toxigenic strain decreased after pyrogallol addition in both mono- and co-culture systems, whereas extracellular MC-LR concentrations increased. This finding may reflect the cell damage of M. aeruginosa because of the pyrogallol. At the same initial number of cells, the extracellular MC-LR concentration released from the same amount of TS2 cells in mono-culture was slightly higher than that in dialysis co-culture conditions. Overall, this study shows that plant allelochemicals may have the potential to reduce bloom toxicity by reducing the proportion of toxigenic cyanobacterial strains, and the effects of co-existing strains must be considered when assessing the effects of plant allelochemicals on target strains.

Role of Metabolic Activation in Elemicin-Induced Cellular Toxicity.

Elemicin, an alkenylbenzene constituent of natural oils of several plant species, is widely distributed in food, dietary supplements, and medicinal plants. 1'-Hydroxylation is known to cause metabolic activation of alkenylbenzenes leading to their potential toxicity. The aim of this study was to explore the relationship between elemicin metabolism and its toxicity through comparing the metabolic maps between elemicin and 1'-hydroxyelemicin. Elemicin was transformed into a reactive metabolite of 1'-hydroxyelemicin, which was subsequently conjugated with cysteine (Cys) and N-acetylcysteine (NAC). Administration of NAC could significantly ameliorate the elemicin- and 1'-hydroxyelemicin-induced cytotoxicity of HepG2 cells, while depletion of Cys with diethyl maleate (DEM) increased cytotoxicity. Recombinant human CYP screening and CYP inhibition experiments revealed that multiple CYPs, notably CYP1A1, CYP1A2, and CYP3A4, were responsible for the metabolic activation of elemicin. This study revealed that metabolic activation plays a critical role in elemicin cytotoxicity.

Metabolic Activation of Myristicin and Its Role in Cellular Toxicity.

Myristicin is widely distributed in spices and medicinal plants. The aim of this study was to explore the role of metabolic activation of myristicin in its potential toxicity through a metabolomic approach. The myristicin- N-acetylcysteine adduct was identified by comparing the metabolic maps of myristicin and 1'-hydroxymyristicin. The supplement of N-acetylcysteine could protect against the cytotoxicity of myristicin and 1'-hydroxymyristicin in primary mouse hepatocytes. When the depletion of intracellular N-acetylcysteine was pretreated with diethyl maleate in hepatocytes, the cytotoxicity induced by myristicin and 1'-hydroxymyristicin was deteriorated. It suggested that the N-acetylcysteine adduct resulting from myristicin bioactivation was closely associated with myristicin toxicity. Screening of human recombinant cytochrome P450s (CYPs) and treatment with CYP inhibitors revealed that CYP1A1 was mainly involved in the formation of 1'-hydroxymyristicin. Collectively, this study provided a global view of myristicin metabolism and identified the N-acetylcysteine adduct resulting from myristicin bioactivation, which could be used for understanding the mechanism of myristicin toxicity.

Microbial metabolites of proanthocyanidins reduce chemical carcinogen-induced DNA damage in human lung epithelial and fetal hepatic cells in vitro.

Seven selected microbial metabolites of proanthocyanidins (MMP), 3-phenylpropionic, 4-hydroxyphenyl acetic, 3-(4-hydroxyphenyl) propionic, p-coumaric, benzoic acid, pyrogallol (PG), and pyrocatechol (PC) were evaluated for their ability to reduce chemical carcinogen-induced toxicity in human lung epithelial cells (BEAS-2B) and human fetal hepatic cells (WRL-68). Cells pre-treated with MMP were exposed to a known chemical carcinogen, 4-[(acetoxymethyl) nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc) to assess MMP-mediated cytoprotection and reduction of DNA damage. PG in BEAS-2B and PC in WRL-68 cells mitigated the NNKOAc-induced cytotoxicity. Pre-incubation of PG depicted significant protection against NNKOAc-induced DNA damage in BEAS-2B cells. PC in WRL-68 cells showed similar activity. To understand the mechanisms of PG- and PC-mediated DNA damage reduction, the effect on DNA damage response (DDR) proteins, cellular reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and caspase activity were studied. PG and PC alter the DDR and may promote ATR-Chk1 and ATM-Chk2 pathways, respectively. Cellular oxidative stress induced by NNKOAc was mitigated by PG and PC through enhanced GPx expression and TAC. PG and PC suppressed the activation of the extrinsic apoptotic pathway (caspase 3 and 8) provoked by NNKOAc. MMP are beneficial in chemoprevention by reducing cellular DNA damage.

Insecticidal Activity of the Leaf Essential Oil of Peperomia borbonensis Miq. (Piperaceae) and Its Major Components against the Melon Fly Bactrocera cucurbitae (Diptera: Tephritidae).

The essential oil from the leaves of Peperomia borbonensis from Réunion Island was obtained by hydrodistillation and characterized using GC-FID, GC/MS and NMR. The main components were myristicin (39.5%) and elemicin (26.6%). The essential oil (EO) of Peperomia borbonensis and its major compounds (myristicin and elemicin), pure or in a mixture, were evaluated for their insecticidal activity against Bactrocera cucurbitae (Diptera: Tephritidae) using a filter paper impregnated bioassay. The concentrations necessary to kill 50% (LC50 ) and 90% (LC90 ) of the flies in three hours were determined. The LC50 value was 0.23 ± 0.009 mg/cm2 and the LC90 value was 0.34 ± 0.015 mg/cm2 for the EO. The median lethal time (LT50 ) was determined to compare the toxicity of EO and the major constituents. The EO was the most potent insecticide (LT50  = 98 ± 2 min), followed by the mixture of myristicin and elemicin (1.4:1) (LT50  = 127 ± 2 min) indicating that the efficiency of the EO is potentiated by minor compounds and emphasizing one of the major assets of EOs against pure molecules.

Effects of pyrogallic acid on Microcystis aeruginosa: oxidative stress related toxicity.

Pyrogallic acid (PA) is used in various industrial and consumer products. The molecular mechanisms underlying PA's toxicity was not fully understood. In this study, toxicity of PA on Microcystis aeruginosa with reactive oxygen species (ROS) generation as an end point was investigated. The results showed an increase in the percentage of cells with loss of membrane integrity and enhanced intracellular ROS production. Exposure to 50mgL(-1) PA for 48h caused the highest percentage of loss of membrane integrity (56.7%), and a 2.54-fold higher intracellular ROS level compared to control. Further investigation revealed that PA caused a dose-dependent increase in DNA strand breaks (DSB) of M. aeruginosa at exposure concentration from 2 to 50mgL(-1). The incubation of cells with ROS scavengers ascorbic acid, N-acetyl-l-cysteine (NAC) and tocopherol markedly alleviated the level of PA-induced DSB. Analysis of PA autoxidized products in culture solution showed that PA was quickly converted to purpurogallin (PG), and PG was further autoxidized to other polyphenolic compounds. PA and PG might participate a futile redox cycle, which mediated ROS production in M. aeruginosa. These results suggested DNA strands and cell membrane were two targets of ROS induced by PA, and oxidative damage was an important mechanism for the toxicity of PA against M. aeruginosa.

Contact sensitizing potential of pyrogallol and 5-amino-o-cresol in female BALB/c mice.

Hair dye components such as pyrogallol and cresol have been shown previously to promote allergic reactions such as rashes, dermal inflammation, irritation and dermatitis. The objective of this study was to determine the contact sensitization potential of pyrogallol (PYR) and 5-amino-o-cresol (AOC) when applied dermally to female BALB/c mice. Measurement of the contact hypersensitivity response was initially accomplished using the local lymph node assay. For PYR, significant increases in the proliferation of lymph node cells were observed at concentrations of 0.5% (w/v) and higher. For AOC, borderline increases, albeit significant, in auricular lymph node cell proliferation were observed at 5% and 10%. Results from the irritancy assay suggested that PYR, but not AOC, was an irritant. To further delineate whether PYR was primarily an irritant or a contact sensitizer, the mouse ear swelling test (MEST) was conducted. A significant increase in mouse ear thickness was observed at 72h following challenge with 0.5% PYR in mice that had been sensitized with 5% PYR. In contrast, no effects were observed in the MEST in mice sensitized and challenged with the highest achievable concentration of AOC (10%). Additional studies examining lymph node subpopulations and CD86 (B7.2) expression by B cells further support the indication that PYR was a sensitizer in BALB/c mice. The results demonstrate that PYR is both a sensitizer and an irritant in female BALB/c mice. However, the contact sensitization potential of AOC is minimal in this strain of mouse.

Methanol extract from the stem of Cotinus coggygria Scop., and its major bioactive phytochemical constituent myricetin modulate pyrogallol-induced DNA damage and liver injury.

The present study was undertaken to investigate the hepatoprotective effect of the methanol extract of Cotinus coggygria Scop. in rats exposed to the hepatotoxic compound pyrogallol. Assessed with the alkaline version of the comet assay, 1000 and 2000mg/kg body weight (bw) of the extract showed a low level of genotoxicity, while 500mg/kg bw of the extract showed no genotoxic potential. Quantitative HPLC analysis of phenolic acids and flavonoids in the methanol extract of C. coggygria showed that myricetin was a major component. To test the hepatoprotective effect, a non-genotoxic dose of the C. coggygria extract and an equivalent amount of synthetic myricetin, as present in the extract, were applied either 2 or 12h prior to administration of 100mg/kg bw of pyrogallol. The extract and myricetin promoted restoration of hepatic function by significantly reducing pyrogallol-induced elevation in the serum enzymes AST, ALT, ALP and in total bilirubin. As measured by the decrease in total score and tail moment, the DNA damage in liver was also reduced by the extract and by myricetin. Our results suggest that pro-surviving Akt activity and STAT3 protein expression play important roles in decreasing DNA damage and in mediating hepatic protection by the extract. These results suggest that myricetin, as a major component in the extract, is responsible for the antigenotoxic and hepatoprotective properties of the methanol extract of C. coggygria against pyrogallol-induced toxicity.

Toxicology and carcinogenesis studies of pyrogallol (CAS No. 87-66-1) in F344/N rats and B6C3F1/N mice (dermal studies).

UNLABELLED: The current main commercial use of pyrogallol is the production of pharmaceuticals and pesticides. In analytical chemistry, pyrogallol is used as a complexing agent, reducing agent, and, in alkaline solution, as an indicator of gaseous oxygen. Pyrogallol was nominated for testing by private individuals based on its frequent occurrence in natural and manufactured products, including hair dyes, and the apparent lack of carcinogenicity data. Male and female F344/N rats and B6C3F1/N mice were administered pyrogallol (99% pure) dermally for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats received dermal applications of pyrogallol in 95% ethanol at doses of 0, 9.5, 18.75, 37.5, 75, or 150 mg pyrogallol/kg body weight, 5 days per week for 14 weeks. Additional groups of 10 male and 10 female special study rats were administered the same doses, 5 days per week for 23 days. All rats survived until the end of the study except for one vehicle control female. Mean body weights of dosed groups of males and females were generally similar to those of the vehicle controls. Chemical-related clinical findings included brown staining and irritation of the skin at the site of application. There were no changes in the hematology, serum clinical chemistry, thyroid hormone values, or organ weights attributable to the dermal administration of pyrogallol. The incidences of squamous hyperplasia, hyperkeratosis, and chronic active inflammation of the skin at the site of application were significantly increased in all dosed groups of males and females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice received dermal applications of pyrogallol in 95% ethanol at doses of 0, 38, 75, 150, 300, or 600 mg pyrogallol/kg body weight, 5 days per week for 14 weeks. All mice survived until the end of the study. Mean body weights of dosed groups of males and females were similar to those of the vehicle controls. Chemical-related clinical findings included brown staining and irritation at the site of application. There were no changes in the hematology values or organ weights attributable to the dermal administration of pyrogallol. The incidences of squamous hyperplasia, hyperkeratosis, and chronic active inflammation of the skin at the site of application were significantly increased in all dosed groups of males and females. The incidence of hematopoietic cell proliferation of the spleen in 600 mg/kg males was significantly greater than that in the vehicle control group. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats received dermal applications of pyrogallol in 95% ethanol at doses of 0, 5, 20, or 75 mg pyrogallol/kg body weight, 5 days per week for up to 104 weeks. Survival of dosed groups of male and female rats was similar to that of the vehicle control groups. Mean body weights of dosed male and female rats were similar to those of the vehicle control groups throughout the study. Irritation of the skin at the site of application was the only chemical-related clinical finding and occurred in the 20 and 75 mg/kg groups. In the skin at the site of application, there were significant increases in the incidences of hyperplasia in all dosed groups of males and females, hyperkeratosis in 20 and 75 mg/kg males and all dosed groups of females, inflammation in 75 mg/kg males and 20 and 75 mg/kg females, and sebaceous gland hyperplasia in 20 and 75 mg/kg males and females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice received dermal applications of pyrogallol in 95% ethanol at doses of 0, 5, 20, or 75 mg pyrogallol/kg body weight, 5 days per week for up to 105 weeks. Survival of dosed groups of male mice was similar to that of the vehicle control group. Survival was significantly decreased in 75 mg/kg females; most early deaths in this group were due to ulcers at or adjacent to the site of application. The mean body weights of 75 mg/kg female mice were generally over 10% less than those of the vehicle controls during year 2 of the study. Irritation and/or ulceration of the skin at the site of application were the only chemical-related clinical findings and occurred predominantly in the 20 and 75 mg/kg groups. In the skin at the site of application, the incidence of squamous cell carcinoma in 75 mg/kg females was significantly greater than that in the vehicle control group. Two 75 mg/kg males had squamous cell papillomas; squamous cell papillomas have not been observed in historical control male mice in four ethanol dermal studies. Increased incidences of nonneoplastic lesions at the site of application included hyperplasia and hyperkeratosis in all dosed groups; inflammation, fibrosis, and pigmentation in the 20 and 75 mg/kg groups; and sebaceous gland hyperplasia and ulcer in the 75 mg/kg groups. Similar lesions in the skin of the neck and back immediately adjacent to the site of application were observed; the incidences of hyperplasia, hyperkeratosis, ulcer, inflammation, and fibrosis at these sites were significantly increased in 75 mg/kg male and female mice, and the incidence of sebaceous gland hyperplasia was significantly increased in 75 mg/kg female mice. Dermal application of pyrogallol also resulted in significant increases in the incidences of bone marrow hyperplasia in males and females and lymphoid hyperplasia of the axillary, inguinal, and mandibular lymph nodes; adrenal cortical hematopoietic cell proliferation; and mammary gland hyperplasia in females. GENETIC TOXICOLOGY: Pyrogallol was tested in two independent bacterial mutation studies; both studies gave positive results in one or more strains of S. typhimurium or E. coli. In the first study, positive results were seen in S. typhimurium strain TA100 with and without S9 exogenous metabolic activation, and negative results were obtained in strain TA98. In the second study, which was conducted with the same lot of pyrogallol that was used in the 3-month and 2-year studies, positive results were obtained in S. typhimurium strains TA98, TA100, and in E. coli strain WP2 uvrA/pKM101 in the absence of S9. With S9, this sample of pyrogallol was mutagenic in the E. coli strain but gave equivocal responses in S. typhimurium strains TA98 and TA100. In vivo, a micronucleus test that measured frequency of micronucleated polychromatic erythrocytes in bone marrow of male B6C3F1/N mice following three intraperitoneal injections of pyrogallol, gave negative results. In a second in vivo test, no increase in the frequency of micronucleated erythrocytes was observed in the peripheral blood of female B6C3F1/N mice treated with pyrogallol via dermal application for 3 months; in male mice, however, results were equivocal, based on a significant increase in micronucleated erythrocytes observed at a single dose level at the end of the 3-month study. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of pyrogallol in male or female F344/N rats administered 5, 20, or 75 mg/kg. There was equivocal evidence of carcinogenic activity of pyrogallol in male B6C3F1/N mice based on increased incidences of squamous cell papilloma of the skin at the site of application. There was some evidence of carcinogenic activity of pyrogallol in female B6C3F1/N mice based on increased incidences of squamous cell carcinoma of the skin at the site of application. Dermal administration of pyrogallol caused increased incidences of nonneoplastic lesions of the skin at the site of application in male and female rats and mice, skin adjacent to the site of application in male and female mice, and mammary gland in female mice.

Pyrogallol-associated dermal toxicity and carcinogenicity in F344/N rats and B6C3F1/N mice.

Pyrogallol (CAS No. 87-66-1), a benzenetriol used historically as a hair dye and currently in a number of industrial applications, was nominated to the National Toxicology Program (NTP) for testing based on the lack of toxicity and carcinogenicity data. Three-month and two-year toxicity studies to determine the toxicity and carcinogenicity of pyrogallol when applied to naïve skin (i.e. dermal administration) were conducted in both sexes of F344/N rats and B6C3F1/N mice. In the three-month studies, adult rodents were administered pyrogallol in 95% ethanol five days per week for 3 months at doses of up to 150 mg/kg body weight (rats) or 600 mg/kg (mice). Based on the subchronic studies, the doses for the two-year studies in rats and mice were 5, 20 and 75 mg/kg of pyrogallol. All mice and most rats survived until the end of the three-month study and body weights were comparable to controls. During the two-year study, survival of dosed rats and male mice was comparable to controls; however survival of 75 mg/kg female mice significantly decreased compared to controls. The incidences of microscopic non-neoplastic lesions at the site of application were significantly higher in all dosed groups of rats and mice and in both the 3-months and two-year studies. In the two-year study, hyperplasia, hyperkeratosis and inflammation tended to be more severe in mice than in rats, and in the mice they tended to be more severe in females than in males. The incidence of squamous cell carcinoma at the site of application (SOA) in 75 mg/kg female mice and SOA squamous cell papillomas in 75 mg/kg male mice were greater than controls. Pyrogallol was carcinogenic in female mice and may have caused tumors in male mice.

The effect of pyrogallic acid on growth, oxidative stress, and gene expression in Cylindrospermopsis raciborskii (Cyanobacteria).

In order to investigate the effect of the allelopathic compound pyrogallic acid on Cylindrospermopsis raciborskii F2, the impact on growth, oxidative stress and expression of the psbA, grpE, fabZ, recA, cmpA, ftsZ and cyrJ genes were studied. The results indicated significant decreases in Chl a and cell number following a 24-h incubation with 4 mg L(-1) pyrogallic acid. Additionally, malodialdehyde content, superoxide dismutase activity and catalase activity were enhanced following treatment with 2 and 4 mg L(-1) pyrogallic acid. Expressions of the genes psbA, grpE, fabZ, recA and cyrJ were significantly up-regulated following exposure to 4 mg L(-1) pyrogallic acid, while no changes were observed with concentrations of 1 or 2 mg L(-1). Expression of cmpA was significantly down-regulated following treatment with the lowest tested concentration of pyrogallic acid (1 mg L(-1)), while ftsZ was only significantly down-regulated with concentrations of 2 and 4 mg L(-1). These results suggest that photosynthesis inhibition and oxidative damage are important modes of action for the allelopathic effect of pyrogallic acid on C. raciborskii.