Characterization of the LOAEL-to-NOAEL uncertainty factor for mild adverse effects from acute inhalation exposures

Computational Insights into Reproductive Toxicity: Clustering, Mechanism Analysis, and Predictive Models

Reproductive toxicity poses significant risks to fertility and progeny health, making its identification in pharmaceutical compounds crucial. In this study, we conducted a comprehensive in silico investigation of reproductive toxic molecules, identifying three distinct categories represented by Dimethylhydantoin, Phenol, and Dicyclohexyl phthalate. Our analysis included physicochemical properties, target prediction, and KEGG and GO pathway analyses, revealing diverse and complex mechanisms of toxicity. Given the complexity of these mechanisms, traditional molecule-target research approaches proved insufficient. Support Vector Machines (SVMs) combined with molecular descriptors achieved an accuracy of 0.85 in the test dataset, while our custom deep learning model, integrating molecular SMILES and graphs, achieved an accuracy of 0.88 in the test dataset. These models effectively predicted reproductive toxicity, highlighting the potential of computational methods in pharmaceutical safety evaluation. Our study provides a robust framework for utilizing computational methods to enhance the safety evaluation of potential pharmaceutical compounds.

Phenolic profile, acute and subacute oral toxicity of the aqueous extract from Moroccan Mentha longifolia L. aerial part in Swiss Albino mice model

ETHNOPHARMACOLOGICAL RELEVANCE

Mentha longifolia (L.) (Lamiaceae) is a native plant in Morocco, traditionally used in different countries to treat several disorders notably gastrointestinal illnesses, respiratory disorders, infectious diseases, inflammatory diseases, and menstrual problems. Robust scientific evidence has confirmed multiple pharmacological properties of M. longifolia including antihemolytic, anti-inflammatory, antibacterial, hepatoprotective, anti-cancer, antidiabetic, gastroprotective effect, and antispasmodic activity.

AIM OF THE STUDY

The current study aimed to determine the phytochemical profile and assess the toxic effect of an aqueous extract of the arial parts of M. longifolia in male and female Swiss albino mice during acute and subacute oral toxicity.

MATERIALS AND METHODS

High-performance Liquid Chromatography Diode Array Detector (HPLC-DAD) was used to provide qualitative and quantitative analyses of phenolic compounds of M. longifolia aqueous extract. In acute toxicity experiments, four distinct groups of mice (n = 5/group/sex) were administered Mentha longifolia aqueous extract at single oral dosages of 0.5; 1; 2; 4, and 8 g/kg BW given by gavage and intraperitoneal for up to 14 days. Regarding the subacute toxicity investigation, Swiss albino mice were given M. longifolia aqueous extract orally at dosages of 100; 500; and 1000 mg/kg BW daily for 28 days. Body weight is measured every 7 days and suggested biochemical and hematological parameters were quantified, at the finish of 28 days of daily administration, sections of the liver, kidney, and spleen were histologically evaluated for showing damage to organs.

RESULTS

The data of High-performance Liquid chromatography analysis revealed that M. longifolia aqueous extract was rich in interesting phytochemical compounds, mainly quercetin, and rutin, followed by a hydroxybenzoic acid-like syringic acid. Regarding the acute test in mice, no mortality or symptoms of toxicity were detected following oral administration with a single dose of M. longifolia aqueous extract at any dosage limit up to 4 g/kg, which was the no-observed side effect threshold (NOAEL). The mortality rate as well as acute toxicity of the M. longifolia aqueous extract delivered intraperitoneally, are increased progressively with increasing dosage. The non-observed adverse effect level (NOAEL) for the intraperitoneal dosage was 1 g/kg BW, and the lowest observed adverse effect level (LOAEL) was 2 g/kg BW, the estimated acute toxicity (LD50) of intraperitoneally given M. longifolia aqueous extract in mice was 4.800 g/kg BW. Concerning subacute examinations in mice, the M. longifolia aqueous extract did not induce substantial modifications in biochemical or hematological indicators, preserving a slight increase in creatinine and urea levels. At the end of the experiment, a histopathological examination of the kidneys, liver, and spleen revealed normal architecture, suggesting no morphological damage.

CONCLUSION

The data we obtained indicate that acute or subacute administration of Mentha longifolia aqueous extract is relatively non-toxic in male and female Swiss albino mice.

The Application of Reference Dose Prediction Model to Human Health Water Quality Criteria and Risk Assessment

Oral reference dose (RfD) is a key parameter for deriving the human health ambient water quality criteria (AWQC) for non-carcinogenic substances. In this study, a non-experimental approach was used to calculate the RfD values, which explore the potential correlation between toxicity and physicochemical characteristics and the chemical structure of pesticides. The molecular descriptors of contaminants were calculated using T.E.S.T software from EPA, and a prediction model was developed using a stepwise multiple linear regression (MLR) approaches. Approximately 95% and 85% of the data points differ by less than 10-fold and 5-fold between predicted values and true values, respectively, which improves the efficiency of RfD calculation. The model prediction values have certain reference values in the absence of experimental data, which is beneficial to the advancement of contaminant health risk assessment. In addition, using the prediction model constructed in this manuscript, the RfD values of two pesticide substances in the list of priority pollutants are calculated to derive human health water quality criteria. Furthermore, an initial assessment of the health risk was performed by the quotient value method based on the human health water quality criteria calculated by the prediction model.

Safety evaluation of aqueous extract from Eugenia uniflora leaves: Acute and subacute toxicity and genotoxicity in vivo assays

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia uniflora Linn (Myrtaceae) is the native species of Brazil. The leaves of this species are used in folk medicine to treat different inflammatory and gastrointestinal disorders. However, research on the safety of using E. uniflora leaves has been poorly explored.

AIM OF THE STUDY

This approach aims to investigate the phytochemical composition as well as the acute, subacute toxicity, and in vivo genotoxic profile of the aqueous extract of E. uniflora leaves.

MATERIALS AND METHODS

The chemical composition of E. uniflora leaf extract was determined by Fingerprint by High-Performance Thin Layer and High-Performance Liquid Chromatography. The acute toxicity in vivo was evaluated for 14 days after the administration of E. uniflora leaves extract (2000 mg/kg). For the evaluation of subacute toxicity, mice were daily treated for 28 days with E. uniflora extract (250, 500, or 1000 mg/kg). Signs of behavioral toxicity and biochemical and hematological alterations, including the multiple organ toxicities were investigated. In addition, the micronucleus assay was used to evaluate the in vivo genotoxicity of the leaves extract in murine erythrocytes.

RESULTS

The phytochemical analysis showed the majority presence of phenolic compounds (gallic acid, ellagic acid, and myricitrin). Single or repeated doses of the aqueous extract of E. uniflora leaves did not reveal any signs of in vivo toxicity. Daily doses of the extract for 28 days induced a slight reduction in cholesterol and triglyceride levels. Furthermore, E. uniflora leaves extract (1000-2000 mg/kg) showed no genetic damage in the micronucleus assay, indicating the absence of genotoxicity of the herbal species.

CONCLUSION

The aqueous extract of E. uniflora leaves showed a predominance of phenolic compounds, with non-toxic and non-genotoxic action in vivo. This approach sheds light on the chemical composition of the leaves of E. uniflora and suggests a high margin of safety in the popular use of the leaves of this plant species.

Evaluation of acute toxicity, 28-day repeated dose toxicity, and genotoxicity of Moringa oleifera leaves infusion and powder

ETHNOPHARMACOLOGICAL RELEVANCE

Moringa oleifera Lam. leaves infusion and powder are widely used by population due the nutritional and medicinal potentials, however data regarding safety of use are still inconclusive, leading to prohibition of this plant in some countries.

AIM OF THE STUDY

The present work investigated the nutritional and phytochemical composition, acute and 28-day repeated dose toxicity, and genotoxicity of M. oleifera leaves infusion and powder.

MATERIALS AND METHODS

For nutritional characterization of leaf powder, it was determined: humidity; mineral residue (ash); total lipid, protein, carbohydrate, and crude fiber contents; and total caloric value. Phytochemical composition was determined by high performance liquid chromatography (HPLC). The acute toxicity assay used Swiss female albino mice and oral administration in a single dose at 2000 and 5000 mg/kg of infusion or powder. The 28-day repeated dose toxicity assay employed female and male mice, with oral administration of infusion or powder at the doses 250, 500 and 1000 mg/kg. The animals were evaluated for body weight, water and feed consumption, biochemical and hematological parameters, and histology of the liver, spleen, and kidneys. In vivo genotoxicity and mutagenicity (2000 mg/kg) were evaluated by the comet assay and the micronucleus test, respectively.

RESULTS

Nutritional characterization confirmed that M. oleifera leaves are rich in proteins, carbohydrates, lipids, minerals, and fiber. HPLC indicated the presence of flavonoids and cinnamic derivatives as major polyphenols. Acute toxicity did not reveal alterations in weight gain and water and feed consumptions and no change in biochemical, hematological, and histological parameters. Behavior alterations was observed in the first 2 h after administration at 5000 mg/kg in both treatments. Infusion did not present toxicity when administered for 28 days. Conversely, the powder at 500 and 1000 mg/kg promoted liver and kidney damages observed through biochemical parameters and histopathology. Genotoxicity and mutagenicity were not detected at 2000 mg/kg.

CONCLUSIONS

The present study reveals that M. oleifera leaves are an important source of polyphenols and nutrients. Indiscriminate use of both infusion and crude leaf powder above 2000 mg/kg and powder at 500 and 1000 mg/kg are not recommended. Chronic toxicological studies and establishment of preparation protocols are suggested aiming to guarantee the safety in the use of M. oleifera leaves as nutraceutical by population.

An adverse outcome pathway for lung surfactant function inhibition leading to decreased lung function

Inhaled substances, such as consumer products, chemicals at the workplace, and nanoparticles, can affect the lung function in several ways. In this paper, we explore the adverse outcome pathway (AOP) that starts when inhaled substances that reach the alveoli inhibit the function of the lung surfactant, and leads to decreased lung function. Lung surfactant covers the inner surface of the alveoli, and regulates the surface tension at the air-liquid interface during breathing. The inhibition of the lung surfactant function leads to alveolar collapse because of the resulting high surface tension at the end of expiration. The collapsed alveoli can be re-opened by inspiration, but this re-opening causes shear stress on cells covering the alveoli. This can damage the alveolar-capillary membrane integrity, allowing blood components to enter the alveolar airspace. Blood components, such as albumin, can interact with the lung surfactant and further inhibit its function. The collapse of the alveoli is responsible for a decrease in the surface area available for blood oxygenation, and it reduces the volume of air that can be inhaled and exhaled. These different key events lead to decreased lung function, characterized by clinical signs of respiratory toxicity and reduced blood oxygenation. Here we present the weight of evidence that supports the AOP, and we give an overview of the methods available in vitro and in vivo to measure each key event of the pathway, and how this AOP can potentially be used in screening for inhalation toxicity.

Evaluation of spermicidal activity of saponosides from Saponaria officinalis/Caryophyllaceae, Glycyrrhizia glabra/Fabaceae and Herniaria glabra/Caryophyllaceae

Background and objective

Chemical spermicides currently marketed and widely used are known to have many side effects. Thereby, and in order to look for more tolerated natural spermicidal agents, the aim of this work was to evaluate the spermicidal potential of saponin extracts from the roots of Saponaria officinalis/Caryophyllaceae, Glycyrrhizia glabra/Fabaceae, and Herniaria glabra/Caryophyllaceae by studying their in vitro effects on sperm mobility and vitality.

Methods

Methanolic saponin extracts from the plants roots were performed. Sperm suspensions were prepared by centrifugation on a PureSperm® density gradient (70 and 45%) and incubated with various concentrations of saponin extracts (50, 250, 500 and 750 μg/mL) at 37°C. The spermicidal activity was evaluated by studying the mobility and vitality of spermatozoa at different time intervals ranging from 10 to 240 minutes.

Results

A dose and time dependent effect on sperm mobility and vitality was observed for our extracts.

Extracts from Saponaria officinalis roots induced an irreversible immobilization and a total non-viability of sperm within 10 minutes at a concentration of 750 μg/mL. A similar effect was observed within 30 minutes at 750 μg/mL for Herniaria glabra extract and within 90 minutes at 500 μg/ml for Glycyrrhizia glabra extract.

Conclusion

The results of our study showed that the saponin extracts of our plants roots possess potent in vitro dose and time dependant spermicidal effect. These natural products could therefore represent a safer and better tolerated alternative to chemical spermicides.

Application of a unified probabilistic framework to the dose-response assessment of acrolein

BACKGROUND

In quantitative chemical risk assessment, a reference value is an estimate of an exposure to a chemical that is "likely to be without appreciable risk." Because current "deterministic" approaches do not quantitatively characterize the likelihood or severity of harm, the National Academies has recommended using reference values derived from a risk-specific dose that are treated as random variables, with probability distributions characterizing uncertainty and variability.

OBJECTIVES

In order to build familiarity and address issues needed for routine and standardized derivation of probabilistic risk-specific dose distributions, a case example applying the unified probabilistic framework presented in Chiu and Slob (2015) is developed for acrolein. This case study is based on an updated systematic evidence map of literature (Keshava et al., 2020) identifying nasal lesions reported in Dorman et al. (2008) as the most appropriate endpoint and study for reference value derivation.

METHODS

The probability distribution was calculated for the risk-specific dose, which in this implementation of the approach was calculated for the dose at which 1% of the human population is estimated to experience minimal lesions, and a probabilistic reference value was computed as the 5th percentile of this distribution. A deterministic reference value was also derived for comparison, and a sensitivity analysis of the probabilistic reference value was conducted investigating alternative assumptions for the point of departure type and exposure duration.

RESULTS

The probabilistic reference value of 6 × 10-4 mg/m3 was slightly lower than the deterministic reference value of 8 × 10-4 mg/m3, and the risk-specific dose distribution had an uncertainty spanning a factor of 137 (95th-5th percentile ratio). Sensitivity analysis yielded slightly higher probabilistic reference values ranging between 9 × 10-4 mg/m3 and 2 × 10-3 mg/m3.

CONCLUSIONS

Using a probabilistic approach for deriving a reference value allows quantitative characterization of the severity, incidence, and uncertainty of effects at a given dose. The results can be used to inform risk management decisions and improve risk communication.

Adverse outcome pathways as a tool for the design of testing strategies to support the safety assessment of emerging advanced materials at the nanoscale

Toxicity testing and regulation of advanced materials at the nanoscale, i.e. nanosafety, is challenged by the growing number of nanomaterials and their property variants requiring assessment for potential human health impacts. The existing animal-reliant toxicity testing tools are onerous in terms of time and resources and are less and less in line with the international effort to reduce animal experiments. Thus, there is a need for faster, cheaper, sensitive and effective animal alternatives that are supported by mechanistic evidence. More importantly, there is an urgency for developing alternative testing strategies that help justify the strategic prioritization of testing or targeting the most apparent adverse outcomes, selection of specific endpoints and assays and identifying nanomaterials of high concern. The Adverse Outcome Pathway (AOP) framework is a systematic process that uses the available mechanistic information concerning a toxicological response and describes causal or mechanistic linkages between a molecular initiating event, a series of intermediate key events and the adverse outcome. The AOP framework provides pragmatic insights to promote the development of alternative testing strategies. This review will detail a brief overview of the AOP framework and its application to nanotoxicology, tools for developing AOPs and the role of toxicogenomics, and summarize various AOPs of relevance to inhalation toxicity of nanomaterials that are currently under various stages of development. The review also presents a network of AOPs derived from connecting all AOPs, which shows that several adverse outcomes induced by nanomaterials originate from a molecular initiating event that describes the interaction of nanomaterials with lung cells and involve similar intermediate key events. Finally, using the example of an established AOP for lung fibrosis, the review will discuss various in vitro tests available for assessing lung fibrosis and how the information can be used to support a tiered testing strategy for lung fibrosis. The AOPs and AOP network enable deeper understanding of mechanisms involved in inhalation toxicity of nanomaterials and provide a strategy for the development of alternative test methods for hazard and risk assessment of nanomaterials.

The application of new HARD-descriptor available from the CORAL software to building up NOAEL models

Continuous QSAR models have been developed and validated for the prediction of no-observed-adverse-effect (NOAEL) in rats, using training and test sets from the Fraunhofer RepDose® database and EFSA's Chemical Hazards Database: OpenFoodTox. This paper demonstrates that the HARD index, as an integrated attribute of SMILES, improves the prediction power of NOAEL values using the continuous QSAR models and Monte Carlo simulations. The HARD-index is a line of eleven symbols, which represents the presence, or absence of eight chemical elements (nitrogen, oxygen, sulfur, phosphorus, fluorine, chlorine, bromine, and iodine) and different kinds of chemical bonds (double bond, triple bond, and stereo chemical bond). Optimal molecular descriptors calculated with the Monte Carlo technique (maximization of correlation coefficient between the descriptor and endpoint) give satisfactory predictive models for NOAEL. Optimal molecular descriptors calculated in this way with the Monte Carlo technique (maximization of correlation coefficient between the descriptor and endpoint) give amongst the best results available in the literature. The models are built up in accordance with OECD principles.

Pre-clinical toxicology of garcinielliptone FC, a tautomeric pair of polyprenylated benzophenone, isolated from Platonia insignis Mart seeds

BACKGROUND

Garcinielliptone FC (GFC) is a tautomeric pair of polyprenylated benzophenone, which has proven to have antiepileptic, cytotoxic and antioxidant activity.

PURPOSE

The aim of this study was to investigate the biochemical, hematological and pathological effects of the acute toxicity study as well as to assess the locomotor activity and motor coordination in mice treated with GFC.

METHODS

Swiss mice of both sexes weighing 25-30 g divided into three separate groups of five animals matched by weight and size. GFC was aseptically suspended in 0.05% Tween 80, dissolved in 0.9% saline (vehicle) and administered orally (p.o.) and intraperitoneally (i.p.) (500, 1000 and 2000 mg/kg). The acute toxicity study was performed in compliance with the Anvisa regulations.

RESULTS

Behavioral manifestations of toxicity, such as state of consciousness, coordination, muscle tone, reflexes, the activity on the central nervous system (shake, seizures, Straub tail reaction and anesthesia) and the activity of the autonomic nervous system (lacrimation, ptosis, urination, piloerection, hypothermia, breathing and hyperemia) were not seen in any of the animals treated with doses of 500, 1000 and 2000 mg/kg. Additionally, no significant difference in body weight, food and water intake, excreta production or macroscopic changes in the organs of treated animals were detected in comparison with control group. GFC did not affect the locomotor activity and motor coordination of the animals.

CONCLUSION

The acute toxicity study indicated that GFC treatment, at selected doses given orally and intraperitoneally, showed relatively low risk of toxicity in all test animals, suggesting that it is safe for further investigation.

EPHECT III: Health risk assessment of exposure to household consumer products

In the framework of the EU EPHECT project (Emissions, Exposure Patterns and Health Effects of Consumer Products in the EU), irritative and respiratory effects were assessed in relation to acute (30-min) and long-term (24-h) inhalation exposure to key and emerging indoor air pollutants emitted during household use of selected consumer products. A detailed Health Risk Assessment (HRA) was performed for five selected pollutants of respiratory health relevance, namely acrolein, formaldehyde, naphthalene, d-limonene and α-pinene. For each pollutant, the Critical Exposure Limit (CEL) was compared to indoor air concentrations and exposure estimates for the use of 15 selected consumer products by two population groups (housekeepers and retired people) in the four geographical regions of Europe (North, West, South, East), which were derived previously based on microenvironmental modelling. For the present HRA, health-based CELs were derived for certain compounds in case indoor air quality guidelines were not available by the World Health Organization for end-points relevant to the current study. For each pollutant, the highest indoor air concentrations in each microenvironment and exposure estimates across home microenvironments during the day were lower than the corresponding acute and long-term CELs. However, considerable contributions, especially to acute exposures, were obtained in some cases, such as formaldehyde emissions resulting from single product use of a floor cleaning agent (82% CEL), a candle (10% CEL) and an electric air freshener (17% CEL). Regarding multiple product use, the case of 30-min formaldehyde exposure reaching 34% CEL when eight product classes were used across home microenvironments, i.e. all-purpose/kitchen/floor cleaning agents, furniture/floor polish, combustible/electric air fresheners, and perfume, needs to be highlighted. Such estimated values should be evaluated with caution, as these may be attributed to the exposure scenarios specifically constructed for the present study, following a 'most-representative worst-case scenario' approach for exposure and health risk assessment.

Linkage Analysis of Urine Arsenic Species Patterns in the Strong Heart Family Study

Arsenic toxicokinetics are important for disease risks in exposed populations, but genetic determinants are not fully understood. We examined urine arsenic species patterns measured by HPLC-ICPMS among 2189 Strong Heart Study participants 18 years of age and older with data on ~400 genome-wide microsatellite markers spaced ~10 cM and arsenic speciation (683 participants from Arizona, 684 from Oklahoma, and 822 from North and South Dakota). We logit-transformed % arsenic species (% inorganic arsenic, %MMA, and %DMA) and also conducted principal component analyses of the logit % arsenic species. We used inverse-normalized residuals from multivariable-adjusted polygenic heritability analysis for multipoint variance components linkage analysis. We also examined the contribution of polymorphisms in the arsenic metabolism gene AS3MT via conditional linkage analysis. We localized a quantitative trait locus (QTL) on chromosome 10 (LOD 4.12 for %MMA, 4.65 for %DMA, and 4.84 for the first principal component of logit % arsenic species). This peak was partially but not fully explained by measured AS3MT variants. We also localized a QTL for the second principal component of logit % arsenic species on chromosome 5 (LOD 4.21) that was not evident from considering % arsenic species individually. Some other loci were suggestive or significant for 1 geographical area but not overall across all areas, indicating possible locus heterogeneity. This genome-wide linkage scan suggests genetic determinants of arsenic toxicokinetics to be identified by future fine-mapping, and illustrates the utility of principal component analysis as a novel approach that considers % arsenic species jointly.

Antinociceptive Activity and Toxicity Evaluation of the Fatty Oil from Plukenetia polyadenia Mull. Arg. (Euphorbiaceae)

Seed oil (Pp-oil) of Plukenetia polyadenia is used by native people of the Brazilian Amazon against arthritis and rheumatism, spreading it on the arms and legs to reduce the pain and inflammation. Pp-oil was obtained by pressing dried seeds at room temperature to give a 47.0% yield of oil. It was then subjected to fatty acid composition analysis. The principal fatty acids were linoleic acid (46.5%), α-linolenic acid (34.4%) and oleic acid (13.9%). Then, it was evaluated for its antinociceptive activity in mice, using the acetic acid-induced abdominal writhing, hot plate and formalin test models. Additionally, its toxicity was determined. The Pp-oil proved to have no toxicological effects, showing dose-dependent antinociceptive effect under chemical stimulation. At oral doses of 25–100 mg/kg, Pp-oil significantly reduced the abdominal writhes in the writhing test. A higher oral dose of 200 mg/kg did not induce alterations in the latency time of the hot plate test when compared to the control, suggesting an analgesic activity of peripheral origin. At oral doses of 50 and 100 mg/kg, the Pp-oil significantly reduced the second phase of the algic stimulus in the formalin test. In addition, the antinociception of Pp-oil was reversed by naloxone in the evaluation of its mechanism of action. Therefore, the Pp-oil proved to be safe at very high doses and to show significant analgesic properties. The role of Pp-oil is still being investigated with respect the mechanism of action, but the results suggest that opiod receptors could be involved in the antinociception action observed for the oil of P. polyadenia.

CARI III inhibits tumor growth in a melanoma-bearing mouse model through induction of G0/G1 cell cycle arrest

Mushroom-derived natural products have been used to prevent or treat cancer for millennia. In this study, we evaluated the anticancer effects of CARI (Cell Activation Research Institute) III, which consists of a blend of mushroom mycelia from Phellinus linteus grown on germinated brown rice, Inonotus obliquus grown on germinated brown rice, Antrodia camphorata grown on germinated brown rice and Ganoderma lucidum. Here, we showed that CARI III exerted anti-cancer activity, which is comparable to Dox against melanoma in vivo. B16F10 cells were intraperitoneally injected into C57BL6 mice to develop solid intra-abdominal tumors. Three hundred milligrams of the CARI III/kg/day p.o. regimen reduced tumor weight, comparable to the doxorubicin (Dox)-treated group. An increase in life span (ILS% = 50.88%) was observed in the CARI III-administered group, compared to the tumor control group. CARI III demonstrates anti-proliferative activity against B16F10 melanoma cells through inducing G0/G1 cell cycle arrest. CARI III inhibits the expression of cyclin D1, CDK4 and CDK2 and induces p21. Therefore, CARI III could be a potential chemopreventive supplement to melanoma patients.

A proposal for calculating the no-observed-adverse-effect level (NOAEL) for organic compounds responsible for liver toxicity based on their physicochemical properties

OBJECTIVES

Both environmental and occupational exposure limits are based on the no-observed-adverse-effect level (NOAEL), lowest-observed-adverse-effect level (LOAEL) or benchmark dose (BMD) deriving from epidemiological and experimental studies. The aim of this study is to investigate to what extent the NOAEL values for organic compounds responsible for liver toxicity calculated based on their physicochemical properties could be used for calculating occupational exposure limits.

MATERIAL AND METHODS

The distribution coefficients from air to the liver (log K(liver)) were calculated according to the Abraham solvation equation. NOAEL and LOAEL values for early effects in the liver were obtained from the literature data. The descriptors for Abraham's equation were found for 59 compounds, which were divided into 2 groups: "non-reactive" (alcohols, ketones, esters, ethers, aromatic and aliphatic hydrocarbons, amides) and "possibly reactive" (aldehydes, allyl compounds, amines, benzyl halides, halogenated hydrocarbons, acrylates).

RESULTS

The correlation coefficients between log-log K and log NOAEL for non-reactive and reactive compounds amounted to r = -0.8123 and r = -0.8045, respectively, and were statistically significant. It appears that the Abraham equation could be used to predict the NOAEL values for compounds lacking information concerning their liver toxicity.

CONCLUSIONS

In view of the tendency to limit animal testing procedures, the method proposed in this paper can improve the practice of setting exposure guidelines for the unstudied compounds.

Acute and sub-chronic toxicity of HPLC fingerprinted extract of Conyza sumatrensis (Retz.) E.H. Walker in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Conyza sumatrensis (CS) is an extensively used medicinal herb in the tropics for varied ailments related to pain, inflammation and malaria. Though in constant folkloric use, scientific validations are proving valuable.

AIM OF THE STUDY

Evaluate the safety profile of methanol extract from CS in mice and rats through acute and sub-chronic toxicity studies respectively.

MATERIAL AND METHODS

Acute toxicity study involved the single oral administration of CS at 1000, 2000 and 3000mg/kg in mice, while the sub chronic toxicity was carried upon in rats at doses 250, 500 and 1000mg/kg/day for 28 days. Besides body weight, general behaviour and mortality, serum biochemical parameters and liver histology were assessed after 7 and 28 days for acute and sub-chronic study respectively. The parameters were again checked on days 14 and 56 in order to assess the recovery from damage, if any. HPLC fingerprinting of the aqueous and methanol extract was performed through C18 column using water: acetonitrile as mobile phase with observations at 240nm.

RESULTS

In the acute toxicity test, single oral dose of 1000, 2000 and 3000mg/kg of CS did not result in any behavioural changes or mortality, indicating non toxicity. In sub-chronic toxicity studies in rats, no mortality was observed at 250, 500 and 1000mg/kg/day when administered orally for a period of 28 days. Except Serum Glutamate Pyruvate Transaminase (SGPT) level in acute study and Alkaline Phosphatase (ALP), SGPT and Serum Glutamate Oxaloacetate Transaminase (SGOT) level in sub-chronic study, all the observational, haematological and biochemical parameters studied showed non-significant changes. Histological examination of liver did not reveal any treatment-related effects in any of the studies. Moreover, haematological and biochemical changes orchestrated by CS got normalised after 14 and 56 days post-treatment in acute and sub-chronic toxicity respectively. The HPLC fingerprint could resolve 11 and 28 peaks from aqueous and methanol extracts respectively.

CONCLUSION

The experiments indicate the methanol extract to be safe even at high and repeated doses in pre-clinical studies even though the constituents are more than in aqueous extract.

Safety assessment of aqueous extract from leaf Smallanthus sonchifolius and its main active lactone, enhydrin

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson (yacon) have been used since pre-Columbian times in the Andean region to prepare medicinal herbal tea with beneficial health properties. However, there are still disagreements about the safe use. This work was carried out to evaluate the toxicity profile of both, 10% decoction of yacon leaves and their major active lactone, enhydrin.

MATERIALS AND METHODS

In vitro cytotoxicity assays were performed with Hep-G2, COS1, CHO-K1 and Vero cell lines using a test of metabolic competence based upon assessment of mitochondrial performance. In vivo toxicity study was performed in adult Wistar rats. In the acute oral toxicity each group of rats was orally given a single dose of 10% decoction or enhydrin. General condition, behavior and mortality were recorded for up to 14 days post treatment. In subchronic toxicity studies, both products were given orally for 90 days to rats. Body weight and food intakes were observed weekly. Hematological, clinical chemistry parameters and organ weight were determined in all animals at the end of the experimental period.

RESULTS

Cell viability decreased in a concentration dependent fashion when cells were incubated with 2-200 μg of 10% decoction and 0.015-7.5 μg of enhydrin. In acute study in rats, there were no deaths or signs of toxicity observed after oral administration of single doses of 10% decoction or enhydrin at any dose level up to the highest dose tested (14.0 g/kg and 0.32 g/kg, respectively). In subchronic studies in rats, both products administered orally for 90 days at daily doses of 0.07, 0.14 and 0.28 g 10% decoction/kg and 0.4, 0.8 and 8.0 mg enhydrin/kg, did not caused haematological, biochemical and histological alterations.

CONCLUSIONS

The results presented in this paper lead us to the conclusion that the use of 10% decoction and enhydrin is safe in rat at doses in which it is demonstrated the hypoglycaemic effect.

Acute and subchronic oral toxicity assessment of the herbal formula Kai-Xin-San

ETHNOPHARMACOLOGICAL RELEVANCE

Kai-Xin-San (KXS) is a famous traditional Chinese medicine (TCM) formula. It has been used in the treatment of diseases including neurasthenia, Alzheimer's disease and neurosis.

AIM OF THE STUDY

To provide information on the potential toxicity of KXS, we evaluated the acute and subchronic toxicity in rodents.

MATERIALS AND METHODS

In acute study, a single administration of KXS was given orally to mice at doses ranging from 19.67 to 60.04 g/kg. In the sub-chronic oral toxicity study, KXS was administered to rats at 0, 1, 3 and 9 g/kg for 13 weeks. Moreover, 30 days of post treatment (withdrawal study) was conducted. Mortalities, clinical signs, body weight changes, food and water consumption, haematological and biochemical parameters, gross findings and organ weights were monitored during the study period.

RESULTS

In the sub-chronic study in rats, daily oral administration of KXS at the dose of 9 g/kg/day result in significant increase in WBC, lymphocyte, alkaline phosphatase, blood sugar and significant decrease in bodyweight, serum Cre, CK and CHO at the last week of treatment. Recovery except for the body weight was observed after 30 days of post treatment.

CONCLUSIONS

KXS is relatively safe for oral medication. The LD(50) of KXS was over 32.59 g/kg for mice. The no-observed-adverse-effect-level (NOAEL) was considered to be 19.67 g/kg/day for rats.

Anti-hyperglycemic activity of chromium(III) malate complex in alloxan-induced diabetic rats

The synthesis, characterization, anti-hyperglycemic activity, oxidative DNA damage capacity, and acute toxicity of chromium(III) malate complex [Cr2(LMA)3] were described. [Cr2(LMA)3] was synthesized in a single-step reaction by chelating chromium(III) with L-malic acid in aqueous solution. Based on elemental analysis, thermodynamic analysis, and spectroscopy studies, the molecular formula of [Cr2(LMA)3] was inferred as Cr2(C4H4O5)3·5H2O. Daily treatment with 2.85-17.10 mg/kg body mass of [Cr2(LMA)3] in alloxan-induced diabetic rats for 2 weeks indicated that low-molecular-weight organic chromium complex [Cr2(LMA)3] had better bioavailability and more beneficial influences on the improvement of controlling blood glucose, serum lipid, and liver glycogen levels compared with CrCl3·6H2O. [Cr2(LMA)3] did not cause oxidative DNA damage under physiologically relevant conditions. Acute toxicity studies revealed no-measurable toxicity of the [Cr2(LMA)3]. Collectively, these results suggest that [Cr2(LMA)3] may represent a novel, proper chromium supplement with potential therapeutic value to control blood glucose and serum lipid in diabetes.

Acute airway irritation of methyl formate in mice

Methyl formate (MF) is a volatile solvent with several industrial applications. The acute airway effects of MF were evaluated in a mouse bioassay, allowing the assessment of sensory irritation of the upper airways, airflow limitation of the conducting airways and deep lung (pulmonary) irritation. MF was studied at vapour concentrations of 202–1,168 ppm. Sensory irritation was the only effect observed, which developed slowly over the 30-min exposure period. The potency at steady state was at least 10-fold higher than expected from a hypothetically similar, but non-reactive compound. Methyl formate may be hydrolysed in vivo to formic acid, a potent sensory irritant, and methanol, a low-potent sensory irritant. Hydrolysis may be catalysed by carboxyesterases, and therefore, the role of the esterases was studied using the esterase inhibitor tri-ortho-cresyl phosphate (TOCP). TOCP pre-treatment reduced the irritation response of MF, suggesting that carboxyesterase-mediated hydrolysis plays a role in the irritative effect. However, even after administration of TOCP, MF was considerably more irritating than expected from a quantitative structure–activity relationship (QSAR) model. The slope of the concentration–effect relationship for formic acid was lower than that for the MF in the low-dose range, suggesting that different receptor activation mechanisms may occur, which may include an effect of MF itself, in addition to an effect of formic acid and potentially an effect from formaldehyde.

Augmentation of humoral and cell mediated immune responses by Thujone

Thujone, a naturally occurring monoterpene, was found to enhance the total WBC count, bone marrow cellularity, number of α-esterase positive cells, number of plaque forming cells in spleen and circulating antibody titer in Balb/c mice (1mg/kg body weight, intraperitoneally for 5 days). Thujone treatment enhanced proliferation of splenocytes and thymocytes, both in the presence and absence of specific mitogens. Administration of Thujone was found to stimulate the cell-mediated immunological response in normal and tumor bearing Balb/c mice. A significant enhancement in natural killer (NK) cell mediated cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent complement mediated cytotoxicity (ACC) in both normal as well as tumor-bearing animals was observed after the administration of Thujone. Production of cytokines such as IL-2 and IFN-γ was significantly enhanced by the administration of Thujone. The stimulatory effect of Thujone on cytotoxic T lymphocyte (CTL) generation was determined by Winn's neutralization assay using CTL sensitive EL4 thymoma cells. Thujone treatment showed a significant increase in CTL production in both the in vivo and in vitro models, as indicated by a significant increase in the life span of tumor bearing animals. All these results indicate that administration of Thujone could enhance the immune response of mice. There was a significant reduction in solid tumor development, mediated by the presence of alert immune responses during Thujone administration.

Ipomoea obscura ameliorates cyclophosphamide-induced toxicity by modulating the immune system and levels of proinflammatory cytokine and GSH

Ipomoea obscura L. is a widely used medicinal plant. The objective of this study was to investigate its protective activity against cyclophosphamide (CTX)-induced toxicity in mouse models. Swiss albino mice were treated intraperitoneally with CTX (25 mg/kg body weight) along with I. obscura extract (10 mg/kg body weight) for 10 days. Extract significantly reduced myelosuppression caused by CTX and improved the relative organ weight, total white blood cell count, and bone marrow cellularity. The elevated levels of parameters related to pathophysiology of the liver, namely glutamate pyruvate transaminase, alkaline phosphatase, and lipid peroxidation, were significantly reduced by extract treatment. Reduction of liver and intestinal glutathione levels of CTX-treated animals was reversed by I. obscura. The lowered levels of cytokines, namely IFN-γ, IL-2, and granulocyte-monocyte colony-stimulating factor after CTX treatment were found to be increased in I. obscura treated animals. Treatment with I. obscura could also decrease the level of proinflammatory cytokine TNF-α. The data suggested that I. obscura can act as a potent chemoprotective agent and can be used as an adjuvant in chemotherapeutic applications.

Acute and sub-chronic oral toxicity studies of an aqueous stem bark extract of Pterocarpus soyauxii Taub (Papilionaceae) in rodents

Pterocarpus soyauxii Taub (Papilionaceae) is used in Cameroonian traditional medicine and pharmacopoeia to treat hypertension, diabetes, gastrointestinal parasitizes and cutaneous diseases.

AIM OF THE STUDY

The present investigation was carried out to evaluate the safety of an aqueous stem bark extract of Pterocarpus soyauxii by determining toxicity after acute and sub-chronic oral administration in male and female rodents.

MATERIALS AND METHODS

The acute toxicity test was conducted in mice. An aqueous extract of barks was administrated by gavage in single doses of 2.5-12.5 g/kg. General behaviour and mortality were examined for up to 7 days. The sub-chronic toxicity test was performed in rats. The plant extract was administered by daily gavage of 150-600 mg/kg for 42 days. Body weight, food and water intakes were followed weekly. Haematological, biochemical and organ parameters were determined at the end of the 42-day administration.

RESULTS

In the acute study in mice, oral administration of the aqueous extract of Pterocarpus soyauxii caused dose-dependent general behaviour adverse effects and mortality. The no-observed adverse effect level (NOAEL) of the extract was 5.0 g/kg. The lowest-observed adverse effect level (LOAEL) was 7.5 mg/kg. Mortality increased with the dose, LD(50) was>10.75 g/kg for the mouse. In the sub-chronic study in rats, daily oral administration of the aqueous extract of Pterocarpus soyauxii did not result in death or significant changes in haematological or biochemical parameters, excepted increased hepatic catalase activity (P<0.05) at the dose of 600 mg/kg. No alteration was observed in body weight, food and water intake. Liver, kidney, lung and pancreas histopathology did not reveal morphological alteration.

CONCLUSIONS

The results showed that the aqueous stem bark extract of Pterocarpus soyauxii Taub had very low toxicity in oral acute high dose administration and no toxicity in oral sub-chronic low dose administration and indicate that the plant could be considered safe for oral medication.

Antipyretic and antinociceptive effects of Nauclea latifolia root decoction and possible mechanisms of action

CONTEXT

 Nauclea latifolia Smith (Rubiaceae) is a small tree found in tropical areas in Africa. It is used in traditional medicine to treat malaria, epilepsy, anxiety, pain, fever, etc.

OBJECTIVE

 The aim of this study was to investigate the effects of Nauclea latifolia roots decoction on the peripheral and central nervous systems and its possible mechanisms of action.

MATERIALS AND METHODS

 The analgesic investigation was carried out against acetic acid-induced writhing, formalin-induced pain, hot-plate and tail immersion tests. The antipyretic activity was studied in Brewer's yeast-induced pyrexia in mice. Rota-rod test and bicuculline-induced hyperactivity were used for the assessment of locomotor activity.

RESULTS

 Nauclea latifolia induced hypothermia and had antipyretic effects in mice. The plant decoction produced significant antinociceptive activity in all analgesia animal models used. The antinociceptive effect exhibited by the decoction in the formalin test was reversed by the systemic administration of naloxone, N(ω)-L-nitro-arginine methyl ester or glibenclamide. In contrast, theophylline did not reverse this effect. Nauclea latifolia (antinociceptive doses) did not exhibit a significant effect on motor coordination of the mice in Rota-rod performance. Nauclea latifolia protected mice against bicuculline-induced behavioral excitation.

DISCUSSION AND CONCLUSION

 Overall, these results demonstrate that the central and peripheral effects of Nauclea latifolia root decoction might partially or wholly be due to the stimulation of peripheric opioid receptors through the action of the nitric oxide/cyclic monophosphate guanosin/triphosphate adenosine (NO/cGMP/ATP)-sensitive- K(+) channel pathway and/or facilitation of the GABAergic transmission.

Acute and sub-chronic toxicity of a lyophilised aqueous extract of Centaurium erythraea in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

An aqueous concoction made from centaury (Centaurium erythraea (L.) Rafn., (Gentianaceae) whole plant is used in the Moroccan traditional medicine for the treatment of diabetes, as well as a number of other diseases. No systematic study of the potential toxicity of the plant has been described.

AIM OF THE STUDY

The present investigation was carried out to evaluate the safety of an aqueous extract of Centaurium erythraea whole plant (CE-extract) by determining its potential toxicity after acute and sub-chronic administration in rats and mice.

MATERIALS AND METHODS

For the acute study, the lyophilised CE-extract was administered to adult IOPS OFA mice in single oral doses of 1-15 g/kg given by gavage, and single intraperitoneal (i.p.) doses of 1-14 g/kg. General behavioral adverse effects, mortality, and latency of mortality were determined for up to 14 days. In the sub-chronic dose study, the CE-extract was administered orally at doses of 100, 600 and 1200 mg/kg daily for 90 days to Wistar rats. Body weight and selected biochemical and hematological parameters were determined every 30 days and at the end of 90 days of daily administration; sections of liver and kidney were examined histologically for any signs of organ damage at the end of the treatment.

RESULTS

In the acute study in mice, there were no deaths or any signs of toxicity observed after oral administration of single doses of the CE-extract at any dose level up to the highest dose tested (15 g/kg), which was the no-observed-adverse-effect level (NOAEL). However, the mortality rate as well as the acute toxicity of the i.p. administered CE-extract increased progressively with increasing dose. The NOAEL for the i.p. dose was 6 g/kg while the lowest-observed-adverse-effect level (LOAEL) was 8 g/kg; the calculated acute toxicity (LD(50)) of i.p. administered CE-extract in mice was 12.13 g/kg. In sub-chronic studies in rats, the CE-extract (administered orally at daily doses of 100, 600 and 1200 mg/kg for 90 days), did not cause any changes in hematological and biochemical parameters, except a small reduction of mean corpuscular volume, and a decrease in serum glucose and triglyceride levels at the higher doses. Histopathological examination of the liver and kidneys at the end of the study showed normal architecture suggesting no morphological disturbances.

CONCLUSIONS

Because of the lack of toxicity of the CE-extract given by the oral route, and relatively high NOAEL values for the i.p. dose in the acute study in mice, as well as lack of mortality or clinically significant adverse changes in the biological and hematological parameters, and the morphology of liver and kidneys in rats after 90 days of daily dosing, it may be concluded that the CE-extract is relatively non-toxic. Also, in view of the doses consumed empirically in traditional medicine in Morocco, there is a wide margin of safety for the therapeutic use of Centaurium erythraea.

Toxicity studies of cremophor-free paclitaxel solid dispersion formulated by a supercritical antisolvent process

To evaluate the acute toxicity of a paclitaxel solid dispersion formulation, single dose studies in ICR mice were carried out for injectable excipients, paclitaxel solid dispersion powder, and Taxol. In the dose range of excipients used for preparing paclitaxel solid dispersion, each excipient was clinically safe, and the LD(50) for exicipients was higher than 2,000 mg/kg for both males and females. In this study, there were no remarkable clinical signs or deaths related to paclitaxel solid dispersion even at doses up to 160 mg/kg of paclitaxel. But Taxol resulted in clinical signs when it contained more than 30 mg/mL paclitaxel. The LD(50) for paclitaxel solid dispersion was above 160 mg/kg and the LD(50) for Taxol was 31.3 mg/kg, more than 5 times lower than that of paclitaxel solid dispersion. However, paclitaxel solid dispersion could not be administered i.v. at a dose exceeding 160 mg/kg, because of high viscosity. To evaluate the nephrotoxicity of paclitaxel solid dispersion, plasma level of creatinine and kidney weight were measured and compared to Taxol. At the doses administered, paclitaxel solid dispersion did not change creatinine clearance, while Taxol killed all animals at doses >15 mg/kg. To investigate membrane damage when paclitaxel formulations were injected, hemolytic activity was determined for different concentrations. Paclitaxel solid dispersion showed about 10% hemolytic activity, whereas Taxol showed about 40% hemolytic activity when it contained 2 mg of paclitaxel. Comparisons with the LD(50) value, nephrotoxicity, and hemolytic activity of Taxol suggested that Cremophor-free paclitaxel solid dispersion as an injectable formulation is a promising approach to increasing the safety and clinical efficacy of paclitaxel for treatment of cancer.

Acute and sub-chronic toxicity of an aqueous extract of the leaves of Herniaria glabra in rodents

AIM OF THE STUDY

The present investigation was carried out to evaluate the safety of an aqueous extract of Herniaria glabra (caryophyllaceae) (HG) plant by determining its potential toxicity after acute and sub-chronic administration in rodents.

MATERIALS AND METHODS

For the acute study, a lyophilized aqueous extract of HG plant was administered to adult IOPS OFA mice in single doses of 5-14.5 g/kg given by gavage. General behavior adverse effects and mortality were determined for up to 14 days. In the sub-chronic dose study, the HG-extract was administered orally at doses of 1, 2 and 4 g/kg daily for 90 days to Wistar rats. Selected biochemical and hematological parameters were determined after 30 and 60 days, and then at the end of 90 days of daily administration.

RESULTS

In the acute study in mice, the crude aqueous extract of HG plant caused dose-dependent general behavior adverse effects and mortality. The no-observed adverse effect levels (NOAEL) of the HG extract was 5 g/kg and the lowest-observed adverse effect levels (LOAEL) was 5.5 g/kg. Mortality increased with increasing doses: the calculated LD50 was 8.50 +/- 0.42 g/kg in mice. In the sub-chronic study in rats, daily oral administration of the crude HG extract for up to 90 days resulted in a significant attenuation of the normal increase in the body weight. At the highest dose, the HG-extract caused a significant increase in erythrocytes, leukocytes (WBC), platelets, and eosinophils, but it had no effect on the differential WBC counts (lymphocytes, monocytes, neutrophils and basophils). Only at the highest dose, the HG-extract caused a significant increase in serum levels of the liver enzymes, alanine aminotransferase and aspartate aminotransferase, as well as serum creatinine, indicating toxic effect of the high dose of the extract on the liver and kidney. The organ toxicity was confirmed by histopathological examination, which showed centrolobular sinusoidal congestion, disruption of the central vein and hepatocellular necrosis in the liver, and interstitial and intraglomerular congestion, tubular atrophy, and inflammation in the kidney. This study also revealed the hypoglycemic activity of the HG-extract in normoglycemic rats. The suppression of the normal weight gain and the hypoglycemic action of HG-extract should be investigated further for possible therapeutic implications.

CONCLUSIONS

Because of the relatively high NOAEL values in the acute study in mice, and lack of mortality or clinically significant changes in the biological (except for hypoglycemia) and hematological parameters in rats after 90 days of daily dosing, it may be concluded that the HG extract does not appear to have significant toxicity (except at high doses). In view of the doses consumed empirically in traditional medicine in Morocco, there is a wide margin of safety for the therapeutic use of Herniaria glabra.

Evaluation and application of the RD50 for determining acceptable exposure levels of airborne sensory irritants for the general public

BACKGROUND

The RD(50) (exposure concentration producing a 50% respiratory rate decrease) test evaluates airborne chemicals for sensory irritation and has become an American Society for Testing and Materials (ASTM) standard method. Past studies reported good correlations (R(2)) between RD(50)s and the occupational exposure limits, particularly threshold limit values (TLVs).

OBJECTIVE

The main purpose of this study was to examine the relationship between RD(50)s and human sensory irritation responses in a quantitative manner, particularly for chemicals that produce burning sensation of the eyes, nose, or throat, based on lowest observed adverse effect levels (LOAELs) reported for human subjects.

METHODS

We compared RD(50)s with LOAELs and acute reference exposure levels (RELs). RELs, developed by the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment, represent a level at which no adverse effects are anticipated after exposure. We collected RD(50)s from the published literature and evaluated them for consistency with ASTM procedures. We identified LOAELs for human irritation and found 25 chemicals with a corresponding RD(50) in mice.

DISCUSSION

We found the relationship between RD(50)s and LOAELs as log RD(50) = 1.16 (log LOAEL) + 0.77 with an R(2) value of 0.80. This strong correlation supports the use of the RD(50) in establishing exposure limits for the public. We further identified 16 chemical irritants with both RD(50)s and corresponding acute RELs, and calculated the relationship as log RD(50) = 0.71 (log REL) + 2.55 with an R(2) value of 0.71. This relationship could be used to identify health protective values for the public to prevent respiratory or sensory irritation.

CONCLUSION

Consequently, we believe that the RD(50) has benefits for use in setting protective levels for the health of both workers and the general population.

The application of non-default uncertainty factors in the U.S. EPA's Integrated Risk Information System (IRIS). Part I: UF(L), UF(S), and "other uncertainty factors"

The United States Environmental Protection Agency's Integrated Risk Information System (IRIS) includes hazard identification and dose-response assessment values developed by Agency scientists. Uncertainty factors (UFs) are used in the development of IRIS values to address the lack of information in five main areas. The standard UFs account for interspecies uncertainty (UF(A)) and intraspecies variability (UF(H)). The UF(A) addresses uncertainty related to the extrapolation of data from animals to humans, whereas the UF(H) addresses variability amongst individuals (i.e., intrahuman). Additional UFs have been employed to account for database incompleteness, extrapolations from a lowest-observed-adverse-effect level in the absence of a no-observed-adverse-effect level (UF(L)), and subchronic-to-chronic extrapolation (UF(S)). A sixth UF designated as "other uncertainty factors" (UF(O)) has also been applied in place of the UF(L) to account for uncertainty with the adversity of points of departure obtained using benchmark dose modeling. This review will discuss how UF(L), UF(S), and UF(O) have been applied in IRIS assessments, along with the rationale used to describe the choice of UF values that deviate from the standard default of 10.

Evaluation of acute inhalation toxicity for chemicals with limited toxicity information

A large reference database consisting of acute inhalation no-observed-adverse-effect levels (NOAELs) and acute lethality data for 97 chemicals was compiled to investigate two methods to derive health-protective concentrations for chemicals with limited toxicity data for the evaluation of one-hour intermittent inhalation exposure. One method is to determine threshold of concern (TOC) concentrations for acute toxicity potency categories and the other is to determine NOAEL-to-LC(50) ratios. In the TOC approach, 97 chemicals were classified based on the Globally Harmonized System of Classification and Labeling of Chemicals proposed by the United Nations into different acute toxicity categories (from most toxic to least toxic): Category 1, Category 2, Category 3, Category 4, and Category 5. The tenth percentile of the cumulative percentage distribution of NOAELs in each category was determined and divided by an uncertainty factor of 100 to derive the following health-protective TOC concentrations: 4microg/m(3) for chemicals classified in Category 1; 20microg/m(3) for Category 2; 125microg/m(3) for both Categories 3 and 4; and 1000microg/m(3) for Category 5. For the NOAEL-to-LC(50) ratio approach, 55 chemicals with NOAEL exposure durations < or = 24 hour were used to calculate NOAEL-to-LC(50) ratios. The tenth percentile of the cumulative percentage distribution of the ratios was calculated and divided by an uncertainty factor of 100 to produce a composite factor equal to 8.3x10(-5). For a chemical with limited toxicity information, this composite factor is multiplied by a 4-hour LC(50) value or other appropriate acute lethality data. Both approaches can be used to produce an estimate of a conservative threshold air concentration below which no appreciable risk to the general population would be expected to occur after a one-hour intermittent exposure.

Antimalarial activity of some plants traditionally used in Meru district of Kenya

Ten plant extracts commonly used by the Meru community of Kenya were evaluated for the in vitro antiplasmodial, in vivo antimalarial, cytotoxicity and animal toxicity activities. The water and methanol extracts of Ludwigia erecta and the methanol extracts of Fuerstia africana and Schkuhria pinnata exhibited high antiplasmodial activity (IC(50) < 5 microg/mL) against chloroquine sensitive (D6) and resistant (W2) Plasmodium falciparum clones. The cytotoxicity of these highly active extracts on Vero E6 cells were in the range 161.5-4650.0 microg/mL with a selectivity index (SI) of 124.2-3530.7. In vivo studies of these extracts showed less activity with chemosuppression of parasitaemia in Plasmodium berghei infected mice of 49.64-65.28%. The methanol extract of Clerodendrum eriophyllum with a lower in vitro activity (IC(50) 9.51-10.56 microg/mL) exhibited the highest chemosuppression of 90.13%. The methanol and water extracts of Pittosporum viridiflorum were toxic to mice but at a lower dose prolonged survival of P. berghei infected mice (p < 0.05) with no overt signs of toxicity. However, the extracts were cytotoxic (SI, 0.96-2.51) on Vero E6 cells. These results suggest that there is potential to isolate active non-toxic antimalarial principles from these plants.

Pharmacological studies of the aqueous extract of Sapindus trifoliatus on central nervous system: possible antimigraine mechanisms

The aqueous extract of pericarp of fruits of Sapindus trifoliatus (ST) Linn., family Sapindaceae was evaluated for its potential effects on central nervous system in mice. The extract at doses 20 and 100 mg/kg, i.p. significantly (p < 0.001) reduced the spontaneous locomotor activity and at 100 mg/kg, increased the thiopental-induced sleeping time. In rota-rod motor co-ordination test, ST at 100 mg/kg, i.p. significantly (p < 0.05-0.01) reduced the endurance time. Further ST exhibited no protection against maximal electroshock (MES)- and pentylenetetrazole (PTZ)-induced convulsions in mice. In receptor radioligand binding studies, ST exhibited affinity towards dopaminergic, alpha-adrenergic and muscarnic receptors. The findings suggest that, ST may possess principles with potential neuroleptic properties.

Acute and chronic toxicological studies of Ajuga iva in experimental animals

Ajuga iva (L.) Schreber (AI), is widely used in the Moroccan pharmacopoeia as a panacea (cure-all), and specifically for gastrointestinal disorders and diabetes, and as an anthelmintic. No toxicological investigations have been carried out on this plant. We have previously observed that single oral doses (2-14 g/kg) of a lyophilised aqueous extract of AI (AI-extract) in mice or daily oral administration of 10 mg/kg of AI-extract in rats for 2 weeks did not result in any adverse effects. We have now evaluated AI-extract for its behavioural and pharmaco-toxicological effects after acute and chronic administration by the oral and intraperitoneal routes in rats and mice. No toxicity was observed in mice after single oral doses of as high as 14 g/kg of the AI-extract. However, single intraperitoneal injections of the AI-extract (1500-5500 mg/kg BW) produced a dose-dependent increase in adverse effects in the general behaviour and the mortality rate; the LD50 of acute intraperitoneal dose was 3.6 g/kg. In chronic toxicological studies in rats, the AI-extract (administered orally at daily doses of 100, 300 and 600 mg/kg for 3 months), did not cause any changes in haematological and biochemical parameters, with the exception of a transient rise in platelet counts and a short-term decrease in serum glucose levels. Histopathological examination of the brain, liver and the kidneys at the end of the study (3 months) showed normal architecture suggesting no morphological disturbances.

Oral-to-inhalation route extrapolation in occupational health risk assessment: a critical assessment

Due to a lack of route-specific toxicity data, the health risks resulting from occupational exposure are frequently assessed by route-to-route (RtR) extrapolation based on oral toxicity data. Insight into the conditions for and the uncertainties connected with the application of RtR extrapolation has not been clearly described in a systematic manner. In our opinion, for a reliable occupational health risk assessment, it is necessary to have insight into the accuracy of the routinely applied RtR extrapolation and, if possible, to give a (semi-)quantitative estimate of the possible error introduced. Therefore, experimentally established no-observed-adverse-effect-levels for inhalation studies were compared to no-adverse-effect-levels predicted from oral toxicity studies by RtR extrapolation. From our database analysis it can be concluded that the widely used RtR extrapolation methodology based on correction for differences in (estimates of) absorption is not generally reliable and certainly not valid for substances inducing local effects. More experimental data are required (from unpublished data or new experiments) to get insight into the reliability of RtR extrapolation and the possibility to derive an assessment factor to account for the uncertainties. Moreover, validated screening methods to predict/exclude the occurrence of local effects after repeated exposure are warranted. Especially, in cases where chemical exposure by inhalation or skin contact cannot be excluded route-specific toxicity studies should be considered to prevent from inadequate estimates of human health risks.