Tetrahydro-4-methyl-2-(2-methylprop-1-enyl)pyran

Endpoint summary

Description of key information

Repeated dose toxicity – oral:  subchronic study; rat, feed; OECD TG 408, GLP (BASF 50C0087/18S026): 
NOAEL (male) = 12 000 ppm (1547 mg/kg bw/day); 
NOAEL (female) =  12 000 ppm (1620 mg/kg bw/day) 

Additional information

Repeated dose toxicity after oral administration

In the key study for repeated dose toxicity, i.e. an oral subchronic toxicity study in rats according to OECD TG 408 and GLP, tetrahydro-4-methyl-2-(2-methylprop-1-enyl)pyran (termed as Rose oxide 90 (encapsulated)) has been administered in alginate microcapsules via the diet (BASF 50C0087/18S026). Rose oxide 90 (encapsulated) was administered to groups of 10 male and 10 female Wistar rats at concentrations of 0 ppm (pure maintenance diet), 0 ppm (Placebo Alginate – without Rose oxide 90), 7500 ppm, 25000 ppm and 75000 ppm over a period of 3 months. Based on a content of about 16% pure Rose oxide 90 in the alginate capsule material, the effective concentrations of Rose Oxide 90 (a.i.) were 0 ppm, 0 ppm, 1200 ppm, 4000 ppm and 12000 ppm, respectively. To achieve a constant concentration of alginate capsules in the diet of test substance groups, Placebo Alginate without Rose oxide 90 was supplemented.

Food consumption and body weight were determined weekly. The animals were examined for signs of toxicity or mortality at least once a day. Detailed clinical examinations in an open field were conducted prior to the start of the administration period and weekly thereafter. Ophthalmological examinations were performed before the beginning and towards the end of the administration period. Beside this, a functional observational battery as well as measurement of motor activity were carried out towards the end of the administration period. Clinico-chemical and hematological examinations as well as urinalyses were performed towards the end of the administration period. After the administration period all animals were sacrificed and assessed by gross pathology. Organ weights were determined followed by histopathological examinations.

Regarding clinical observations, no findings of toxicological relevance were obtained. In mid and high dose male animals, mean body weight changes were significantly lower and the feed uptake was assumed to be reduced because of palatability problems. However, food consumption values could not be determined properly, due to intense food spilling by male and female animals of the mid and high dose groups. A direct and relevant toxic effect of Rose oxide 90 resulting in reduced food consumption and lowered body weight development was considered less likely since no relevant changes were obtained for clinical pathology and pathology parameters. Concerning clinical pathology, no treatment-related, adverse effects were observed up to a concentration in the diet of the active ingredient Rose oxide 90 of 12000 ppm (i.e. encapsulated Rose oxide 90 of 75000 ppm). Regarding pathology, there were neither substance-related organ weight deviations nor gross lesions. Histopathological findings occurred either individually or were biologically equally distributed over untreated control, placebo and treatment groups. They were considered to have no relation to treatment.

In conclusion, the administration of Rose oxide 90 via the diet to male and female Wistar rats for 3 months did not cause any test substance-related, adverse signs of toxicity in male and female animals up to a concentration in the diet of encapsulated Rose oxide 90 of 75000 ppm (i.e. 12000 ppm Rose Oxide 90 as active ingredient). Therefore, under the conditions of the present study the no observed adverse effect level (NOAEL) was 75000 ppm (12000 ppm a.i.) in male (1547 mg/kg bw/d) and female (1620 mg/kg bw/d) Wistar rats.

 

In a further repeated dose toxicity study in rats, i.e. a subacute oral toxicity study according to OECD TG 407 and GLP, tetrahydro-4-methyl-2-(2-methylprop-1-enyl)pyran (Rose oxide 90) was applied orally via gavage to rats (BASF 30C0624/07S043, 2012). Rose oxide 90 in corn oil was administered to Wistar rats by gavage (groups of 5 male and female rats) at concentrations of 0 (group 0), 100 (group 1), 300 (group 2) and 1000 mg/kg bw/day (group 3) over a period of 4 weeks.

There were no treatment-related significant changes in clinical examinations, body weight, food consumption and water consumption. The moderate salivation observed in animals of both sexes after application of Rose oxide 90 was induced by a bad taste of the test substance or local affection of the upper digestive tract and therefore not an adverse and toxicologically relevant effect. A slight anemia was present after 4 weeks of compound administration in high dose male and female rats.

Identified target organs were the epididymides in males as well as the liver, kidneys and spleen in males and females.

In high dose female rats, liver cell membranes as well as the liver cell metabolism was affected, indicated by increased alanine aminotransferase (ALT) activities and higher triglyceride and cholesterol values. Significant absolute and relative liver weight increases occurred in all mid dose (300 mg/kg bw/d) and high dose (1000 mg/kg bw/d) animals, without a histopathological correlate. Nevertheless, the liver weight increment was regarded as treatment-related but not adverse in nature.

In a metabolome analysis with mid and high dose treated rats, assessing a plasma profile with 272 endogenous metabolites, matches for liver toxicity, paracetamol-induced toxicity, liver enzyme induction and indirect effects on the thyroid were identified in female animals, when compared to the metabolite patterns for different toxicological modes of action available in the MetaMap®Tox database (BASF 97Z0624/07K080). In contrast, no matches or weak matches were obtained for male animals. These data support the conclusion, that the treatment with tetrahydro-4-methyl-2-(2-methylprop-1-enyl)pyran (Rose oxide 90) lead to an induction of liver enzymes which has the potential for an increased metabolism of thyroid hormones. This mode of action was prominently observed for female animals but not for male animals.

Histopathological examinations revealed adverse effects in the left epididymis. Immature ducts were present in the distal corpus and/or cauda epididymis in all mid and high dose males (300 and 1000 mg/kg bw/d) and increased in severity by ranging from minimal to slight in the mid dose group up to severe effects in high dose animals. With increasing severity, the immature ducts were accompanied by increasing interstitial edema, which correlated with the significant weight increase found in high dose animals. In only two of five high dose males, additional intraductal granulocytic infiltration was observed in single distended ducts of the cauda with apparent sperm stasis.

In the spleen slight extramedullary hematopoiesis was seen in high dose males and females (1000 mg/kg bw/d). This finding correlated with the significant relative weight increase of the spleen in males (36%) and with the non-significant spleen weight increase in females (absolute: 20%; relative: 19%). The extramedullary hematopoiesis was considered secondary to the anemia detected at hematology and was regarded as an adaptive response.

No histopathological findings were detected in the kidneys of males and females that could explain their weight increase in the two upper dose groups (300 and 1000 mg/kg bw/d), which was therefore regarded as treatment-related but not adverse. No treatment-related effects were seen in males and females of the low dose test group (100 mg/kg bw/d). Therefore, the no observed adverse effect level (NOAEL) was set at 100 mg/kg bw/d in male and 300 mg/kg bw/d female Wistar rats.

 

In a 90-day subchronic study from literature not according to current test guidelines, groups of 10-16 CD rats/sex were treated by dietary administration while the control groups were given the basic diet alone (Posternak et al. 1969). Body weights were recorded weekly and food consumption calculated on a weekly basis. The average dietary intake of the test material in males was 2.51 mg/kg bw/d, and in females it was 2.81 mg/kg bw/d. Hematology, blood urea levels, liver and kidney weights, gross- and histopathological examinations were performed. No deaths occurred. The food intake and efficiency of food utilization were not affected. A non-significant decrease in bodyweight gain was exhibited. No significant changes were observed in clinical chemistry hematology parameters, organ weights and organ pathology.

 

Repeated dose toxicity after dermal administration

There are no data available.

 

Repeated dose toxicity after inhalation

There are no data available

Justification for classification or non-classification

The present data on repeated dose toxicity do not fulfill the criteria laid down in regulation (EU) 1272/2008, and therefore, a non-classification is warranted.