Reaction products of sodium glucoheptonate with copper sulfate and ammonium hydroxide

Endpoint summary

Description of key information

Key study

There is a GLP compliant key study available for copper Glucoheptonate. The study was performed according to OECD Guideline 423 on rats (Wistar strain). Three sets of fasted female Wistar rats (3 females/set) (10 to 11 weeks) were given a single oral dose of copper glucoheptonate at 2000 (for set I) and 300 (for set II and set III) mg/kg body weight and all the surviving rats were observed for 14 days.

Clinical signs like lethargy were observed in rats treated with 2000 mg copper glucoheptonate/kg body weight while no clinical signs were observed in rats treated with 300 mg copper glucoheptonate/kg body weight. All rats were found dead in set I treated with 2000 mg copper glucoheptonate/kg body weight. No mortality was observed in set II and set III treated at the dose level of 300 mg copper glucoheptonate/kg body weight. Normal gain in body weight was observed in all the surviving rats. External examination of found dead and terminally sacrificed rats did not reveal any abnormality. Visceral examination of 3 rats, which were found dead revealed lesions, such as ascongestion of liver, whereas the terminally sacrificed rats did not reveal any lesions. Lesions observed in the found dead rats could be correlated with the test item used in the present study. The acute oral median lethal dose (LD50 cut-off value) of copper glucoheptonate in Wistar rats was found to be 500 mg/kg body weight. Based on the results of this study, the indication for classification of copper glucoheptonate is as follows: Globally Harmonized System of Classification and Labelling of Chemicals (GHS 2015): Category 4

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016/07/08 - 2016/07/19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

GLP compliance:

yes (incl. QA statement)

Remarks:

by National GLP compliance Monitoring Authority (NGCMA), Department of Science and Technology, Government of India

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Animal Breeding Facility, Jai Research Foundation, India
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 10 to 11 weeks
- Weight at study initiation: Minimum: 173.2, Maximum: 192.5
- Fasting period before study: overnight
- Housing: Polypropylene rat cages covered with stainless steel grid top were used. Autoclaved clean rice husk was used as the bedding material.
- Diet: Teklad Certified Global High Fiber Rat/Mice Feed manufactured by Envigo, U.S.A.
- Water: UV sterilized water filtered through Reverse Osmosis water filtration system.
- Acclimation period: 6 to 10 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 23 °C
- Humidity (%): 57 to 66%
- Air changes (per hr): Minimum 15 air changes/hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To:

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

The test item was found to be soluble in RO water, so the actual dose formulation was prepared using RO water as vehicle. Required quantity (2000 mg for set I, 300 mg for set II and set III) were mixed in RO water and the final volume was made up to 10 mL. Gavage solutions were prepared freshly prior to dosing on all the occasions.
Individual dose volume was adjusted according to body weight and dose level. All rats were dosed by oral gavage (day 0) using a BD 1 mL disposable syringe. Rats were fasted overnight prior to dosing and until three hours post-dosing.

Doses:

300 mg/kg bw and 2000 mg/kg bw

No. of animals per sex per dose:

3 females/dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of weighing and observation: The rats were observed for signs of toxicity and mortality at 0.5, 1, 2, 3, 4 and 6 hours post-administration on the day of dosing. Subsequently, the rats were observed twice a day for morbidity and mortality for a period of 14 days following oral dosing. The clinical signs were recorded once a day. Individual body weight was recorded prior to dosing on day 0 and on days 7 and 14 and at death.
- Necropsy of survivors performed: no
- Other examinations performed: clinical signs, body weight

Key result

Sex:

female

Dose descriptor:

LD50

Remarks:

rat

Effect level:

500 mg/kg bw

Based on:

test mat.

Mortality:

All rats were found dead in set I treated with 2000 mg DABQUEL COMPLEX CuP/kg body weight. No mortality was observed in set II and III rats treated at the dose level of 300 mg DABQUEL COMPLEX CuP/kg body weight.

Clinical signs:

other: Clinical sign like lethargy was observed in rats treated with 2000 mg DABQUEL COMPLEX CuP/kg body weight while no clinical sign was observed in rats treated with 300 mg DABQUEL COMPLEX CuP/kg body weight.

Gross pathology:

External
External examination of found dead and terminally sacrificed rats did not reveal any abnormality.
Internal
Visceral examination of found dead rats revealed lesion such as congestion of liver (Rat N° 1, 2 and 3) whereas the terminally sacrificed rats did not reveal any lesion. Lesion observed in the found dead rats could be correlated with the test item used in the present study.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The acute oral median lethal dose (LD50cut-off value) of DABQUEL COMPLEX CuP in Wistar rats was found to be 500 mg/kg body weight.

Executive summary:

In an acute oral toxicity study, three sets of fasted female Wistar rats (3 females/set) (10 to 11 weeks) were given a single oral dose of DABQUEL COMPLEX CuPat 2000 (for set I) and 300 [for set II and set III] mg/kg body weight and all the surviving rats were observed for 14 days.

Clinical sign like lethargy was observed in rats treated with 2000 mg DABQUEL COMPLEX CuP/kg body weight while no clinical sign was observed in rats treated with 300 mg DABQUEL COMPLEX CuP/kg body weight.

All rats were found dead in set I treated with 2000 mg DABQUEL COMPLEX CuP/kg body weight. No mortality was observed in set II and set III treated at the dose level of 300 mg DABQUEL COMPLEX CuP/kg body weight.

Normal gain in body weight was observed in all the surviving rats.

External examination of found dead and terminally sacrificed rats did not reveal any abnormality. Visceral examination of found dead rats revealed lesions such as congestion of liver (Rat N° 1, 2 and 3) whereas the terminally sacrificed rats did not reveal any lesion. Lesion observed in the found dead rats could be correlated with the test item used in the present study.

The acute oral median lethal dose (LD50cut-off value) of DABQUEL COMPLEX CuP in Wistar rats was found to be 500 mg/kg body weight.

Based on the results of this study, an indication of the classification for DABQUEL COMPLEX CuP is as follows:

Globally Harmonized System of Classification and Labelling of Chemicals (GHS 2015): Category 4

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

500 mg/kg bw

Quality of whole database:

The quality of the whole database is high since a key study with copper glucoheptonate and numerous weight of evidence studies for organic and inorganic copper compounds are available.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Read-across approach

To underline the results of the key study, read-across was performed. Copper glucoheptonate is a chelate compound consisting of two molecules of sugar like glucoheptonic acid and two copper ions. Since the toxicity of copper glucoheptonate is believed to be mediated by excess exposure of living organisms to elemental copper, toxicity studies with inorganic and organic copper compounds have been taken into account. Toxicity studies with glucoheptonates (calcium and magnesium) and gluconates (a structural analogue of glucoheptonate) have also been included to the endpoint to show toxicity potential originating from glucoheptonate anion (please refer to read-across statement attached in section 13). A rat-study with copper gluconate (Abe et al., 2008) is considered as the most reliable for the evaluation of acute oral toxicity of copper glucoheptonates. However, since all studies have certain defficiencies (no GLP, no guideline followed, no clear study protocol or others), all availabel information is taken into account for hazard assessment.

Acute oral toxicity of the nearest analogue substance copper gluconate

In the Handbook of Preservatives (Ash and Ash, 2004), a LD50 (oral, rat) of 1710 mg/kg bw is reported for copper gluconate (Gluconal ®CU).

The acute toxicity of copper gluconate was assessed during the course of medium-term liver carcinogenicity bioassay protocol (Ito test) and a 2-week short-term administration experiment (Abe et al., 2008). In the medium-term liver bioassay, two control groups of Fischer rats were fed the diets containing copper gluconate at concentrations of 0 and 6,000 ppm. The effects observed in these two groups are relevant for the assessment of acute oral toxicity. All rats underwent 2/3 partial hepatectomy at the end of week 3, and all surviving rats were killed at the end of week 8. In the short-term experiment, rats were given 0, 10, 300 or 6,000 ppm of copper gluconate for 2 weeks. The effects reported in short-term experiment are also relevant for the assessment of acute oral toxicity.

Food consumption and body weight were recorded weekly for all groups in two experiments. Livers were analysed macroscopically and histopathologically. Additionally, immunohistochemical examinations (staining for GST-P-positive foci of cellular alteration; 8-oxoG, proliferating cell nuclear antigen (PCNA), terminal deoxynucleotidyl transferase-mediated dUTPbiotin nick end-labelling (TUNEL) and real-time quantitative RT-PCR analysis were performed).

In the following, the only effects reported in rats of two control groups (treated with 6000 ppm copper gluconate in feed) in medium-term liver carcinogenicity bioassay experiment as well as results reported in rats from short-term experiment are summarised.

No mortality is reported either in medium-term liver carcinogenicity bioassay (groups 5 and 6) or in short-term experiment at all dose levels tested. In medium-term liver carcinogenicity bioassay experiment, final body weight and absolute liver weight were significantly decreased in the group given copper gluconate at 6,000 ppm, but relative liver weights were not significantly different from the control group (fed basal diet). Food consumption was also not significantly decreased. In contrast, final body weight, liver weight or food consumption was not affected by copper gluconate in the short-term experiment. In medium-term liver carcinogenicity bioassay experiment, the livers were macroscopically normal in rats treated with 6000 ppm copper gluconate, whereas apoptotic bodies were observed. No copper gluconate- related alterations were detected either macroscopically or histologically in the liver of any animals in the short-term experiment. GST-P-positive single hepatocytes were significantly increased by 6,000 ppm of copper gluconate, whereas they were not observed in untreated control group (medium-term liver carcinogenicity bioassay protocol).

In conclusion, the dose level of 6000 ppm of copper gluconate in feed (equivalent to 442.81 ± 11.95 mg/kg bw (62.00 ± 1.67 mg Cu/kg bw)) did not produce mortalities in Fischer 344 rats in both experiments. Liver toxicity was observed at this dose level. The dose level of 6000 ppm in feed can be considered as short-term LOAEL for rats.

Acute oral toxicity of glucoheptonates

No toxicity can be attributed to glucoheptonate anion. Calcium glucoheptonate has been used for decades in both human and veterinary medicine for treatment of hypocalcaemia to correct calcium deficiency states (EMEA, 1998; Drop and Cullen, 1980). Therefore, no classical toxicity studies were carried out with calcium glucoheptonate in laboratory animals. In human medicine, the normal dose is intended to provide 50 mmol of calcium daily (equivalent to 25 g/day of calcium glucoheptonate). In cases of hypocalcaemia, parenteral administration of 2.25 to 4.5 nmol calcium (equivalent to 1.125 to 2.25 g/day of calcium glucoheptonate) may be given and repeated as necessary (EMEA, 1998).

In addition, glucoheptonates are widely used as imaging agents in nuclear medicine (please refer to read-across statement).

Acute oral toxicity of magnesium glucoheptonate is reported in a US patent (1962) dealing with methods employing this pharmaceutical. LD50 of 21,260 and 18,170 mg/kg bw were determined for white mouse and rat, respectively.

Acute oral toxicity of gluconates and its derivatives

Gluconate ion differs from glucoheptonate by one carbon increment (HC-OH) and therefore the substances are believed to be involved in similar metabolic carbohydrate pathways in mammals (please refer to read-across statement). For this reason, acute toxicity data on gluconic acid and its derivatives have been taken into account to assess acute toxicity data of glucoheptonate anion.

Gluconic acid and its derivatives are naturally occurring substances. In mammalian organisms both D-gluconic acid and 1,5-lactone are important intermediates in the carbohydrate metabolism. Gluconate is a metabolite of glucose oxidation. The daily production of gluconate from endogenous sources is about 450 mg/kg for a 60 kg person (SIDS, 2004).

There is also considerable experience with the comparatively low toxicity of gluconate to man and animals. Glucono-delta-lactone and gluconic acid were not toxic to animals and humans when given at very high dose levels (> 2000 mg/kg bw). When three men were given 10 g (167 mg/kg) of glucono-delta-lactone orally as a 10 % solution, the amounts recovered in the urine in 7 hours represented 7.7-15 % of the dose. No pathological urine constituents were noted. When 5 g (84 mg/kg) was given orally, none was recovered in the urine. The largest dose given to man was 30 g (500 mg/kg) (Chenoweth et al., 1941, cited in WHO, 1966).The administration for 3-6 days of large oral doses (5-10 g/day) of gluconic acid to five normal humans did not produce any renal changes, as by the absence of blood, protein, casts and sugar in the urine (Chenoweth et al., 1941, cited in WHO, 1966 and WHO, 1999). Oral LD50 for animal species are reported: 5940, 6800, 7850 and 5600 mg/kg bw in rats, mice, rabbits and hamsters, respectively (WHO, 1966; WHO, 1999). In several further acute oral toxicity studies with sodium gluconate, no deaths were observed at any dose level tested in rats and dogs, therefore LD50 values of greater than 2000 mg/kg bw were reported for both species (Mochizuki, 1995; Okamoto, 1995; SIDS, 2004). A gavage study with potassium gluconate and rats reported an LD50 of 6060 mg/kg bw (TNO, 1978, cited in SIDS, 2004). LD10 of 10,000 mg/kg bw is reported for calcium gluconate in rats (RTECS, 1978; Sarabia et al., 1999).

Acute oral toxicity of copper compounds

Human data

Human data on the acute effects of copper include case-reports of self-poisoning or accidental ingestion of high doses of copper-containing compounds, case reports of parenteral exposure via contaminated dialysate, reports concerning metal-fume fever, and two well-controlled clinical studies (WHO, 2004).

One of the most commonly reported adverse health effect of copper is gastrointestinal distress (ATSDR, 2004). Metallic taste, epigastric burning, nausea, vomiting, and/or abdominal pain have been reported, usually occurring shortly after drinking a copper sulfate solution, beverages that were stored in a copper or untinned brass container, or first draw water (water that sat in the pipe overnight). The observed effects are not usually persistent and gastrointestinal effects have not been linked with other health effects. Animal studies have also reported gastrointestinal effects (hyperplasia of forestomach mucosa) following ingestion of copper sulfate in the diet. Copper is also irritating to the respiratory tract. The liver is also a sensitive target of toxicity. Liver damage (necrosis, fibrosis, abnormal biomarkers of liver damage) have been reported in individuals ingesting lethal doses of copper sulfate. In more severe cases, lethargy, haemolytic anaemia, damage of liver and kidney as well as sometimes coma and death have been reported (SCOEL, 2013). Liver effects have also been observed in individuals diagnosed with Wilson’s disease, Indian childhood cirrhosis, or idiopathic copper toxicosis (which includes Tyrollean infantile cirrhosis). These syndromes are genetic disorders that result in an accumulation of copper in the liver; the latter two syndromes are associated with excessive copper exposure. Inflammation, necrosis, and altered serum markers of liver damage have been observed in rats fed diets with copper sulfate levels that are at least 100 times higher than the nutritional requirement. Damage to the proximal convoluted tubules of the kidney has also been observed in rats. The liver and kidney effects usually occur at similar dose levels; however, the latency period for the kidney effects is longer than for the liver effects.

WHO have concluded that the fatal oral dose of copper salts is about 200 mg/kg body weight (WHO, 1993). Tolerable upper intake level (from all sources) of 5 mg Cu /day is derived (SCF, 2006).

Based on the the median intake from food (US) of 0.93– 1.3 mg/day for adults (0.013–0.019 mg Cu/kg body weight/day using a 70-kg reference body weight), a recommended dietary allowance (RDA) of 0.9 mg/day (0.013 mg/kg/day) has recently been established. Minimal Risk Level (MRL) of 0.01 mg/kg/day has been derived for acute-duration oral exposure (1–14 days) to copper for humans (ATSDR, 2004).

Ingestion of large amounts of copper sulphate, as in cases of self-poisoning, is associated with severe hepatotoxicity, nephrotoxicity and gastrointestinal effects, in several cases resulting in fatalities. Such reports of copper sulphate ingestion do not enable a NOAEL to be derived (EU VRAR, 2007).

The most reliable studies for the determination of a NOAEL for adults are two well-controlled, internationally diverse volunteer studies in which copper (as copper sulphate) was administered as a single dose in drinking water (Araya et al., 2001; Araya et al., 2003). Both studies reported a concentration-related increase in gastrointestinal symptoms associated with single oral exposure to copper in drinking water, the earliest and most frequently reported symptom being nausea. In both of these studies, the NOAEL for gastrointestinal symptoms in adults was a concentration of 4 mg/L copper in drinking water (0.8 mg Cu); the LOAEL was 6 mg/L copper in drinking water (1.2 mg Cu). These values were the same for a female study population or a male and female combined study population.

Animal data

In animals, oral LD50 values for various copper salts are in the range of 15–857 mg/kg bw, depending on the species and the compound (SCOEL, 2013). Water soluble salts are generally more toxic than compounds with lower solubility (EU VRAR, 2007). Symptoms in these studies included salivation, vomiting, diarrhoea, gastric haemorrhage, hypotension, haemolytic crisis, convulsions and paralysis.

Since the target substance copper glucoheptonate is a very soluble substance, data on soluble copper sulphate has been considered to be appropriate for the read-across purposes. The reported LD50 values for copper sulphate pentahydrate range from 482 - 960 mg/kg bw in rats (EU VRAR, 2007). The report cites the most reliable data on the acute oral toxicity of copper sulphate from unpublished studies by Lehritier (1994) and Manciaux (1998). “In the study by Lehritier (1994), copper sulphate (>99% purity) administered in water had a LD50 value in rats of 482 mg/kg bw (male and female combined). Clinical signs of toxicity included subdued behaviour and diarrhoea. Manciaux (1998) reported a slightly higher LD50 value of 666 mg/kg bw in female rats with copper sulphate (purity not reported; copper content 25.4% w/w), also administered in water. Clinical signs of toxicity included sedation, hypoactivity, dyspnoea, convulsions and lateral incumbency. Both studies were conducted according to Annex V (B.1) and/or OECD (401) methods. Published data on the acute oral toxicity of copper sulphate are considered less reliable as studies were not conducted according to Annex V methods (Lehman 1951; Smyth et al, 1969)” (EU VRAR, 2007).

Derivation of a LD50 for copper glucoheptonate

Solubility of copper compounds is reported to be an important factor for acute oral toxicity (EU VRAR, 2007). Since copper glucoheptonate is a very soluble substance, acute toxicity data on the nearest analogue copper gluconate and on soluble copper sulphate have been taken for the estimation of a LD50 for copper glucoheptonate.

The toxicity of glucoheptonate anion is negligible. It was evident from acute toxicity studies with magnesium glucoheptonate in which LD50 of 21,260 and 18,170 mg/kg bw were determined for white mouse and rat, respectively (US Patent, 1962). Therefore, the toxicity of copper compounds is believed to be driven by copper cation. In this regard, the most reliable data from literature on acute toxicity dose levels of elemental copper have been used to esimate a corresponding LD50 for copper glucoheptonate.

Short-term (2 week) LOAEL of 442.81 mg/kg bw (corresponds to 62 mg Cu/kg bw) was established for copper gluconate in course of a medium-liver carcinogenicity bioassay protocol in rats (Abe et al., 2008).

Based on molecular weight (MW) of 651.1 g/mol (dihydrated form; Polyhedron, 1955), and taking into account that 2 Cu (MW of 63.55 g/mol) ions chelate 2 molecules of glucoheptonic acid, 62 mg Cu/kg bw would correspond to short-term LOAEL of 317.6 mg/kg bw for copper glucoheptonate.

In another acute oral toxicity study with rats, LD50 of 482 mg/kg bw was determined for Cu sulphate pentahydrate (EU VRAR, 2007).

Mol. Weight of CuSO4 x 5 H2O (copper sulphate pentahyrdate): 249.685 g/mol

Mol weight of Copper is 63.5 g/mol.

It means that 482 mg of CuSO4 x 5 H2O contains 122.7 mg Cu: (482 x 63.5)/ 249.7.

Providing, if Cu glucoheptonate was tested in an acute oral study, the toxicity would depend on systemically available copper. Extrapolating 122.7 mg of copper to copper glucoheptonate, and taking into account that 2 Cu ions chelate 2 molecules of glucoheptonic acid (MW of the complex is 651.1 g/mol, the corresponding quantity of Cu glucoheptonate is 628 mg/kg bw:

(651.1 x 122.7) /(63.55 x 2).

Since estimation of the LD50 is already based on LD50 value in rats, no additional correction for gastrointestinal absorption* rate is considered necessary. Assuming that absorption rates in rats and in humans are the same, LD50 would result in 897.1 mg/kg bw for copper glucoheptonate.

The estimated 2-week LOAEL of 317.6 mg/kg bw and the estimated LD50 of 628 mg/kg bw correlate well with each other. The LD50 value however is relevant for classification and labelling purposes.

Both values have been calculated using stoichiometric relationship of molecular weight of copper glucoheptonate. It contains 19.5 % copper ((63.55 x 2) x 100 %)/ 651.1). According to the specifications, the product contains however 13 % copper. The chelated fraction of copper is nearly 95 % in the product. The absorption pattern of 5 % unchelated copper is considered not to deviate substantially from the absorption pattern of the chelated copper. Therefore, the assumption is that 100 % of copper is chelated. Based on 13 % copper in the product, LD50 of 122.7 mg Cu/kg bw (based on copper sulphate pentahydrate study) would correspond to 943.7 (rounded to 944) mg/kg bw product containing copper glucoheptonate. It is also known that the purity of the substance copper glucoheptonate in the product is 70 %. Then, the estimated LD50 of 628 mg/kg bw would correspond to 897 mg/kg bw of the registered product copper glucoheptonate.

Based on the reported LD50 of 1710 mg/kg bw for copper gluconate (Ash ans Ash, 2004 in Handbook of preservatives), as the most structurally similar substance to copper glucoheptonate, a corresponding theoretical LD50 for Copper glucoheptonate would be 1752 mg/kg bw:

1) Based on MW of 453.8 g/mol (anhydrous form) for Copper gluconate and that one atom of copper is chelated by two gluconate ions, 1710 mg of copper gluconate contains 239.5 mg copper: ((1710 x 63.55)/ 453.8);

2) For sodium copper glucoheptonate complex (HGA:Cu as 1:1) with MW of 651.1 g/mol, 239.5 mg copper would correspond to 1226.7 mg of copper glucoheptonate: ((651.1 x 239.46)/ (63.55 x 2).

Taking into account the fact that the content of copper glucoheptonate complex is about 70 % in the product, 1226.6 mg of copper glucoheptonate would correspond to 1752.4 mg/kg bw of the registered product.

* With regard to copper absorption via gastrointestinal tract (based on inorganic and organic copper compounds):

Copper is an essential element, which is incorporated in various proteins. It is a constituent of more than 20 enzymes (SCOEL, 2013). Physiologically normal levels of copper in the body are held constant by alterations in the rate and amount of copper absorption, compartmental distribution, and excretion (ATSDR, 2004). The site of maximal copper absorption is not known for humans, but it is assumed to be the stomach and duodenum; the average absorption efficiencies ranged from 24 to 60 % in presumably healthy adults. Copper is absorbed from the gastrointestinal tract as ionic copper or bound to amino acids or binding proteins (metallothionein). Numerous factors may affect copper absorption. These factors include: the amount of copper in the diet, competition with other metals, including zinc, iron, and cadmium and age (ATSDR, 2004). The absorption of copper appears to be inversely related to the amount of copper in the gastrointestinal tract (ATSDR, 2004).

The complex copper glucoheptonate is expected to dissociate at high acidic conditions of stomach (pH of 1-3). However in upper intestines, where pH raises, copper cation will tend to be complexed again with free ligand glucoheptonate. On the other hand, free glucoheptonate is expected to be completely absorbed in the intestines or undergo primary enzymatic destruction in stomach. Thus, the absorbed fraction will result from intact copper glucoheptonate and its released components: Cu2+ ions and free glucoheptonate. Intestinal uptake of released Cu2+ ions is moderate (60 %), while intestinal uptake of glucoheptonate is assumed to be 100 %. Moreover, the uptake of Cu ions is expected to be high in presence of glucoheptonate. This argument is supported by data on absorption, transport and metabolism of Cu reported by Cousins et al. (1985). Absorption of Cu is more easily in the presence of citrate, phosphate, gluconate or other naturally and synthetic (like EDTA) occurring complexes (Cousins et al., 1985). These data are in agreement with findings of Harrisson et al. (1954), who found that the toxicity of copper gluconate was even slightly more pronounced than the toxicity of copper sulfate in a life cycle study in rats. The adverse effects of copper as gluconate was the most marked on growth, organ weights and liver histopathology (Harrisson et al., 1954).

Based on these data, it can be concluded that considerable amounts of copper glucoheptonate are expected to cross gastrointestinal tract epithelium in case of oral exposure.

Justification for classification or non-classification

The oral LD50 value of 500 mg/kg bw that is based on the acute toxicity study with copper glucoheptonate on rats according to OECD Guideline 423 leads to a classification of copper glucoheptonate into Cat 4 (H302: Harmful if swallowed) taking into account the provisions laid down in Council Directive 67/548/EEC and CLP Regulation (EC) No 1272/2008.