Methyl α-D-mannopyranoside

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics, other

Remarks:

expert statement

Type of information:

other: expert statement

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: expert statement based on physical/chemical and toxicology properties, no study on toxicokinetics available

Principles of method if other than guideline:

Expert statement

GLP compliance:

no

Details on absorption:

Absorption is a property of a substance to diffuse across biological membranes. Generally, oral absorption is favored for molecular weights below 500 g/mol and log Pow values between -1 and 4. The good water solubility of 324.3 to 329.3 g/L enables the substance to dissolve in the gastrointestinal fluids. In combination with the low molecular weight of less than 200 g/mol the test substance can pass through aqueous pores or can be carried through the epithelial barrier by the bulk passage of water. The log Pow value shows that passive diffusion is unlikely. Taken together, the physiochemical properties indicate that the test substance becomes bioavailable following the oral route. This assumption is neither confirmed nor rebutted by the results of an acute toxicity study and a 14-day range finding study conducted with the test substance, as no mortality, effects on body weight, gross pathology and haematology or clinical signs have been reported after acute or repeated oral administration to rats.

Due to the melting point of the substance above 70 °C, no availability as a vapour under standard environmental conditions is expected. Still the vapour pressure was determined and is very low. It is 3.7E-4 Pa at 20 °C. As the substance is a powder formation and inhalation of dusts might occur. Generally particles with an aerodynamic diameter below 100 μm have the potential to be inspired, below 50 μm may reach the thoracic region and those below 15 μm can pass into the alveolar region of the respiratory tract. The test substance consists of only ca. 40 % particles smaller or equal to 100 μm (ca. 14 % smaller than 15 μm and ca. 25 % below 50 μm). As demonstrated by the distribution of the particle size the inhalable amount of the test substance is low and less than 15 % of the substance’s particles might possess the ability to reach the alveolar region. Deposited substance can potentially passage through aqueous pores or be carried across membranes with the bulk passage of water, while passive diffusion is less likely due to the low log Pow determined for the substance.

As a powder, the substance is not readily taken up by the skin. However, once moistened on the skin surface, absorption is possible, due to the high water solubility determined for the test substance. The molecular weight (194 g/mol) of the substance neither favours nor excludes dermal uptake. Considering the low log Pow between -3.2 and -2.9 of the test substance, the substance is likely to be too lipophobic to cross the stratum corneum, resulting in low dermal absorption.

Details on distribution in tissues:

As mentioned above, the physicochemical properties of the test substance favour systemic absorption following oral, inhalative and dermal uptake to a certain extent.
Direct transport through aqueous pores is likely to be an entry route to the systemic circulation. After being absorbed into the body, the substance is most likely not distributed into the interior part of cells due to the hydrophilic properties (log Pow between -3.2 and -2.9) and in turn the extracellular concentration is expected to be higher than intracellular concentration. The test substance does not have a bioaccumulative potential. The log Pow of the test substance indicates no bioaccumulation potential, as it is well below 3.

Details on excretion:

In general, urinary excretion in favored by low molecular weight (below 300 g/mol in the rat) and good water solubility. Therefore, the test substance is expected to be excreted mostly via urine.

Details on metabolites:

The genotoxicity studies with the test substance indicate no remarkable differences in regard to genotoxicity and cytotoxicity in the presence or absence of metabolic activation systems. Thus, no metabolic activation is expected. Generally it is likely that common protein interaction such as cytochrome P450 oxidases interaction during Phase I metabolism introduce a reactive or polar group in the substance. The resulting compounds might be further processed into polar compounds during the metabolism in Phase II.

Conclusions:

Bioaccumulation of the test substance is not considered critical based on an expert statement.

Executive summary:

No experimental data on absorption, distribution, metabolism and excretion are available for the substance. Based on physicochemical characteristics, particularly water solubility, molecular weight and octanol-water partition coefficient, systemic absorption following oral, inhalative and dermal uptake is favoured to a certain extent. Bioaccumulation of the test substance is not considered critical, as log Pow of the test substance indicates no bioaccumulation potential. Phase I and II metabolism within liver cells with involvement of cytochrome P450 is likely and excretion will presumably occur after renal passage via urine.

Description of key information

No experimental data on absorption, distribution, metabolism and excretion are available for the substance. Based on physicochemical characteristics, particularly water solubility, molecular weight and octanol-water partition coefficient, systemic absorption following oral, inhalative and dermal uptake is favoured to a certain extent. Bioaccumulation of the test substance is not considered critical, as log Pow of the test substance indicates no bioaccumulation potential. Phase I and II metabolism within liver cells with involvement of cytochrome P450 is likely and excretion will presumably occur after renal passage via urine (reference 7.1.1-1).

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Toxicokinetic assessment

The test substance is a solid powder with a molecular weight of 194 g/mol. The test item has good water solubility in the range of 324.3 to 329.3 g/L at 20 °C. The log P_ow is estimated to be between -3.2 and -2.9 and the vapour pressure is 3.7E-4 Pa at 20 °C. The substance melts at 193.3 °C and starts boiling at 253 to 267 °C. The median particle size (D50) is 145.0 µm.

 

Absorption

Absorption is a property of a substance to diffuse across biological membranes. Generally, oral absorption is favored for molecular weights below 500 g/mol and log P_ow values between -1 and 4. The good water solubility of 324.3 to 329.3 g/L enables the substance to dissolve in the gastrointestinal fluids. In combination with the low molecular weight of less than 200 g/mol the test substance can pass through aqueous pores or can be carried through the epithelial barrier by the bulk passage of water. The log Pow value shows that passive diffusion is unlikely. Taken together, the physiochemical properties indicate that the test substance becomes bioavailable following the oral route. This assumption is neither confirmed nor rebutted by the results of an acute toxicity study and a 14-day range finding study conducted with the test substance, as no mortality, effects on body weight, gross pathology and haematology or clinical signs have been reported after acute or repeated oral administration to rats.

 

Due to the melting point of the substance above 70 °C, no availability as a vapour under standard environmental conditions is expected. Still the vapour pressure was determined and is very low. It is 3.7E-4 Pa at 20 °C. As the substance is a powder formation and inhalation of dusts might occur. Generally particles with an aerodynamic diameter below 100 μm have the potential to be inspired, below 50 μm may reach the thoracic region and those below 15 μm can pass into the alveolar region of the respiratory tract. The test substance consists of only ca. 40 % particles smaller or equal to 100 μm (ca. 14 % smaller than 15 μm and ca. 25 % below 50 μm). As demonstrated by the distribution of the particle size the inhalable amount of the test substance is low and less than 15 % of the substance’s particles might possess the ability to reach the alveolar region. Deposited substance can potentially passage through aqueous pores or be carried across membranes with the bulk passage of water, while passive diffusion is less likely due to the low log Pow determined for the substance.

 

As a powder, the substance is not readily taken up by the skin. However, once moistened on the skin surface, absorption is possible, due to the high water solubility determined for the test substance. The molecular weight (194 g/mol) of the substance neither favours nor excludes dermal uptake. Considering the low log Pow between -3.2 and -2.9 of the test substance, the substance is likely to be too lipophobic to cross the stratum corneum, resulting in low dermal absorption.

 

Distribution

As mentioned above, the physicochemical properties of the test substance favour systemic absorption following oral, inhalative and dermal uptake to a certain extent.

Direct transport through aqueous pores is likely to be an entry route to the systemic circulation. After being absorbed into the body, the substance is most likely not distributed into the interior part of cells due to the hydrophilic properties (log Pow between -3.2 and -2.9) and in turn the extracellular concentration is expected to be higher than intracellular concentration.

The test substance does not have a bioaccumulative potential. The log Pow of the test substance indicates no bioaccumulation potential, as it is well below 3. 

 

Metabolism

The genotoxicity studies with the test substance indicate no remarkable differences in regard to genotoxicity and cytotoxicity in the presence or absence of metabolic activation systems. Thus, no metabolic activation is expected. Generally it is likely that common protein interaction such as cytochrome P450 oxidases interaction during Phase I metabolism introduce a reactive or polar group in the substance. The resulting compounds might be further processed into polar compounds during the metabolism in Phase II.

 

Excretion

In general, urinary excretion in favored by low molecular weight (below 300 g/mol in the rat) and good water solubility. Therefore, the test substance is expected to be excreted mostly via urine.