Sophorolipids: fermentation products of glucose and fatty acids, C18 (unsaturated), glycerol esters with yeast Candida Bombicola, partially hydrolysed

Endpoint summary

Description of key information

There are no studies available in which the toxicokinetic behaviour of Sophorolipids, partially hydrolysed, has been investigated.

Therefore, in accordance with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2014), assessment of the toxicokinetic behaviour of Sophorolipids is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to Guidance on information requirements and chemical safety assessment.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

There are no studies available in which the toxicokinetic behaviour of Sophorolipids, partially hydrolysed, has been investigated.

Therefore, in accordance with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2014), assessment of the toxicokinetic behaviour of Sophorolipids is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to Guidance on information requirements and chemical safety assessment.

Parameter	Value
Molecular weight	> 600 g/mol. Recently used batch for testing: 637 g/mol (according to the manufacturer)
Melting Point	150 °C, decomposition
Boiling Point	Not applicable; decomposition
Density D^204	1.1081
Vapour pressure	1.1E-17 Pa (QSAR)
Partition coefficient n-octanol / water (logKow)	2.4
Water solubility	147 g/L (filtrated)
CMC	0.2 – 0.4 g/L
Solubility in organic solvents	3 – 5 g/L
Surface tension	37.3 nM/m
Particle size	Handled only in solution

 

Chapter R.7c: Endpoint specific guidance (ECHA, 2008)

The components of this UVCB substance consist of two sugar units (sophorose) bearing a fatty acid chain (which is derived from C18 unsaturated fatty acids with different degree of unsaturation), both as lactone form and as acidic form. Some of the free hydroxyl-groups of the sugar units are acetylated.

Sophorolipids are solid at room temperature and have a molecular weight of ca. 637 g/mol according to the information given for a recent batch. Besides, the test item is handled only in solutions.

The measured water solubility of the filtrated test item was 147 g/L, while the critical micelle concentration (CMC) was 0.2 to 0.4 g/L. Solubility in organic solvents was 3 – 5 g/L.

The logKow has been calculated to be 2.4. This calculation has been derived from the measurements of CMC and solubility in octanol as a worst case LogKow value.

The substance possesses surface activity. The determined value was 37.3 nM/m.

 The vapour pressure is calculated to be 1.1E-17 Pa at 25 °C.

Oral absorption

In general, molecular weights below 500 are favourable for oral absorption while molecular weights above 1000 do not favour absorption (ECHA, 2014). As the average molecular weight of Sophorolipids is >600 g/mol, absorption of the molecule in the gastrointestinal tract according to molecular weight is thought to be reduced but may still occur to a relevant extent. Also, the logKow of 2.4 is in a range suggestive of absorption from the gastro-intestinal tract subsequent to oral ingestion (log Kow between -1 and 4).

Overall, a systemic bioavailability of Sophorolipids and/or the respective cleavage products in humans is considered likely after oral uptake of the substance. For chemical safety assessment an oral absorption rate of 50 % is assumed as a worst-case default value in the absence of other data.

Dermal absorption

The smaller the molecule, the more easily it may be taken up. In general, a molecular weight below 100 favours dermal absorption, above 500 the molecule may be too large (ECHA, 2014). The molecular weight of Sophorolipids is >600g/mol is thus not favourable for dermal absorption. Besides, logKow values between 1 and 4 favour dermal absorption (values between 2 and 3 are optimal) particularly if water solubility is high. The logKow of 2.4 as a worst-case assumption may in this case favour dermal absorption, while the molecular weight of >600 g/mol, as stated above, may not.

If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration (ECHA, 2014). As Sophorolipids are not skin irritating in humans, enhanced penetration of the substance due to local skin damage is not expected.

For chemical safety assessment a dermal absorption rate of 50 % is assumed as a worst-case default value in the absence of other data.

Inhalation absorption

For chemical safety assessment an inhalation absorption rate of 100 % is assumed as a worst-case default value in the absence of other data.

Distribution, Metabolism and Excretion

Distribution within the body through the circulatory system depends on the molecular weight, the lipophilic character and water solubility of a substance. In general, the smaller the molecule, the wider is the distribution. If the molecule is lipophilic, it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues (ECHA, 2014). Besides, the test substance is most likely rapidly degraded after uptake and thus, the characteristics of the parent compound do not apply. The sugar units and the fatty acids resulting from breakdown are thought to be absorbed and metabolized rather rapidly.After[JF1] oral ingestion, esters of short-chain (C2-8) alcohols and fatty acids undergo stepwise chemical changes in the gastro-intestinal fluids as a result of hydrolysis. This firstly leads to the acidic form of Sophorolipids. Therefore, the lactone form of the Sophorolipid will be hydrolysed and will result in the acidic form. The test substance, once the acid form is prevalent after oral ingestion, is likely to undergo further breakdown in the GI tract. According to the publication by Saghir et al. (1997), fatty acid ethyl esters are very rapidly and extensively hydrolysed in the GI tract at the level of the duodenum and in the blood. Guidance R.7c states that when the physico-chemical characteristics of the further cleavage products (e.g. physical form, water solubility, molecular weight, log Pow, vapour pressure, etc.) are likely to be different from those of the parent substance before absorption into the blood takes place, the predictions based upon the physico-chemical characteristics of the parent substance do no longer apply (ECHA, 2014). However, also for the cleavage products, it is anticipated that they are absorbed in the gastro-intestinal tract. The highly lipophilic fatty acid is absorbed by micellar solubilisation (Ramirez et al., 2001), whereas the sugar units are readily dissolved into the gastrointestinal fluids and absorbed from the gastrointestinal tract. The metabolic fate of the fatty acids derived from hydrolysis then depends on the organ or tissue into which it is incorporated. Besides, the further metabolic fate of the fatty acids is considered irrelevant in terms of toxicokinetic assessment as they do structurally not differ from those derived from nutritional fat.

For Sophorolipids, the main route of excretion is expected to be by expired air as CO₂after metabolic degradation. The second route of excretion is expected to be by biliary excretion with the faeces. For the cleavage products, the main routes are renal excretion via the urine and exhalation as CO₂.

Based on the available data no additional conclusions can be drawn on the distribution, metabolism and excretion of Sophorolipids.

Due to the lack of experimental data, 100 % absorption by inhalation and 50 % absorption via the oral and dermal route is assumed as worst case default for chemical safety assessment.