Disodium L-cystinate

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

20 May 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

Please refer to QPRF/QMRF documentation for detailed information on model suitability.

Data source

Reference

Reference 1

Reference Type:

other: QSAR

Title:

KOWWIN v1.68 (September 2010) - octanolwater partition coefficients

Author:

US EPA

Year:

2017

Bibliographic source:

EpiSuite v4.1, United States Environmental Protection Agency

Report date:

2017

Reference 2

Reference Type:

publication

Title:

Atom/fragment contribution method for estimating octanol-water partition coefficients

Author:

Meylan WM, Howard PH

Year:

1995

Bibliographic source:

J. Pharm. Sci. 84: 83-92, 1995

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals

Version / remarks:

May 2008

Principles of method if other than guideline:

QSAR prediction using KOWWIN v1.68 of EpiSuite v4.1. QSAR calculation is based on the fragment constant methodology.

GLP compliance:

no

Type of method:

other: QSAR calculation

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

Disodium L-cystinate

EC Number:

265-025-3

EC Name:

Disodium L-cystinate

Cas Number:

64704-23-0

Molecular formula:

C6H10N2Na2O4S2.H2O

IUPAC Name:

disodium (2R)-2-amino-3-{[(2R)-2-amino-2-carboxyethyl]disulfanyl}propanoate

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

SMILES : O([Na])C(=O)C(N)CSSCC(N)C(=O)O([Na])

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

ca. -7.57

Temp.:

20 °C

Remarks on result:

other: pH not available in QSAR prediction

Details on results:

see QPRF/QMRF

Applicant's summary and conclusion

Conclusions:

The estimated log Pow = -7.57 for Disodium L-cystinate is very low and suggests hydrophilic properties associated with only a minor potential for adsorption and bioaccumulation.

Executive summary:

In general, KOWWIN makes log P estimates that are “corrected for ionization”: i.e., KOWWIN estimates apply to compounds that are predominantly in a non-ionized form. However, KOWWIN is also capable to give log P estimates for “ion pair” compounds. Effectively, the estimate for Disodium L-cystinate is an estimate for ionized cystine with additional fragment contributing factors for the sodium counter ion. This approach is considered reasonable. The model result for Disodium L-cystinate with a log Pow value of -7.57 matches the general behaviour for ionic compounds in a polar (water) and nonpolar (octanol) environment and suggests hydrophilic properties associated with a minor potential for adsorption and bioaccumulation. Disodium L-cystinate is inside the applicability domain of the model and the result is considered adequate for a regulatory purpose.