Grapefruit, ext.

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The results were obtained for the known constituents of Grapefruit Oil, combining empirical and calculated results (estimated by the QSAR Kowwin v 1.67). The constituents of Grapefruit oil fall within the applicability domain of the model. The results provided are adequate for the purpose of Classification and Labelling

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

The partition coefficient of a NCS has little meaning. The range of Log Kow was based on empirical results for limonene and for the constituents the results were predicted based on structural molecular fragments by the KOWWIN program of EPIWIN.

Calculated and measured data on the constituents are obtained from Kowwin v1.67. Figure 1 (attached as a picture) shows that most measured values are lower than the estimated values. It is also clear from the figure that for many constituents, measured log Kow values vary. Sometimes this variation is more than one log unit, especially for the more hydrophobic constituents with a log Kow > 4. It is generally recognized that the log Kow determination of more hydrophobic substances is easily prone to experimental flaws and that for this group it is important to use adequate methods designed to determine higher log Kow values.

This is considered valid because of the variation of measured log Kow values for the constituents, the unknown method of determination and because the calculated log Kow are generally more conservative (higher) than the measured log Kow.

GLP compliance:

no

Type of method:

other: calculation by estimation and empirical for major constituent

Partition coefficient type:

octanol-water

Key result

Type:

log Pow

Partition coefficient:

>= 2.78 - <= 6.3

Temp.:

25 °C

pH:

7

Details on results:

No data

Substance	CAS	Fraction	Estimated log Kow
D-limonene	5989-27-5	0.88	4.38 (measured, Griffin et al 1999)
Citral	5392-40-5	0.005	3.45
Myrcine B	123-35-3	0.02	4.88
Linalool	78-70-6	0.005	3.38
alpha-pinene	7785-70-8	0.005	4.27
Beta-caryophyllene	87-44-5	0.01	6.30
Citronellal	106-23-0	0.005	4.75
Decanal	112-31-2	0.015	3.76
Nootkatone	4674-50-4	0.01	4.88
Octanal	124-13-0	0.01	2.78
Sabinene	3387-41-5	0.005	4.69

Conclusions:

The log Kow range of the known constituents of grapefruit oil is 2.78 - 6.3. The percentage of constituents with log Kow > 4 is 93.5%.

Executive summary:

Log Kow was estimated for the constituents of Grapefruit Oil using the program KOWWIN of EPIWIN. The validity of the approach was checked by comparison of measured and predicted values for related substances. Only for the main constituent limonene the empirical log Kow was used.

The log Kow range for known grapefruit oil constituents was found to be 2.78 - 6.3. The percentage of constituents with log Kow > 4 is 93.5%.

Description of key information

The log Kow of the constituents of Grapefruit Oil is above 4.0 for more than 90% of the composition. With log Kow 4.83 (predicted) or 4.38 (measured), limonene represents the group with a high log Kow.  

Key value for chemical safety assessment

Log Kow (Log Pow):

4.38

Additional information

The predicted log Kow of the constituents of Grapefruit Oil (typical composition) ranges from 2.78 - 6.3. Log Kow is above 4.0 for 93.5% of the typical constituent composition, whereas the lowest (2.78) and highest (6.3) values were for constituents comprising 1% of the NCS each. For limonene the log Kow was 4.83 (predicted) or 4.38 (measured, Griffin et al, 1999).