Hydroxyoctadecanoic acid, monoester with glycerol

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Reason / purpose for cross-reference:

read-across source

Objective of study:

excretion

metabolism

Qualifier:

no guideline available

Principles of method if other than guideline:

in vivo feeding study with analysis of body fats. Predates establishment of OECD guidelines.

GLP compliance:

no

Remarks:

Predates GLP

Specific details on test material used for the study:

Hydrogenated castor oil fatty acids. Listed on TSCA Inventory with CAS 61790-39-4. Test material obtained commercially from Emery Industries, Cincinnati OH, USA. Used without further purification.

Radiolabelling:

no

Species:

rat

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

Few details. Male weanling rats, housed singly, were fed a diet with varying sources of fat.

Route of administration:

oral: feed

Vehicle:

corn oil

Duration and frequency of treatment / exposure:

Test substance was administered in the feed for 8 weeks (59 days).

Dose / conc.:

10 other: % fat

Remarks:

The test fat represented 10% and an added cottonseed oil 2% of the 12% of total fat.

No. of animals per sex per dose / concentration:

5

Control animals:

yes

Positive control reference chemical:

no positive controls

Details on study design:

A basal diet containing 12% of fat was used in all experiments. The test fat represented 10% and fresh cottonseed oil 2 % of the 12 % of fat (see Perkins and Kummerow, 1959, J. Nutrition 68: 101). The diets were kept stored under nitrogen and refrigerated to prevent fat deterioration. Groups of 5 male weanling rats each were kept in single cages, weighed on alternate days, and arbitrarily restricted to the same amount of food intake as those fed corn oil. Animals were maintained on identical amounts (weight) of the diets for 59 days. Samples of the feces were collected and frozen. After the test period the animals were sacrificed, the livers removed, weighed, the carcass frozen until required.

The total carcass fat of the rats was obtained by digestion and extraction of the digested carcass according to the procedure of Johnston et al. (1958, J. Nutrition 65:13). Rat feces samples were pooled within groups, and fatty acids extracted. Aliquots of the fat samples were converted to their corresponding methyl esters prior to gas-liquid chromatographic analysis. Wijs iodine values were determined in duplicate on each fat sample according to the official AOCS method. Acetyl values were determined according to the method of Ogg et al. (1945, Ind. Eng. Chem. Anal., ed., 1: 394).

There were 4 study groups and two control groups. The controls were diets which were supplemented with corn oil or corn oil fatty acids. The fresh corn oil diet supplement was obtained locally and was a light-colored refined corn oil. Corn oil fatty acids were prepared from fresh corn oil by saponification of the oil with potassium hydroxide in 95% ethanol; regeneration of the acids from the soaps by acidification with dilute hydrochloric acid, and extraction with petroleum ether. The extracts were washed several times with water to remove all mineral acid, and dried over anhydrous sodium sulfate. Solvent was removed by distillation with the aid of steam heat; the last traces of solvent were removed under vacuum. The fresh corn oil fatty acids thus prepared were stored under nitrogen in the cold until used.

Ricinoleic acid was prepared from purified triricinolein in a similar manner and was also stored in the cold until required. Triricinolein was prepared by the exhaustive extraction of castor oil with petroleum ether. After 10 extractions of one kilogram of castor oil with one liter portions of petroleum ether, a triricinolein concentrate was obtained which was found to be about 97% pure (% OH = 5.04; theory = 5.47) . This material was used without further purification. Hydrogenated castor oil fatty acids were obtained commercially and were used without further purification. The shortening used in these experiments was also obtained locally and was a hydrogenated animal-vegetable fat shortening.

Gas-liquid chromatographic analysis of fatty acid methyl esters: The gas chromatographic analyses of the fats were carried out using an instrument constructed in the laboratory, and a thermal conductivity detector system. A 4-foot, ¼ inch internal diameter copper column was packed with 60%
60 to 80 mesh Chromasorb which was impregnated with 40% by weight of a succinic anhydride-diethylene glycol polyester as the stationary phase. Columns were stable up to 210°C and provided well­defined separations of saturated and unsaturated compounds in the fatty acid methyl ester series, but were unable to separate the isomeric unsaturated 16 and 18 carbon fatty acid methyl esters. Analyses were usually run at 190 to 205°C with a He pressure of 11 pounds per square inch, which resulted in a flow rate of about 60 ml of gas per minute. A standard mixture was analyzed periodically as a check of column condition. For a typical analysis of fatty acid methyl esters, 1 to 5 µl of the ester were injected into the column with a micro syringe. The analysis required from 30 to 60 minutes to complete. Identification was based on comparison of the retention time of the esters with those of authentic samples. The composition of each mixture analyzed was calculated on the basis of the area under each peak, as found by the triangulation method.

Details on dosing and sampling:

see study design

Statistics:

see study design. Standard deviations for body and organ weights were determined using current acceptable methods.

Preliminary studies:

Additional information on the main study: rats fed fats containing hydroxyl groups gained slightly less weight than those fed shortening or fresh corn oil. Rats fed diets containing 10% of a commercial shortening or fresh corn oil weighed between 190 to 207 gm at the termination of the growth study; those fed hydroxylated fats at the same level weighed from 157 to 199 gm. Statistically significant differences were found in the growth of animals fed ricinoleic acid and hydrogenated castor oil fatty acids when compared with those fed fresh corn oil, whereas those animals fed ricinoleic acid in the form of the triglyceride gained as much weight as those fed fresh corn oil diets. This may be due to reduced absorption of the fatty acids compared to triglycerides. Livers were slightly enlarged, as were the livers of those fed triricinolein. Statistically significant differences in liver enlargements were observed in livers of animals fed ricinoleic acid when compared with those fed fresh corn oil and fresh corn oil acids; but no significant differences were observed in the livers of rats fed either ricinoleic acid or hydrogenated castor oil fatty acids. Hepatomegaly may be due to an attempt to compensate or use a foreign fat to produce a more "normal" type of glyceride or fatty acid.

Type:

absorption

Results:

Dietary hydrogenated castor oil fatty acids were absorbed and found in the carcass fat.

Type:

excretion

Results:

Dietary hydrogenated fatty acids were absorbed and excreted in feces.

Details on absorption:

The degree of utilization of the ingested fats, as measured by the ratio of weight gain of animals fed the test fat to those fed fresh corn oil, was 83.5 and 85.8% for ricinoleic acid and hydrogenated castor oil fatty acids, respectively, and that of triricinolein was 97.0% of that of corn oil or a commercial shortening (100%). The gastrointestinal absorption of the test fats was not examined, and may explain why the utilization of the ricinoleates was slightly lower than that of corn oil.

The fatty acid composition of the carcass fat of rats fed fresh corn oil and the corresponding fatty acids showed a high linoleic, oleic and palmitic acid content. A small amount of hexadecenoic acid was also deposited. No significant amounts of hydroxy acids were noted in the carcass fats of animals fed diets containing fresh corn oil and fresh corn oil fatty acids. In these rats fed corn oil, the composition of feces fat exhibited a marked increase in stearic acid and a decrease in linoleic acid content. Animals fed fresh corn oil fatty acids had very similar carcass and feces fat composition, except for stearic acid which increased from 2.4 to 8.3% and myristic acid, which decreased from 2.5 to less than 1%.

Ingestion of hydroxy acids both in the form of their triglycerides and as the free fatty acids caused marked changes in both carcass and fecal fat composition when compared with the effects of corn oil and shortening. Animals fed hydroxylated material had approximately the same carcass and feces fat composition: levels of oleic acid were very high (41 to 45%) ,and levels of linoleic acid were low (8.6 to 10.0%). Approximately double the amount of linoleic acid was excreted as found in the carcass fats, and a 5-fold amount of stearic acid was excreted compared with deposited. The level of palmitic acid deposited and excreted remained almost equal.

The results obtained in the present study indicate that the rat, when fed hydroxy acids as a metabolizable fat source, forms a body fat profile similar to that of a more usual fat source (corn oil). The presence of considerable amounts of hexadecenoic acid in the carcass fats of animals fed hydroxy acids and its near absence in the feces fats remains to be explained. It appears that this acid is preferentially deposited in the carcass fats of animals fed hydroxy acid-containing diets. The presence of this acid in the fats of animals fed fresh corn oil and fresh corn oil fatty acids was substantially lower (60 to 75%).

Details on excretion:

In rats fed corn oil or corn oil, the composition of feces fat exhibited a marked increase in stearic acid and a decrease in linoleic acid content. Animals fed fresh corn oil fatty acids had very similar carcass and feces fat composition, except for stearic acid which increased from 2.4 to 8.3% and myristic acid, which decreased from 2.5 to less than 1%. Excretion of a higher melting point substance, such as stearic acid, could explain a preferred retention of fats with a low melting point, near that of the animals' body temperature.

Animals fed hydroxylated material had approximately the same carcass and feces fat composition: levels of oleic acid were very high (41 to 45%), and levels of linoleic acid were low (8.6 to 10.0%). Approximately double the amount of linoleic acid was excreted as found in the carcass fats, and a 5-fold amount of stearic acid was excreted compared with deposited. The level of palmitic acid deposited and excreted remained almost equal.

The presence of considerable amounts of hexadecenoic acid in the carcass fats of animals fed hydroxy acids and its near absence in the feces fats remains to be explained.

Comparison of Dietary Supplement Fatty Acid Composition

Fatty acid composition	Fresh corn oil	Fatty acids from fresh corn oil	Triricinolein	Ricinoleic acid	Hydrogenated castor oil fatty acids	Commercial shortening
	%	%	%	%	%	%
Linoleic	54.4	54.4	̶	̶	̶	10.1
Oleic	28.8	28.8	̶	̶	̶	39.9
Stearic	2.3	2.3	3.0	3.0	10.9	17.5
Hexadecenoic	̶	̶	̶	̶	̶	3.5
Palmitic	13.0	13.0	̶	̶	5.1	23.7
Myristic	0.2	0.2	̶	̶	̶	3.5
Lauric	0.4	0.4	̶	̶	̶	1.1
Hydroxy acids	̶	̶	97.0	97.0	84.3	̶
Iodine value	126.0	124.0	81.6	85.2	0.4	49.5

 

The Influence of Dietary Fat on the Carcass and Feces Fatty Acid Composition of the Rat

Fatty acid composition

Fresh corn oil

Fatty acids from fresh corn oil

Triricinolein

Ricinoleic acid

Hydrogenated castor oil fatty acids

Commercial shortening

Carcass

Feces

Carcass

Feces

Carcass

Feces

Carcass

Feces

Carcass

Feces

Carcass

Feces

%

%

%

%

%

%

%

%

%

%

%

%

Linolenic

0.2± 0.5

̶

0.8 0.8

̶

̶

̶

0.1 ± 0.2

̶

̶

̶

0.4 ± 0.5

̶

Linoleic

36.1 ± 2.3

17.9

32.9 ± 3.8

40.4

10.0 ± 1.1

17.7

8.6 ± 1.1

26.9

9.3 ± 1.1

17.2

9.9 ± 1.0

3.6

Oleic

31.9 ± 1.3

34.3

33.2 ± 1.2

38.4

45.3 ± 2.0

27.6

41.8 ± 1.4

25.7

42.3 ± 4.0

24.6

47.1 ± 2.1

27.3

Stearic

2.9 ± 0.8

17.8

2.4 ± 0.7

8.3

3.5 ± 0.6

16.2

3.9 ± 0.5

11.7

4.4 ± 0.8

25.1

4.0 ± 0.6

21.9

Hexadecenoic

5.1 ± 0.0

8.8

6.0 ± 0.6

̶

11.7 ± 1.9

̶

14.1 ± 1.5

3.2

10.4± ± 0.5

̶

8.9 ± 1.4

3.6

continued:

Fatty acid composition	Fresh corn oil		Fatty acids from fresh corn oil		Triricinolein		Ricinoleic acid		Hydrogenated castor oil fatty acids		Commercial shortening
	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces
	%	%	%	%	%	%	%	%	%	%	%	%
Palmitic	21.4 ± 2.4	25.6	22.4 ± 1.0	11.6	26.6 ± 0.1	27.9	28.8 ± 2.4	24.1	30.2 ± 3.2	30.4	24.9 ± 3.6	39.3
Myristic	1.6 ± 0.7	10.2	2.5 ± 0.5	0.6	2.6 ± 0.1	5.1	2.6 ± 0.3	3.6	2.4 ± 0.1	1.6	3.1 ± 0.0	3.8
Tetradecenoic	0.1 ± 0.0	̶	0.6 ± 0.2	̶	0.6 ± 0.2	̶	0.3 ± 0.2	̶	0.1 ± 0.1	̶	0.2 ± 0.1	̶
Lauric	0.3 ± 0.5	2.8	0.6 ± 0.1	0.6	0.4 ± 0.2	5.7	0.4 ± 0.1	4.9	0.4 ± 0.1	1.0	0.7 ± 0.4	0.5
Hydroxy acids	1.5 ± 1.0	2.5	̶	2.5	7.5 ± 1.0	̶	5.5 ± 0.7	3.5	6.1 ± 3.6	3.7	2.2 ± 0.5	3.8
	%	%	%	%	%	%	%	%	%	%	%	%
Palmitic	21.4 ± 2.4	25.6	22.4 ± 1.0	11.6	26.6 ± 0.1	27.9	28.8 ± 2.4	24.1	30.2 ± 3.2	30.4	24.9 ± 3.6	39.3
Myristic	1.6 ± 0.7	10.2	2.5 ± 0.5	0.6	2.6 ± 0.1	5.1	2.6 ± 0.3	3.6	2.4 ± 0.1	1.6	3.1 ± 0.0	3.8
Tetradecenoic	0.1 ± 0.0	̶	0.6 ± 0.2	̶	0.6 ± 0.2	̶	0.3 ± 0.2	̶	0.1 ± 0.1	̶	0.2 ± 0.1	̶
Lauric	0.3 ± 0.5	2.8	0.6 ± 0.1	0.6	0.4 ± 0.2	5.7	0.4 ± 0.1	4.9	0.4 ± 0.1	1.0	0.7 ± 0.4	0.5
Hydroxy acids	1.5 ± 1.0	2.5	̶	2.5	7.5 ± 1.0	̶	5.5 ± 0.7	3.5	6.1 ± 3.6	3.7	2.2 ± 0.5	3.8
Iodine value

continued:

Fatty acid composition	Fresh corn oil		Fatty acids from fresh corn oil		Triricinolein		Ricinoleic acid		Hydrogenated castor oil fatty acids		Commercial shortening
	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces	Carcass	Feces
	%	%	%	%	%	%	%	%	%	%	%	%
Iodine value	99.7 ± 3.7	103.0	99.7 ± 1.4	103.7	71.5 ± 4.0	65.5	68.5 ± 2.9	85.7	66.4 ± 1.3	83.6	69.9 ± 1.4	62.2

Conclusions:

The toxicokinetics of hydrogenated castor oil and other related compounds (relevant for GMHS) was studied in an in vivo absorption and fat deposition study. In a study in which rats were given diets having different types of fat (corn oil, corn oil fatty acids, triricinolein, ricinoleic acid, hydrogenated castor oil fatty acids and a commercial shortening), differences were seen in terminal body weight, liver weight, carcass fat content and fecal fat content after 8 weeks. Dietary hydroxy acids are absorbed and utilized, and, within this 8 week period, influence the character of the normal mixed fatty acid composition of the carcass fat. Both saturated and unsaturated hydroxy fatty acids are converted to monoenoic acids in the rat. A larger amount of oleic acid and hexadecenoic acid seemed to be deposited and a preferential excretion of stearic and linoleic acids seemed to occur in rats fed a source of hydroxy fatty acids, in comparison with those fed a source of linoleic acid. Hydroxy fatty acids were also observed in the carcass and fecal fat of animals fed only corn oil, corn oil fatty acids and commercial shortening, suggesting the possibility that hydroxy fatty acids may be formed de novo.

Description of key information

Absorption of orally administered hydrogenated castor oil (analogue of GMHS) was documented

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

100

Absorption rate - inhalation (%):

100

Additional information

Mono-, di- and triglycerides of castor oil were investigated for pharmacokinetic parameters of absorption, distribution, metabolism and excretion. Orally administered triglyceride is acted upon by gastrointestinal lipase, forming mono- and diglycerides absorbed into intestinal cells and handled in a similar manner to fats found in the normal diet. These lipids are catabolised by the β- oxidation pathway, forming shorter fatty acids by 2 carbons. No bioaccumulation is anticipated, due to the known metabolic breakdown pathways. Castor oil itself is listed on REACH Annex IV (now Annex V as a vegetable oil), is a medicinal product used by human for generations; and it and related compounds are approved by EFSA and FDA as indirect food additives. DHI, as consultants to ECHA, reviewed the data on castor oil as listed on Annex IV, and concluded that the existing data are sufficient to allow the conclusion that the substance is appropriate for Annex IV/V listing, without hazard for harmful effects for human health or the environment.