2,6,10-Trimethyldodecane (Farnesane)

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study is conducted according to well established method, but not a GLP guideline study.

Objective of study:

absorption

Qualifier:

no guideline followed

Principles of method if other than guideline:

In vitro absorption across everted gut sac measured as estimation of absorption from the small intestine via the oral route.

GLP compliance:

no

Radiolabelling:

no

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

Intestinal gut sacs were harvested from rats.
Animal: Male Han Wistar rats. Age: approx. 8-12 weeks old obtained from: Charles River, Research Models and Services, Margate, UK.

Route of administration:

other: in vitro test

Vehicle:

other: Fed State Simulated Intestinal Fluid

Details on absorption:

There was no detectable rat small intestinal absorption of Farnesane using the everted rat intestinal sacs. The limit of detection by GC-FID was estimated to be 0.01mM.

The results from the everted rat intestinal sacs incubations with the control mix of alkanes show good absorption of decane with concentrations in the serosal fluid calculated at 0.79mM from Rat 1 intestinal sacs and 0.47mM from Rat 2 intestinal sacs. These concentrations are approximately 20% and 12% respectively of the original incubation conditions of 3.85mM.

Decreased absorption was detected with the increased carbon chain length of the alkanes in the control mix with concentrations of dodecane in the serosal fluid calculated at 0.24mM and 0.14mM (8% and 5% respectively of the original incubation concentration of 3.01mM). Tetradecane concentrations in the serosal fluid were minimal at 0.06mM and 0.03mM (2% and 1% respectively of the original incubation concentration of 2.67mM).
No absorption of the hexadecane and octadecane into the serosal fluid could be detected.

These results are consistent with previous studies performed in this laboratory which have shown an inverse correlation between carbon chain length and the rat small intestinal absorption potential using everted rat intestinal sacs.

Calculated concentration of Farnesane in serosal fluid and external media

Sample	Calculated concentration of Farnesane in serosal fluid and external media (mM)	Mean (mM)	±SD
Serosal fluid 1 Rat 1	0 (0%)
Serosal fluid 2 Rat 1	0 (0%)
Serosal fluid 3 Rat 1	0 (0%)	-	-
Serosal fluid 1 Rat 2	0 (0%)
Serosal fluid 2 Rat 2	0 (0%)
Serosal fluid 3 Rat 2	0 (0%)	-	-
External fluid 1 Rat 1	5.22
External fluid 2 Rat 1	5.23
External fluid 3 Rat 1	5.27	5.24	0.02
External fluid 1 Rat 2	5.14
External fluid 2 Rat 2	5.75
External fluid 3 Rat 2	5.68	5.52	0.34

Conclusions:

Interpretation of results: no bioaccumulation potential based on study results
No gut sac absorption

Executive summary:

The aim of this study was to determine the rat, small intestinal absorption potential of Farnesane and using everted rat intestinal sacs.

 

The results of this study have shown that there was no detectable rat small intestinal absorption of Farnesane using the everted rat intestinal sacs. The limit of detection by GC-FID in FeSSIF media was estimated to be 0.01mM.

 

The results from the everted rat intestinal sacs incubations with the control mix of alkanes show good absorption of decane with concentrations in the serosal fluid calculated at 0.79mM from Rat 1 intestinal sacs and 0.47mM from Rat 2 intestinal sacs. These concentrations are approximately 20% and 12% respectively of the original incubation conditions of 3.85mM.

 

There was diminishing absorption detected with increased carbon chain length of the alkanes in the control mix with concentrations of dodecane in the serosal fluid calculated at 0.24mM and 0.14mM (8% and 5% respectively of the original incubation concentration of 3.01mM). Tetradecane concentrations in the serosal fluid were minimal at 0.06mM and 0.03mM (2% and 1% respectively of the original incubation concentration of 2.67mM). No absorption of the hexadecane and octadecane into the serosal fluid could be detected.

 

Reference - “The use of everted rat small intestinal sacsin-vitroto estimate relative absorption potential of a series of alpha olefins” M. Penman, R. H. Powrie and C. R. Elcombe, Society of Toxicology 2014 Meeting, poster presentation #1593

Description of key information

Farnesane is essentially insoluble in water (0.25μg/L), not expected to hydrolyse in water, has a Log K_ow of 7.5 and is of low volatility (89.3 Pa @ 20°C). One gut sac absorption study demonstrated no bioaccumulation potential based on study results and no gut sac absorption for farnesane.

Additional data available on other alkanes of similar carbon chain length are informative on the possible toxicokinetic properties. See discussion for further details.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

In a study conducted to determine the rat, small intestinal absorption potential of Farnesane using everted rat intestinal sacs, there was no detectable rat small intestinal absorption of Farnesane using the everted rat intestinal sacs. The limit of detection by GC-FID in FeSSIF media was estimated to be 0.01mM (CXR Biosciences, 2014).

 

The results from the everted rat intestinal sacs incubations with the control mix of alkanes showed good absorption of decane with concentrations in the serosal fluid calculated at 0.79mM from Rat 1 intestinal sacs and 0.47mM from Rat 2 intestinal sacs. These concentrations are approximately 20% and 12% respectively of the original incubation conditions of 3.85mM.

 

There was diminishing absorption detected with increased carbon chain length of the alkanes in the control mix with concentrations of dodecane in the serosal fluid calculated at 0.24mM and 0.14mM (8% and 5% respectively of the original incubation concentration of 3.01mM). Tetradecane concentrations in the serosal fluid were minimal at 0.06mM and 0.03mM (2% and 1% respectively of the original incubation concentration of 2.67mM). No absorption of the hexadecane and octadecane into the serosal fluid could be detected. The study demonstrated no bioaccumulation potential based on study results and no gut sac absorption.

Additionally, data available on other alkanes of similar carbon chain length have been used to inform on possible toxicokinetic properties.

Absorption: The low volatility of farnesane indicates that inhalation exposure to vapour is unlikely to occur. Farnesane has a high Log Kow, which suggests that uptake may occur following oral, dermal or inhalation (of aerosol) exposure. The potential for partial uptake orally is supported by experimental studies with C14, C16, C18 alkanes (Le Bon et al 1988, Tulliez et al 1977, Albro 1970,). Data indicate that the small intestine is the major site of absorption but that extensive faecal excretion (66%) of unchanged hydrocarbon occurs.

Dermal studies (Babu et al 2004, Riviere et al 1999, Singh et al 2002) demonstrate uptake of C12 and C14 alkanes, but show that dermal flux of hexadecane (C16) is low in human and pig skin ( 7.02 – 8.8 nmol/cm²/hr x 10E^-3). A review by Kezic et al 2010 indicates that the uptake of tetradecane (C14) and pentadecane (C15) is less than for shorter chain length alkanes ( 0.000140 mg/cm²/hr for C14 and 0.000048 mg/cm²/hr for C16, compared to 0.000410 mg/cm²/hr for C12 and 0.001170 mg/cm²/hr for C10 – based on DERMWINQSAR estimates) .

Distribution: Experimental studies with C16, C18, C19 alkanes (Le Bon et al 1988, Tulliez et al 1977, Anand et al 2007) report that following oral exposure alkanes appear in blood, lymph, adipose tissue and liver. Following dermal exposure it has been reported (Babu et al 2004) that tetradecane (C14) accumulates in the stratum corneum, causing dermal irritation rather than being absorbed systemically.

Metabolism: Evidence of metabolism of absorbed C14, C16, C18, C19 alkanes has been reported both in-vivo and in-vitro (Le Bon et al 1988, Tulliez et al 1977, Anand et al 2007). Metabolism appears to be via Phase 1 oxidative processes, mediated by P₄₅₀isoenzymes (ASTDR 1999). Metabolites reported include alcohols and fatty acids (Le Bon et al 1988, Tulliez et al 1977). An in-vitro study with isolated rat liver microsomes indicated that there was minimal metabolism with tetradecane (C14)

Elimination and Excretion: Following oral administration, extensive faecal excretion of unchanged C19 alkane occurs (Le Bon et al 1988). Absorbed C16 and C18 alkanes are excreted as fatty acids via the urine (Tulliez et al 1977).

 

References

Albro, P.W., Fishbein, L. 1970 Absorption of aliphatic hydrocarbons by rats. Biochimica Biophysica Acta 1219(2): 437-446

Anand Sathanandam, S., Campbell, J.L., Fisher, J. W.2007 In vitro rat hepatic metabolism of n-alkanes: nonane, decane, and tetradecane. International Journal of Toxicology26(4): 325-9.

 

ASTDR 1999. Toxicological profile for Total Petroleum Hydrocarbons (TPH). US Dept of Health and Human Services – Public Health Service

 

Babu R .J., Chatterjee, A., Ahaghotu, E., Singh, M. 2004. Percutaneous absorption and skin irritation upon low-level prolonged dermal exposure to nonane, dodecane and tetradecane in hairless rats. Toxicology and Industrial Health20(6-10): 109-18

 

Kezic S, Kruse J, Jakasa I, 2010. Review of dermal effects and uptake of petroleum hydrocarbons. Concawe Report 5/10. Concawe, Brussels (www.concawe.org)

 

Le Bon, A.M., Cravedi, J.P., Tulliez, J.E.1988, Disposition and metabolism of pristane in rat.Lipids23(5): 424-429.

 

Riviere, J.E.,Brooks, J.D., Monteiro-Riviere , N.A., Budsaba, K., Smith, C.E. 1999. Dermal absorption and distribution of topically dosed jet fuels Jet-A, JP-8, and JP-8(100). Toxicology and Applied Pharmacology160: 60-75

 

Singh Somnath, Zhao Kaidi, Singh Jagdish. 2002 In vitro permeability and binding of hydrocarbons in pig ear and human abdominal skin. Drug and Chemical Toxicology25( 1): 83-92

 

Tulliez J., Peleran J. C. 1977, Demonstration of oxidation of a naphthenic hydrocarbon Dodecylcyclohexane in rats. Febs Letters75(1): 120-122