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INTRODUCTION

Pentadecanol, branched and linear is a lipophilic, white, waxy solid that is practically insoluble in water.

 

 

ABSORPTION

As an aliphatic alcohol, some absorption of pentadecanol, branched and linear is likely to occur following exposure by all common physiological routes (dermal, oral and inhalation) (OECD, 2006). The extent of absorption of aliphatic alcohols varies with chain length. Dermal absorption studies in hairless mice, and comparative in vitro skin permeation data, show that for aliphatic alcohols with chain lengths varying from 8 to 16 carbon atoms, there is an inverse relationship between absorption and chain length. When applied to the skin of hairless mice 2.84% of a dose of radiolabelled n-[1-14C]dodecanol (C12) was absorbed over 24 hours, whereas the absorption of similarly labelled 1-hexadecanol (C16) was about 1% (Iwata et al. 1987). Under these exposure circumstances, dermal absorption of pentadecanol, branched and linear might be predicted to be between 1-2.8%.

 

Lipophilic substances that come into contact with the skin can readily penetrate the lipid-rich stratum corneum by passive diffusion at a rate proportional to their lipid solubility and inversely to their molecular weight (Marzulli et al. 1965).

 

The extent of absorption of aliphatic alcohols from the gastrointestinal tract also depends upon chain length. While short-chain aliphatic alcohols are rapidly and extensively absorbed from the gastrointestinal tract (Aaes-Jorgensen et al. 1959; Bandi et al. 1971a, 1971b), long- chain saturated alcohols (e.g. C18) are said to be poorly absorbed (CIR, 1985).


DISTRIBUTION

Any absorbed pentadecanol, branched and linear potentially could be widely distributed within the body (OECD, 2006). However, its rapid and efficient metabolism and elimination from the body suggests that retention or accumulation of absorbed pentadecanol, branched and linear is unlikely (Bevan, 2001; OECD, 2006). Short-chain aliphatic alcohols readily penetrate the blood-brain barrier, whereas longer chain alcohols (C16-C18) cross this barrier in only trace amounts (Gelman and Gilbertson, 1975).

  

METABOLISM

As a primary alcohol, absorbed pentadecanol, branched and linear will initially be metabolised (oxidised), primarily by alcohol dehydrogenase, to the corresponding aldehyde (pentadecanal). The aldehyde is a transient intermediate that is rapidly converted by further oxidation to the acid (pentadecanoic acid) by aldehyde dehydrogenase. Pentadecanoic acid is then susceptible to degradation via acyl-CoA intermediates by the mitochondrialb-oxidation process. This mechanism removes C2 units in a stepwise process. The rate ofb-oxidation tends to increase with increasing chain length (JECFA, 1999). Mice excretedmore than 90% of the absorbed dose of a slightly shorter-chain alcohol (radiolabelled n-[1-14C]dodecanol) in expired air (evidently as carbon dioxide) following skin application, suggesting that metabolism of pentadecanol, branched and linear would also be extensive (Iwata et al. 1987).

 

An alternative metabolic pathway exists through microsomal or peroxisomal degradation of the carboxylic acid metabolite (pentadecanoic acid) viaw- orw-1 oxidation followed by ß-oxidation (Verhoeven et al. 1998). [This pathway provides an efficient route for the degradation of branched-chain alcohols.]

 

The acids formed from the longer-chained aliphatic alcohols can also enter lipid biosynthesis and may be incorporated in phospholipids and neutral lipids (Bandi et al. 1971a, 1971b; Mukherjee et al. 1980).

 

The hydroxyl function of the parent pentadecanol, branched and linear and the carboxy function of the pentadecanoic acid metabolite may also undergo conjugation reactions to form sulphates and/or glucuronides (Kamil et al. 1953; McIsaac and Williams, 1958). For linear aliphatic alcohols, this pathway generally accounts for less than 10% of the metabolism (Kamil et al. 1953; McIsaac and Williams, 1958).

 

EXCRETION

No data were found for pentadecanol, branched and linear itself. However, when a slightly shorter (C12) analogue (1-dodecanol, radiolabelled with14C on the 1-carbon atom) was applied to the skin of hairless mice, the small amount absorbed (2.84%) was rapidly and extensively eliminated (more than 90% in expired air and a total of 3.5% in the faeces and urine) and only 4.6% of the absorbed dosepentadecanol, branched and linear

Following oral administration of the C16 and C18 analogues (1-hexadecanol and 1-octadecanol) to rats, 20 and 50%, respectively, of the dose was found as unchanged alcohol in the faeces (McIsaac and Williams, 1958; Miyazaki, 1955). Therefore, it seems likely that about 20% of orally administered 1-tetradecanol might be excreted unchanged in the faeces in this species.

 

The glucuronic acid conjugates formed during the metabolism of most aliphatic alcohols are excreted in the urine (Wasti, 1978; Williams, 1959).For 1-decanol (C10) and 1-octadecanol (C18), 3.5% and 7.6% of an oral dose, respectively, was excreted by rabbits in urine as glucuronide (Kamil et al. 1953). A similar result could be predicted for 1-pentadecanol.

 

Although lipophilic alcohols have the physiochemical potential to accumulate in breast milk, rapid metabolism to the corresponding carboxylic acid followed by further degradation suggests that breast milk can only be, at most, a minor route of elimination from the body (OECD, 2006).

 

 

REFERENCES

Aaes-Jorgensen E, Privett OS and Holman RT (1959). Essential fatty acid activities of hydrocarbons and alcohols analogous to linoleate and linolenate. Journal of Nutrition 67, 413-421 (cited in Gelman and Gilbertson, 1975).

 

Bandi ZL, Mangold HK, Holmer G and Aaes-Jorgensen E (1971a). The alkyl and alk-1-enyl glycerols in the liver of rats fed long chain alcohols or alkyl glycerols. FEBS Letters 12, 217-220.

 

Bandi ZL, Aaes-Jorgensen E and Mangold HK (1971b). Metabolism of unusual lipids in the rat. 1. Formation of unsaturated alkyl and alk-1-enyl chains from orally administered alcohols. Biochimica et Biophysica Acta 239, 357-367.

 

Bevan C (2001). Monohydric Alcohols - C7 to C18, aromatic and other alcohols. Patty’s Toxicology. Eds E Bingham, B Cohrssen and CH Powell. 5th Edition, Vol. 6, J. Wiley and Sons, New York (cited in OECD, 2006).

 

Casarett and Doull (1991). Toxicology. The basic science of poisons. Eds MO Amdur, J Doull and CD Klassen. 4thEdition, Pergamon Press, New York.

 

CIR (1985). Final report on the safety assessment of stearyl alcohol, oleyl alcohol and octyl dodecanol. Journal of the American College of Toxicology 4, 1-29.

 

CIR (1988). Final report on the safety assessment of ceteayl alcohol, cetyl alcohol, isostearyl alcohol, myristyl alcohol and behenyl alcohol. Journal of the American College of Toxicology 7, 359-413.

 

FDA (1978). Monograph on stearyl alcohol. US Department of Commerce. NTIS PB-289 664. Food and Drug Administration, Washington DC.

 

Gelman RA and Gilbertson JA (1975). Permeability of the blood-brain barrier to long-chain alcohols from plasma. Nutrition and Metabolism 18, 169-175.

 

Iwata Y, Moriya Y and Kobayashi T (1987). Percutaneous absorption of aliphatic compounds. Cosmetics and Toiletries 102, 53-68.

 

JECFA (1999). Evaluation of certain food additives and contaminants. 49thReport of the Joint FAO/WHO Expert Committee on Food Additives. WHO Tech Rep Series No 884. WHO, Geneva.

 

Kamil IA, Smith JN and Williams RT (1953). Studies in detoxication 46. The metabolism of aliphatic alcohols. The glucuronic acid conjugation of acyclic aliphatic alcohols. Biochemical Journal 53, 129-136 (cited in McIsaac and Williams, 1958).

 

Marzulli FN, Callahan JF and Brown DW (1965). Chemical structure and skin penetrating capacity of a short series of organic phosphates and phosphoric acid. Journal of Investigative Dermatology 44, 339-344 (cited in Casarett and Doull, 1991).

 

McIsaac WM and Williams RT (1958). The metabolism of spermaceti. WA Journal of Biological Chemistry 2, 42-44.

 

MiyazakiM (1955). Nutritive value of aliphatic alcohols II. The nutritive value and toxicity of saturated alcohols of six to eighteen carbon atoms. Journal of the Agricultural and Chemical Society of Japan 29, 501-505 (cited in FDA 1978).

 

Mukherjee KD, Weber N, Mangold HK et al. (1980). Competing pathways in the formation of alkyl, alk-1-enyl and acyl moieties in the lipids of mammalian tissues. European Journal of Biochemistry 107, 289-294.

 

OECD (2006). Long Chain Alcohols. SIDS Initial Assessment Report for SIAM 22.

 

Verhoeven NM, Wanders RJ, Poll-The BT, Saudubray JM and Jacobs C (1998). The metabolism of phytanic acid and pristanic acid in man. A review.Journal of Inherited and Metabolic Diseases 21, 697-728 (cited in OECD, 2006).

 

Wasti K (1978). A literature review – problem definition studies on selected toxic chemicals. Environmental Protection Research Division, US Army Medical Research and Development Command, Maryland USA (cited in CIR, 1988).

 

Williams RT (1959). Detoxification Mechanisms. 2ndEdition, Chapman and Hall,London.