Potassium hexadecyl hydrogen phosphate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1967

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Objective of study:

other: absorption, excretion, metabolism

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

GLP compliance:

not specified

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 300 g
- Fasting period before study: no
- Diet, water: ad libitum a water solution of an acid hydrolysate of casein (2%), sucrose (7.6%), Wesson's salt mixture {0.4%), and water-soluble vitamins, starting the evening before the thoracic duct or the bile duct was cannulated
- Housing: During the lymph and bile collections, the rats were kept in restraining cages of the type described by BOLLMAN and supplied with the diet solution from an inverted bottle.

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
- 0.2 mg [14C]cetyl alcohol and 300 mg [14C]cetyl alcohol. 0.2 mg and 300 mg [14C]cetyl alcohol were administered in 0.5 mL and 0.6 mL corn oil, respectively, by stomach tube . Each dose contained 1-1.5 µCi of 14C-radioactivity.

Duration and frequency of treatment / exposure:

24 or 48 hours

Dose / conc.:

0.7 mg/kg bw (total dose)

Dose / conc.:

1 000 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

2 male rats. 1 rat per dose.

Control animals:

no

Positive control reference chemical:

No

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled : urine, faeces, lymph, bile, serum and various tissues
- Time and frequency of sampling:
- Other: Analytical methods: [I-14C]cetyl alcohol was obtained commercially and purified by thin-layer chromatography.

METABOLITE CHARACTERISATION STUDIES
- Method type(s) for identification: Thin layer chromatography of lipids

Preliminary studies:

No

Type:

absorption

Results:

Approximately 30-40 % of the [14C]-cetylalcohol administered dose are absorbed from the GIT after oral administration.

Details on absorption:

Systemically available.

Details on distribution in tissues:

About 30-40 % of the radioactivity were detected in urine, expired air, residual carcass, lymph and liver -> systemically distributed

Details on excretion:

60 - 70 % in feces

Metabolites identified:

yes

Details on metabolites:

Triglycerides

- Cetyl alcohol was extensively (85%) converted (during lymphatic absorption) to saponifiable material which migrated (after methylation) with the normal fatty acid methyl esters and was presumed to be palmitic acid. The cetyl alcohol that was absorbed in non-saponifiable form was present largely in a complex that migrated ahead of the triglycerides.

Conclusions:

Approximately 30-40% of the administered dose are absorbed from the GIT after oral administration. No radioactivity was detected in urine. Small amount of radioactivity were found in expired air (1-2%). The majority of the radioactivity is recovered in feces and intestine. Cetyl alcohol is most likely present in the animal body and is metabolized into its corresponding fatty acid which is then incorporated into triglycerides.

Executive summary:

In the present study 14C-labeled cetyl alcohol (among other substances and mainly used for comparable measures) was administered by gastric intubation to rats in which the thoracic lymph duct had been cannulated. Radioactivity in the drained lymph and in the expired CO2 was determined periodically, and radioactivity (including radioactive metabolities) in the tissues was determined after 24 or 48 h. 14C-labelled cetyl alcohol was administered at a dose level of 0.7 and 1000 mg/kg bw in corn oil to rat and was found to be systemically available. About 30-40 % of the radioactivity were detected in urine, expired air, residual carcass, lymph and liver. Whereas the remaining 60-70 % were recovered from feces. Cetyl alcohol is most likely present in the animal body and is metabolized into its corresponding fatty acid which is then incorporated into triglycerides.

Reference 2

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987-07-20 until 1987-07-23

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

No OECD guideline available at the time the study was performed. Nevertheless the study is similar (with deviations) to OECD guideline 428, scientifically acceptable with some reporting deficiences

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Version / remarks:

13 April 2004

Deviations:

yes

Remarks:

deviations in absorption period, dose applied lower than 10 µL/cm², only one concentration applied.

GLP compliance:

no

Radiolabelling:

yes

Species:

other: In this in vitro study, skin from naked rats and pigs was used.

Strain:

not specified

Sex:

not specified

Type of coverage:

not specified

Vehicle:

ethanol

Remarks:

30 %

Duration of exposure:

1, 6, 16 hours

Doses:

6 µL/cm² equivalent to 300 µg active substance / cm² (the test substance was formulated to yield a concentration of 5% in ethanol (30%)).

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: skin from naked rats and pigs
- Preparative technique:
Active substance prepared 1-5 µCi/ 5 cm² skin site.
Excision of the skin – the skin was separated from fresh operation material. The coonective and adipose tissue is carefully removed and then the skin is separated into round flaps of ca. 20 cm². Every piece was cleaned under floating water, and thereafter is either used directly for the experiment or stored in aluminium foil at -20°C.
Preparation of the excised skin – the skin specimen were marked with areas of 5 cm². 30 µL of the test substance were applied regularly with micropipette on the marked areas. The skin specimen were clamped into the penetration chambers. The lower part of the prepared skin was in constant contact with physiological salt solution, which was slightly moved by a magnetic stirrer throughout the whole experiment (1, 6, 16 hours).

PRINCIPLES OF ASSAY
- Diffusion cell: yes
- Receptor fluid: 0.9 % (w/v) NaCl (continuously stirred)
- Static system: yes
- Test temperature: 32°C
- Occlusion: not specified
- Other: The measurement of activity was carried out with a Packard liquid scintillation spectometer

Absorption in different matrices:

Most of the radioactivity could be washed off. Minor amounts of radioactivity could be recovered from stratum corneum, epidermis, dermis and receptor fluid. Mean levels of expressed as µg/cm² are presented in a table below in "any othe information on results"

Total recovery:

- Total recovery: naked rat skin or pig skin - 300 µg/cm²
Most of the radioactivity could be washed-off from stratum corneum.

Key result

Dose:

6 µL/cm²

Parameter:

percentage

Absorption:

> 5.2 - < 9 %

Remarks on result:

other: 1 - 16 hours

Remarks:

mean penetration percent in naked rat and pig skin

		Naked rat skin
µg/cm^2in		Contact time
	1h	6h	16h
skin wipe	261.98	235.37	181.14
Horny layer	22.44	37.37	99.25
Remaining skin tissue layers	15.58	23.85	12.44
Chamber liquid	--	3.41	7.17
Total recovery	300	300	300
Systemic available[1]	15.6	27.3	19.61
Systemic available[2](%)	5.2	9.0	6.5
		Pig skin
skin wipe	269.13	262.52	218.19
Horny layer	13.93	13.97	56.02
Remaining skin tissue layers	16.94	20.34	19.96
Chamber liquid	--	3.17	5.83
Total recovery	300	300	300
Systemic available	16.94	23.51	25.79
Systemic available (%)	5.6	7.9	8.6

 

[1]Amount in skin (without horny layer) and receptor fluid

[2]Calculated based on applied active substance (300 µg/cm²)

Conclusions:

The test substance (14C-Amphisol) penetrates into skin. Overall, mean penetration was between 5.2 % and 9.0 %. Most of the radioactivity could be washed-off from stratum corneum.

Executive summary:

The in-vitro percutaneous penetration of the test substance was determined using skin from naked rat or pig (thickness not indicated). The penetration was investigated in a static system. The test substance was formulated to yield a concentration of 5% in ethanol (30%). The formulations were applied at dose levels of 6 µL per cm2 (equivalent to 300 µg per cm²) at a temperature of 32°C. Occlusion conditions not specified. Skin integrity testing if performed was not reported.

The penetration of the test substance was determined over 1, 6, and 16 h. After respective contact duration, the skin was wiped with cotton wool, the horny layer was removed by tape stripping. The total radioactivity was determined in all samples (skin wipe, tape strips, remaining skin, receptor fluid, chamber) collected by means of liquid scintillation counting.

Most of the radioactivity could be washed off. Minor amounts of radioactivity could be recovered from stratum corneum, epidermis, dermis and receptor fluid. Based on the radioactivity found in remaining skin and receptor fluid the amount of the test substance absorbed represented between 5.2 – 9.0 %. This corresponds to 15.6 – 27.3 µg test substance equivalents/cm2. Exposure time and type of skin showed no real influence on penetration rate.

Description of key information

The registered material is a mono-constituent substance consisting of monocetyl phosphate, dicetyl phosphate and cetyl alcohol. Dermal penetration is considered to be 9 % rounded to 10 % of the applied dose (tested for monocetyl phosphate and cety lalcohol and in line with values estimated for the other 2 substances). With regard to oral absorption a qualitative estimation indicates bioavailability of the substance and a quantitative figure of oral absorption of 30-40 % was determined for cetyl alcohol. The pathways involved in metabolism for the 3 substances are comparable. The substances will most likely either be excreted as glucuronic acid derivatives or incorporated into normal catabolism. This conclusion is supported by the known metabolism of cetyl alcohol.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

10

Additional information

TOXICOKINETIC STATEMENT

The registered material is a multi-constituent substance consisting of monocetyl phosphate, dicetyl phosphate and cetyl alcohol.

1) Absorption, distribution, and excretion

monocetyl phosphate: Experimental data on oral absorption are not available. The molecular weight of the substance (360.4 g/mol) and the water solubility (213 mg/L in water but considerably lower in cell culture media (Bausch & Pappa 2009) with defined salt content) would suggest bioavailability. In an in vitro dermal absorption study the penetration of 14C-labelled monocetyl phosphate was investigated using rat and pig skin. Most of the radioactivity could be washed off or was found in the horny layer. Between 5.2 and 9.0 % were considered to be systemically available (Klecak 1987).

With regard to dicetyl phosphate, there is no experimental information available. However, based on the high molecular weight of 546.84 g/mol and predicted high logP of 14.68, absorption from both the GIT and the skin is considered to be low.

Orally administered 14C-labelled cetyl alcohol at a dose level of 0.7 and 1000 mg/kg bw in corn oil to rat was systemically available. About 30-40 % of the radioactivity were detected in urine, expired air, residual carcass, lymph and liver. Whereas the remaining 60-70 % were recovered from feces (Baxter et al 1967). Other data showed that radiolabelled cetyl alcohol is absorbed from the GIT mainly via lymph (63-95 %) (CIR 1988). In an in vivo dermal penetration study using hairless mice, dermal penetration using 14C-labelled cetyl alcohol was maximally of 3 %* of the applied dose (Iwata et al 1987).

In conclusion, dermal penetration is considered to be 9 % rounded 10 % of the applied dose thereby using the most conservative figure. With regard to oral absorption mainly qualitative estimates indicate bioavailability of the substance. The only quantitative figure with regard to oral absorption is the 30-40 % figure from the study on cetyl alcohol which is in line with the default factor of 50 % when no experimental data is available. Thus, a 50 % figure can be used for oral absorption. Metabolism was predicted using Meteor knowledge base Meteor 11.0.0_24_09_2008. The resulting predictions are summarised in the table below:

Predicted metabolism pathways

Metabolism Step	Likelihood	Educt	Product and further metabolites
phosphoric acid ester hydrolysis	Probable	Cetyl phosphate, dicetyl phosphate	Phosphate and cetyl alcohol Phosphate and cetyl phosphate
Hydroxylation terminal C	Probable	Cetyl phosphate, cetyl alcohol, dicetyl phosphate, cetyl chloride	Primary alcohol (i)                  conjugation with glucuronic acid (ii)                oxidation to carboxylic acidà a.      beta oxidation b.     conjugation with glucuronic acid
Hydroxylationw-1 C	Probable	Cetyl phosphate, cetyl alcohol, dicetyl phosphate, cetyl chloride	Secondary alcoholà (i)                  conjugation with glucuronic acid (ii)                oxidation to respective ketone
Conjugation of primary alcohol with glucuronic acid	Probable	Cetyl alcohol

 

2.2) Experimental data: During absorption cetyl alcohol is oxidized to palmitic acid and incorporated into triglycerides and phospholipids. Approximately 15 % of the alcohol was unchanged during its passage through mucosal cells. It should be noted that palmitic acid can be interconverted to cetyl alcohol and vice versa. This interconversion takes place during passage through the intestinal mucosal cells. Cetyl alcohol was also excreted in the urine as conjugated glucuronic acid and expired as carbon dioxide (CIR 1988).

Overall, one may conclude that the pathways involved in metabolism for the 3 substances are comparable. The substances will most likely either be excreted as glucuronic acid derivatives or incorporated into normal catabolism. This conclusion is supported by known metabolism of cetyl alcohol (CIR 1988).

References

CIR (1988) Cosmetic Ingredient Review Final Report on the Safety Assessment of Cetearyl Alcohol, Cetyl Alcohol, Isostearyl Alcohol, Myristyl Alcohol, and Behenyl Alcohol, Journal of the American College of Toxicology 7(3):359-413.

Iwata Y, Moriya Y, Kobayashi T (1987) Percutaneous absorption of aliphatic compounds, Cosmet Toiletries 102(2): 53-68

Klecak G (1987) Penetration studies in vitro on intact skin of naked rat and domestic pig skin, Hoffmann-La Roche Ltd, Basle, Switzerland, Study No. 46a/PEN/87, DSM Internal Document

Pappa G, Bausch J (2009) Amphisol K (CAS No. 19035-79-1) Waiving Statement /In vitro/ Mammalian Genotoxicity Study, DSM Nutritional Products Ltd

Baxter JH, Steinberg D, Mize CE, Avigan J (1967) Absorption and metabolism of uniformly 14C-labeled phytol and phytanic acid by the intestine of the rat studied with thoracic duct cannulation, Biochimica et Biophysica Acta 137: 277-290