Oxybenzone

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: fulfill scientifical principle with well organized publication

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

To investigate the toxicokinetics and metabolism of BP-type UV filters in rats using gas chromatography–mass spectrometry (GC–MS). The metabolism of test article was examined using individual and pooled blood samples collected at various time points.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Oxybenzone

EC Number:

205-031-5

EC Name:

Oxybenzone

Cas Number:

131-57-7

Molecular formula:

C14H12O3

IUPAC Name:

2-benzoyl-5-methoxyphenol

Constituent 2

Reference substance name:

HMB

IUPAC Name:

HMB

Test material form:

not specified

Details on test material:

chemical name: 2-hydroxy-4-methoxybenzophenone (HMB)
sympot: oxybenzone
Formula: C14H12O3
Molecular weight: 228.24
CAS NO.: 131-57-7
b.p./m.p.(ºC): 150-160/66
Log Kow: 3.52

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

Animal treatments
Male Sprague–Dawley rats at 8–10weeks of age (approximately 300±25 g) were obtained from Deahan Biolink Co., LTD. (Korea). Group of 7 rats per each chemical treatment had free access to water and a standard diet (Han Lim Lab.)
Animal Co. Korea) until 24 h prior to being used for experiments, at which time only food was removed, and were kept under standard conditions (21–23 ºC, 12-h light:12-h dark cycle, relative humidity 45–55%).

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

Animals were orally administered test article (100 mg/kg body weight, bw), dissolved in corn oil. To obtain a homogeneous dosing solution, test article was ultra-sonicated in corn oil for 5min (Branson 5510, Switzerland).The dosing volume applied was 4 ml/kg bw.

Duration and frequency of treatment / exposure:

The compound was detected up to 24 h after a single administration.

Doses / concentrations

Remarks:

Doses / Concentrations:
100 mg/kg body weight, bw

No. of animals per sex per dose / concentration:

7

Control animals:

yes, concurrent no treatment

Positive control reference chemical:

no data

Details on study design:

Metabolism of test article in rats:
To detect and identify test article metabolites, we examined the toxicokinetics of typical parent compounds, in male Sprague–Dawley rats. The metabolism of test artcile was examined using individual and pooled blood samples collected at various time points.

Details on dosing and sampling:

Preparation of rat blood samples:
Plasma samples (100 µl) were thawed at room temperature, added to an equal volume of acetonitrile (100 µl), mixed by vortexing, and centrifuged at 15,000 rpm for 5 min to pellet precipitated proteins. Aliquots of the supernatant were treated with 6N HCl (200 µl) to hydrolyze bound compounds at 100 ºC for 1 h. The samples were then adjusted to pH 8.5 with borate buffer after cooling.
The deuterated internal standard (10 ppm×20 µl; 200 ng) was added to each sample. The samples were extracted into ethyl acetate, the organic phase was evaporated for dryness, and the residue was derivatized with MSTFA (50 µl,30 min at 80 ºC) for analysis by GC–MSD.

Statistics:

Toxicokinetic calculations were performed on each individual set of data using the pharmacokinetic calculation software WinNonlin Standard Edition Version 1.1 (Scientific Consulting, Apex, NC, USA) by non-compartmental method (Gabrielsson andWeiner, 1994). The following parameters were generated by the program: (i) biological half-life (t1/2), calculated fromthe slope of the terminal phase; (ii) area under the curve (AUC), where AUC was calculated to infinity according to the linear trapezoidal rule,AUC =AUC0−t +AUCt−inf. ; (iii) area under the moment curve (AUMC), where AUMC was calculated to infinity according to the linear trapezoidal rule; (iv) maximum plasma concentration (Cmax); (v) time to maximum concentration (Tmax); (vi) total body clearance (Cl), where clearance = dose/AUC; (vii) apparent volume of distribution calculated based on the terminal phase (Vz/F); and (viii) mean residence time (MRT), calculated using AUMC/AUC. The metabolite profiles of BP andHBPwere also examined by using plasma samples collected formindividual rats at various time points.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Toxicokinetic parameters

Toxicokinetic parameters 1

Toxicokinetic parameters:

Cmax: 21.21±11.61g/ml within 3 h (Tmax)

Toxicokinetic parameters 2

Toxicokinetic parameters:

half-life 1st: 4.58 ± 0.48 h

Toxicokinetic parameters 3

Toxicokinetic parameters:

AUC: 104.89±23.82g/ml h.

Toxicokinetic parameters 4

Toxicokinetic parameters:

Tmax: 2.71 ± 0.61h

Toxicokinetic parameters 5

Toxicokinetic parameters:

other: mean residence time (MRT)(h): 7.11 ± 0.80

Toxicokinetic parameters 6

Toxicokinetic parameters:

other: apparent clearance(Cl/F )(ml/h/kg) : 1.33 ± 0.32

Toxicokinetic parameters 7

Toxicokinetic parameters:

other: apparent volume of distribution(V /F) (ml/kg): 9.79 ± 2.93

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

2,4-dihydroxybenzophenone (DHB), which was formed via o-demethylation and subsequently converted into 2,3,4-trihydroxybenzophenone (THB), and 2,2-dihydroxy-4-methoxybenzophenone (DHMB), which formed via the aromatic hydroxylation of test article (i.e., type B UV filters).
Test article was analyzed as a typical type B UV filter. After oral administration, blood samples analyzed via GC–MS showed four peaks, including the parent compound and three metabolites. The two major metabolites were identified as DHB and DHMB. DHB is formed via O-dealkylation of the methoxy side chain on ring A of HMB, whereas DHMB is formed via the aromatic hydroxylation of ring B at the ortho position. A third metabolite, THB, was also present at low concentrations; this highly polar compound is formed from DHB via the aromatic hydroxylation of ring A at the meta position.

Bioaccessibility (or Bioavailability)

Bioaccessibility (or Bioavailability) testing results:

no data

Any other information on results incl. tables

In blood samples from untreated rats (prior to administration of the test compounds), the concentra- tion of parent compounds and all identified metabolites were below the limit of detection. After administration, the com- pounds were detectable up to 24 h after administration.

In this study, the toxicokinetic parameters of test article were only determined after acid hydrolysis.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): other: The concentration of these metabolites in rat blood decreased much more slowly over time compared to the parent compounds. Thus, it indicate that such metabolites might have more significant adverse effects than the parent compounds over the long term.
In conclusion, test article was enzymatically converted to at least three intermediates, including DHB, DHMB, and THB. The concentration of these metabolites in rat blood decreased much more slowly over time compared to the parent compounds.

Executive summary:

This publication was studied to investigate the toxicokinetics and metabolism of BP-type UV filters including test item in rats using gas chromatography–mass spectrometry (GC–MS) to assess their oral bioavailability and to lay groundwork for the evaluation of comparative toxicity. Based on the results given in this study, test article was enzymatically converted to at least three intermediates. 2,4-dihydroxybenzophenone (DHB), 2,3,4-trihydroxybenzophenone (THB) and 2,2-dihydroxy-4-methoxybenzophenone (DHMB) are the major metabolite forms of test article. The concentration of these metabolites in rat blood decreased much more slowly over time compared to the parent compounds.