Metabolism and disposition of 2-hydroxy-4-methoxybenzophenone, a sunscreen ingredient, in Harlan Sprague Dawley rats and B6C3F1/N mice; a species and route comparison

Abstract

2-Hydroxy-4-methoxybenzophenone (HMB) is a common ingredient in personal care products and used as an UV stabilizer. In these studies, disposition and metabolism of [¹⁴C]HMB in rats and mice was assessed following single gavage administration (10, 100, or 500 mg/kg), single IV administration (10 mg/kg), or dermal application (0.1, 1, 10, or 15 mg/kg).Following gavage administration, [¹⁴C]HMB was well absorbed and excreted mainly in urine (39-57%) and feces (24-42%) with no apparent difference between doses, species or sexes. Distribution of HMB in tissues was minimal in rats (0.36%) and mice (<0.55%).Distribution of HMB following dermal application was comparable to that following gavage administration; no differences between doses, sexes, or species were observed but absorption varied between dose vehicles. Light paraffin oil had the highest absorption and excretion (98% of the HMB dose absorbed).In rats, HMB slowly appeared in the systemic circulation (T_max ∼2-6 h) and had poor bioavailability (F%<1).Urine metabolites for both species and all routes included HMB, HMB-glucuronide, 2,4-dihydroxybenzophenone (DHB), DHB-glucuronide, and DHB-sulfates, and novel minor dihydroxy metabolites including 2,5-dihydroxy-4-methoxybenzophenone.In vitro hepatic metabolism in mice differed from human and in vivo metabolism especially for phase II conjugates.

Keywords: 2-hydroxy-4-methoxybenzophenone; Sunscreen; UV stabilizers; absorption; benzophenone-3; distribution; excretion; metabolism; oxybenzone.

Figure 1.

Total unabsorbed and absorbed dose 72 h following dermal administration of 10 mg/kg [¹⁴C]HMB formulated in selected vehicles to male Sprague Dawley rats. Absorbed dose is defined as total of all radioactivity recovered in excreta and tissues. Unabsorbed dose is defined as total radioactivity recover in applicator, tape/glue, and dose site swipes.

Figure 2.

A) HPLC radiochromatogram of male rat urine collected 0–72 h following 100 mg/kg single oral gavage administration of [¹⁴C]HMB, B) HPLC radiochromatogram of male rat urine collected 0–72 h following 10 mg/kg dermal administration of [¹⁴C]HMB, formulated in Coconut oil:Ethanol (1:1), C) HPLC radiochromatogram of female rat urine collected 0–72 h following 100 mg/kg single oral gavage administration of [¹⁴C]HMB, D) HPLC radiochromatogram of male mice urine collected 0–72 h following 100 mg/kg single oral gavage administration of [¹⁴C]HMB.

Figure 3.

LC-MS/MS total ion chromatogram of male rat sample following 10 mg/kg oral gavage administration of [¹⁴C]HMB (0 to 24 h Urine Composite Sample). MRM transitions: Peaks 3 and 10 = 391/137 (DHB Glucuronides), Peak 8 = 405/151 (HMB Glucuronide), Peak 14b = 245/151 (potential isomer of DHMB), and Peak 15 = 229/151 (HMB).

Figure 4.

LC-MS-MRM Chromatograms of Male Rat Urine Composite (500 mg/kg, oral gavage) A)Before Incubation, B) After Incubation with Hydrochloric Acid C) After Incubation with β-glucuronidase and sulfatase from H. pomatia, and D) After Incubation with β-glucuronidase from E. coli.

Figure 5.

Plasma free HMB concentrations vs time profile following 10 mg/kg single oral gavage or IV administration of [¹⁴C]HMB in male and female Sprague Dawley rats A-D) TK analysis of observed vs fit data using non-compartmental analysis.

Figure 6.

Postulated Metabolism of HMB in Rats and Mice