Title: Ensulizole
CAS Registry Number: 27503-81-7
CAS Name: 2-Phenyl-1H-benzimidazole-5-sulfonic acid
Additional Names: phenylbenzimidazole sulfonic acid
Trademarks: Eusolex 232 (Merck KGaA); Neo Heliopan Hydro (Symrise); Parsol HS (DSM)
Molecular Formula: C13H10N2O3S
Molecular Weight: 274.30
Percent Composition: C 56.92%, H 3.67%, N 10.21%, O 17.50%, S 11.69%
Literature References: UV-B filter in sunscreens and cosmetics. Synergistic increase in SPF occurs in combination with oil-soluble UV absorbers. Prepn: V. G. Sayapin et al., Khim. Geterotsikl. Soedin. 5, 681 (1970), C.A. 73, 45409p (1970). See also: U. Heywang et al., US 5473079 (1995 to Merck Patent GmbH). DNA photosensitization study: C. Stevenson, R. J. H. Davies, Chem. Res. Toxicol. 12, 38 (1999). Photochemical studies: J. J. Inbaraj et al., Photochem. Photobiol. 75, 107 (2002). Fluorometric determn in urine: M. T. Vidal et al., Talanta 59, 591 (2003). Complexation with cyclodextrins: S. Scalia et al., Eur. J. Pharm. Sci. 22, 241 (2004).
Properties: mp 410° (dec). Absorption max (phosphate buffer, pH 7.4): 300 nm. Soly in water: ~0.03%.
Melting point: mp 410°
Absorption maximum: Absorption max (phosphate buffer, pH 7.4): 300 nm
Derivative Type: Sodium salt
CAS Registry Number: 5997-53-5
Molecular Formula: C13H9N2NaO3S
Molecular Weight: 296.28
Percent Composition: C 52.70%, H 3.06%, N 9.46%, Na 7.76%, O 16.20%, S 10.82%
Properties: Soly: water >30%; 1,2-propylene glycol >20%.
Therap-Cat: Ultraviolet screen.
Keywords: Ultraviolet Screen.
Enterogastrone Enterolactone Enteromycin Entprol Enviomycin

Phenylbenzimidazole sulfonic acid
Skeletal formula
Space-filling model
CAS number 27503-81-7 YesY
PubChem 33919
ChemSpider 31267 YesY
KEGG D10005 YesY
Jmol-3D images Image 1
Molecular formula C13H10N2O3S
Molar mass 274.30 g/mol
MSDS Cole Parmer Material Safety Data Sheet
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Phenylbenzimidazole sulfonic acid (C13H10N2O3S) is a common sunscreen agent. In 1999, the United States Food and Drug Administration regulated that the name ensulizole be used on sunscreen labels in the United States. Phenylbenzimidazole sulfonic acid is primarily a UVB protecting agent providing only minimal UVA protection. The scope of UVB is 290 to 340 nanometers whereas the UVA range is 320 to 400 nanometers.[1] For better UVA protection, it must be paired with avobenzone, titanium dioxide, or zinc oxide; outside of the United States it can also be paired with Tinosorb [disambiguation needed] and Mexoryl [disambiguation needed]. Because phenylbenzimidazole sulfonic acid is water-soluble, it has the characteristic of feeling lighter on skin. As such, it is often used in sunscreen lotions or moisturizers whose aesthetic goal is a non-greasy finish.[2] The free acid is poorly soluble in water, so it is only used as its soluble salts.[3]