Padimate O

Padimate O is an organic compound related to the water-soluble compound PABA (4-aminobenzoic acid) that is used as an ingredient in some sunscreens. This yellowish water-insoluble oily liquid is an ester formed by the condensation of 2-ethylhexanol with dimethylaminobenzoic acid. Other names for padimate O include 2-ethylhexyl 4-dimethylaminobenzoate, Escalol 507, octyldimethyl PABA, and OD-PABA.

Padimate O
Names
IUPAC name
2-ethylhexyl 4-(dimethylamino)benzoate
Other names
2-ethylhexyl dimethyl PABA
Escalol 507
Sundown
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.040.248
KEGG
PubChem CID
UNII
CompTox Dashboard (EPA)
Properties
Chemical formula
 C17H27NO2
Molar mass 277.408 g·mol−1
Density 0.99 g/cm3
Melting point <25 °C
Boiling point 362 °C (684 °F; 635 K)
Hazards
NFPA 704 (fire diamond)
1
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Photobiology

Padimate O absorbs ultraviolet rays, thereby preventing direct DNA damage by UV-B. However, the thus-excited padimate O molecule may then react with DNA to produce indirect DNA damage, similar to the effects of ionizing radiation. An in vitro yeast study conducted in 1993 demonstrated the sunlight-induced mutagenicity of padimate O.[1] The photobiological properties of padimate O resemble those of Michler's ketone, which is considered photocarcinogenic in rats and mice. These findings suggest that padimate O might also be photocarcinogenic.[2]

However, multiple in vivo studies conducted in hairless mice following topical application of padimate O have demonstrated no carcinogenic effects and that padimate O reduces the number of and delays the appearance of UV-induced skin tumors.[3][4][5][6]

See also
  • Padimate A, a related sunscreen ingredient
  • Sunscreen controversy.

References
  1. Knowland, John; McKenzie, Edward A; McHugh, Peter J; Cridland, Nigel A (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient". FEBS Letters. 324 (3): 309–13. doi:10.1016/0014-5793(93)80141-G. PMID 8405372.
  2. Gulston, Melanie; Knowland, John (1999). "Illumination of human keratinocytes in the presence of the sunscreen ingredient Padimate-O and through an SPF-15 sunscreen reduces direct photodamage to DNA but increases strand breaks". Mutation Research/Genetic Toxicology and Environmental Mutagenesis. 444: 49–60. doi:10.1016/S1383-5718(99)00091-1. PMID 10477339.
  3. Kligman, Lorraine H.; Akin, Frank J.; Kligman, Albert M. (1980). "Sunscreens prevent ultraviolet photocarcinogenesis". Journal of the American Academy of Dermatology. 3 (1): 30–5. doi:10.1016/S0190-9622(80)80221-0. PMID 6967495.
  4. Bissett, Donald L.; McBride, James F.; Hannon, Daniel P.; Patrick, Larry F. (1991). "Time-dependent decrease in sunscreen protection against chronic photodamage in UVB-irradiated hairless mouse skin". Journal of Photochemistry and Photobiology B: Biology. 9 (3–4): 323–334. doi:10.1016/1011-1344(91)80169-I.
  5. Bissett, Donald L; McBride, James F (1996). "Synergistic topical photoprotection by a combination of the iron chelator 2-furildioxime and sunscreen". Journal of the American Academy of Dermatology. 35 (4): 546–9. doi:10.1016/S0190-9622(96)90677-5. PMID 8859281.
  6. Kerr, Caroline (1998). "The effects of two UVB radiation-absorbing sunscreens on UV radiation-induced carcinogenesis, suppression of the contact hypersensitivity response and histological changes in the hairless mouse". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis. 422 (1): 161–4. doi:10.1016/S0027-5107(98)00188-2. PMID 9920441.
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