2-ethylhexyl dimethyl PABA
|Molar mass||277.40 g·mol−1|
|Melting point||<25 °C|
|Boiling point||362 °C (684 °F; 635 K)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
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 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. 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.
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.
- 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.
- 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. doi:10.1016/S1383-5718(99)00091-1.
- 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.
- 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. doi:10.1016/1011-1344(91)80169-I.
- 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.
- 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.