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.
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]
^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.
PMID8405372.
S2CID23853321.
^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 (1): 49–60.
doi:
10.1016/S1383-5718(99)00091-1.
PMID10477339.
^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.
PMID6967495.
^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.
PMID1919875.
^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.
PMID8859281.
^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.
PMID9920441.