Padimate O is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 related to the water soluble compound PABA

4-Aminobenzoic acid

4-Aminobenzoic acid is an organic compound with the formula H2NC6H4CO2H. PABA is a white grey crystalline substance that is only slightly soluble in water...

 (4-aminobenzoic acid) that is used as an ingredient in some sunscreen

Sunscreen

Sunblock is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet radiation on the skin exposed to sunlight and thus helps protect against sunburn...

s. This yellowish water-insoluble oily liquid is an ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 formed by the condensation

Condensation reaction

A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of 2-ethylhexanol

2-Ethylhexanol

2-Ethylhexanol is a fatty alcohol, an organic compound is a branched, eight-carbon chiral alcohol. It is a colorless liquid that is nearly insoluble in water but soluble in most organic solvents...

 with dimethylaminobenzoic acid. Other names for padimate O include 2-ethylhexyl 4-dimethylaminobenzoate, Escalol 507, octyldimethyl PABA, and OD-PABA.

Photobiology

Padimate O has been implicated in the sunscreen controversy

Sunscreen controversy

Sunscreen protects against two common forms of skin cancer, squamous cell carcinoma and basal cell carcinoma , and several sunscreen ingredients protect against tumor development in photocarcinogenicity tests in mice...

. Padimate O absorbs ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 rays, thereby preventing direct DNA damage

Direct DNA damage

Direct DNA damage can occur when DNA directly absorbs the UV-B-photon. UVB light causes thymine base pairs next to each other in genetic sequences to bond together into thymine dimers, a disruption in the strand, which reproductive enzymes cannot copy...

 by UV-B. However, the thus excited padimate O molecule may then react with DNA to produce indirect DNA damage

Indirect DNA damage

Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly. Molecules that do not have this ability have a long lived excited state. This long lifetime leads to a high probability...

, similar to the effects of ionizing radiation. An in vitro

In vitro

In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

yeast study conducted in 1993 demonstrated the sunlight-induced mutagen

Mutagen

In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...

icity of padimate O. The photobiological properties of padimate O resemble those of Michler's ketone

Michler's ketone

Michler’s ketone is an organic compound with the formula of [2NC6H4]2CO. This electron-rich derivative of benzophenone is an intermediate in the production of dyes and pigments, for example Methyl violet. It is also used as a sensitizer...

 which is considered photocarcinogenic in rats and mice. These findings suggest that padimate O might also be photocarcinogenic.

However, multiple in vivo

In vivo

In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...

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.