2-ethylhexyldimethyl paba

2-Ethylhexyldimethyl PABA, chemical formula: C17H27NO2, also called Padimate O or Arlatone UVB, is an organic compound, a yellowish water insoluble oily liquid related to the water soluble compound PABA (4-aminobenzoic acid), which is used as an ingredient in many sunscreens under the name Padimate O. Chemically, 2-ethylhexyldimethyl PABA is an ester formed by condensation of 2-ethylhexanol with dimethylaminobenzoic acid. It is used in cosmetics (sunscreens, shampoos, conditioners, hair sprays, make-up, skin cleansing products.

Effect:

2-Ethylhexyldimethyl PABA absorbs ultraviolet rays in the UVB range (280-320nm) and thus prevents direct damage to DNA by UV-B. However, the excited 2-ethylhexyldimethyl PABA molecule can react with DNA and is then able to cause indirect DNA damage, similar to the effects of ionizing radiation.

Little is known about the effect of the sunlight-induced transformation products of the aminobenzoates on both the organism and the environment. In any case, UVB/UVA irradiation, photolysis and indirect phototransformation by dealkylation, hydroxylation and oxidation leads to the formation of numerous degradation products whose effects on the environment are largely unknown (Calzaa P et al. 2016).

An in vitro yeast study carried out in 1993 showed the sunlight-induced mutagenicity of Padimat O. These results suggest that Padimat O could also be a photocarcinogen (Knowland J et al. 1993).

Organic light protection filters are all those UV filters whose effect is not exclusively based on the inorganic, physically active substances titanium dioxide or zinc oxide. Organic, also known as chemical UV filters, are photoactive substances that are able to absorb light quanta in a certain wavelength range (ultraviolet radiation in the range of about 280 to 400 nm = ultraviolet radiation = UVB/UVA spectrum). The absorbed UV is then released as thermal energy without penetrating the skin. In this reversible photoisomerization, the energy of the absorbed photon must correspond to the energy required to lift an electron in the molecule of the filter substance from a lower to a higher orbit. In order to protect over the entire width of the wavelengths relevant to humans from 290 to 400 nm, several chemical filters with different absorption maxima are usually combined. With a suitable combination of organic and physical filters, the content of organic filters can also be reduced with the same UV protection. This is desirable, since especially photounstable organic UV filters can cause phototoxic and photoallergic reactions depending on their concentration in the finished product.

1. Calzaa P et al (2016) Study of the photochemical transformation of 2-ethylhexyl 4-(dimethylamino)benzoate (OD-PABA) under conditions relevant to surface waters . Water Research 88: 235-244
2. Knowland J et al (1993) Sunlight-induced mutagenicity of a common sunscreen ingredient. FEBS Letters 324: 309-313