Octyl methoxycinnamate or ethylhexyl methoxycinnamate or octinoxate, trade namesEusolex 2292 and Uvinul MC80, is an organic compound that is an ingredient in some sunscreens and lip balms. It is an ester formed from methoxycinnamic acid and 2-ethylhexanol. It is a liquid that is insoluble in water. It is primarily used in sunscreens and other cosmetics to absorb UV-B rays from the sun, protecting the skin from damage. It is also used to reduce the appearance of scars.
One study performed in 2000 raised safety concerns about octyl methoxycinnamate by demonstrating toxicity to mouse cells at concentrations lower than typical levels in sunscreens. However, another study concluded that octyl methoxycinnamate and other sun screening agents do not penetrate the outer skin in sufficient concentration to cause any significant toxicity to the underlying human keratinocytes. Estrogenic and neurological effects were noted in laboratory animals at concentrations close to those experienced by sunscreen users and were also shown in vitro. Octyl methoxycinnamate has been shown to be light sensitive with a decrease in UV absorption efficiency upon light exposure. This degradation causes formation of the Z-octyl-p-methoxycinnamate from the E-octyl-p-methoxycinnamate. In contrast, the OMC does not show degradation when kept in darkness for extended periods of time. A study carried out in 2017 by the Research Centre for Toxic Compounds in the Environment at Masaryk University, Czech Republic, indicates that octyl methoxycinnamate may damage human cell DNA. When exposed to sun rays, the spatial arrangement of its molecules changes and isomerisation takes place. While until now only unchanged EHMC has been researched, Massaryk University researchers focused on its isomers and found out that it has a significant genotoxic effect under lab conditions. It means that it may potentially damage human DNA and cause genome mutations which may lead to serious health risks.
Ecological impact
Concern about effects on coral reefs resulted in a bill in the state legislature of Hawaii to limit use of sunscreens containing octyl methoxycinnamate and oxybenzone. For the same reasons, the government of Palau signed a law in 2018 that restricts the sale and use of sunscreen and skincare products that contain a list of ten different chemicals, including the UV filters octyl methoxycinnamate, oxybenzone and octocrylene, with fines of USD 1000 for retailers who violate the law and the power to confiscate such products from non-commercial users.
Stereochemistry
Octinoxate contains a stereocenter and a double bond. It has the following stereoisomers. Process for producing 2-ethylhexanol: , 29 August 1985; , August 20, 1986. Therefore octinoxate could consist of the following four stereoisomers:
