{"id":2232,"date":"2015-03-27T08:00:50","date_gmt":"2015-03-27T14:00:50","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=2232"},"modified":"2023-06-06T12:44:51","modified_gmt":"2023-06-06T18:44:51","slug":"pcc-avobenzone-globally-approved-uva-absorber","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/2232\/pcc-avobenzone-globally-approved-uva-absorber\/","title":{"rendered":"Avobenzone: A Globally Approved UVA Absorber"},"content":{"rendered":"

Avobenzone is the most important UVA absorber that has been globally approved. Avobenzone<\/a> (EU<\/a>) (formally 4-tert-butyl-4′-methoxydibenzoylmethane, or butyl methoxydibenzoylmethane) was patented in 1973 and commercialized by Hoffman LaRoche as Parsol 1789.<\/p>\n

It was approved as a monographed sunscreen in the EU (up to 5%) in 1978 and by the FDA (up to 3%) in 1996. It is an oil-soluble, crystalline UVA sunscreen<\/a> (EU<\/a>) with a melting point of 81-86 C. Avobenzone has an absorption maximum of 357 nm and a UV absorption value (1% \/ 1 cm in methanol<\/a> (EU<\/a>) at 358 nm) of 1100 \u2013 1160.<\/p>\n

\"Active
Active enol form of avobenzone.<\/figcaption><\/figure>\n

Avobenzone is a dibenzoylmethane derivative for which the ground state is a mixture of the enol\/ keto forms. Only the enol form is an\u00a0effective UVA absorber. When irradiated with UVA light, it generates a triplet excited state in the keto form that can cause the avobenzone to degrade, as well as cause deep-level skin damage. Avobenzone can lose up to 36% of its potential for UV absorption after only 1 hour of exposure to sunlight, if not stabilized.<\/p>\n

Stabilizing Avobenzone<\/h3>\n

Perhaps the best approach to stabilizing avobenzone is to incorporate octocrylene<\/a> (EU<\/a>) in the formulation to help prevent the formation of the triplet state. Octocrylene is also a globally approved sunscreen (although some evidence suggests octocrylene may itself be a photo-sensitizer, causing indirect DNA damage). The key L\u2019Oreal patents (in the United States) for stabilization of avobenzone using octocrylene expired in late 2014 and are now freely available.<\/p>\n

This approach can help you formulate avobenzone with octinoxate, which can react with avobenzone via a 2+2 cycloaddition reaction to form a non-absorbing chemical. Titanium<\/a> (EU<\/a>) and zinc oxide<\/a> (EU<\/a>) can have a negative effect on avobenzone stability unless properly coated. However, these combinations aren\u2019t permitted in the U.S. under the current U.S. monograph.<\/p>\n

Metals such as iron<\/a> (EU<\/a>), aluminum<\/a> (EU<\/a>), or zinc<\/a> (EU<\/a>) can cause discoloration, loss of UV absorption, and reduced solubility if not complexed. Chelating agents should also be used to prevent this type of interaction with multivalent metals. Formaldehyde<\/a> (EU<\/a>) donating preservatives should also be avoided.<\/p>\n

Recommended Photo Stabilizers:<\/h4>\n