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Photostability of the sunscreening agent 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone) in solvents of different polarity and proticity

Paper ID Volume ID Publish Year Pages File Format Full-Text
29016 44112 2008 11 PDF Available
Title
Photostability of the sunscreening agent 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone) in solvents of different polarity and proticity
Abstract

The most widely used UVA absorber in broad-spectrum sunscreens is 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone). However, the photostability of avobenzone is solvent-dependent. The aim of this work was to investigate the photostability of avobenzone in solvents of different polarity and proticity. Four solvents were employed, namely, cyclohexane, ethyl acetate, dimethylsulfoxide and methanol. The cause of the instability of avobenzone in these solvents was determined by means of UV spectroscopy, high performance liquid chromatography, gas chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The effect of oxygen on the photo-instability was also determined. Avobenzone was found to lose absorption efficacy as a result of photoisomerisation from the enol to the keto form and/or photodegradation to form photoproducts that absorb principally in the UVC region, depending on the solvent. It was found to be essentially photostable in the polar protic solvent methanol but photoisomerised in the polar aprotic solvent dimethylsulfoxide. In the nonpolar solvent cyclohexane, it photodegraded appreciably. Both photoisomerisation and photodegradation occurred to a similar extent in the moderately polar aprotic solvent ethyl acetate. Photoisomerisation occurred only in the presence of oxygen whereas photodegradation occurred irrespective of oxygen. This knowledge is important in order to achieve the correct formulation for sunscreens incorporating avobenzone.

Keywords
Avobenzone; Photostability; Solvent polarity and proticity
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Photostability of the sunscreening agent 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone) in solvents of different polarity and proticity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 200, Issues 2–3, 15 December 2008, Pages 410–420
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us