Avobenzone

Source: Wikipedia, the free encyclopedia.
Avobenzone
Skeletal formula of avobenzone
Space-filling model of the avobenzone molecule
Names
Preferred IUPAC name
3-(4-tert-Butylphenyl)-1-(4-methoxyphenyl)propane-1,3-dione
Other names
butylmethoxydibenzoylmethane; 4-tert-butyl-4'-methoxydibenzoylmethane
Identifiers
3D model (
JSmol
)
ChEMBL
ChemSpider
ECHA InfoCard
 100.067.779 Edit this at Wikidata
EC Number
  • 274-581-6
KEGG
UNII
  • InChI=1S/C20H22O3/c1-20(2,3)16-9-5-14(6-10-16)18(21)13-19(22)15-7-11-17(23-4)12-8-15/h5-12H,13H2,1-4H3 checkY
    Key: XNEFYCZVKIDDMS-UHFFFAOYSA-N checkY
  • InChI=1/C20H22O3/c1-20(2,3)16-9-5-14(6-10-16)18(21)13-19(22)15-7-11-17(23-4)12-8-15/h5-12H,13H2,1-4H3
    Key: XNEFYCZVKIDDMS-UHFFFAOYAG
  • O=C(c1ccc(cc1)C(C)(C)C)CC(=O)c2ccc(OC)cc2
Properties
C20H22O3
Molar mass 310.39 g/mol
Appearance colorless crystal
Supplementary data page
Avobenzone (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Avobenzone (

organic molecule and an oil-soluble ingredient used in sunscreen products to absorb the full spectrum of UVA
rays.

History

Avobenzone was patented in 1973 and was approved in the EU in 1978. It was approved by the FDA in 1988. As of 2021, the FDA announced that they do not support avobenzone as being generally recognized as safe and effective (GRASE)[1] citing the need for additional safety data. Avobenzone was banned in 2020 by the Palau government citing reef-toxicity concerns.[2]

Properties

Pure avobenzone is a whitish to yellowish crystalline powder with a weak odor,

isopropanol, dimethyl sulfoxide
, decyl oleate, capric acid/caprylic, triglycerides and other oils. It is not soluble in water.

Avobenzone is a dibenzoylmethane derivative. Avobenzone exists in the ground state as a mixture of the enol and keto forms, favoring the chelated enol.[4] This enol form is stabilized by intramolecular hydrogen-bonding within the β-diketone.[5] Its ability to absorb ultraviolet light over a wider range of wavelengths than many other sunscreen agents has led to its use in many commercial preparations marketed as "broad spectrum" sunscreens. Avobenzone has an absorption maximum of 357 nm.[6]

Safety

Avobenzone, a petroleum-based sunscreen active ingredient,[7] is not generally recognised as safe and effective (GRASE) by the FDA for lack of sufficient data to support this claim.[1] However, it is still the only FDA approved UVA filter (up to 3% concentration).[8] Avobenzone is also approved in all other jurisdictions, such as EU (up to 5%), Australia, and Japan.

A 2017 study at Lomonosov Moscow State University found that chlorinated water and ultraviolet light can cause avobenzone to disintegrate into various other organic compounds, including; aromatic acids, aldehydes, phenols, and acetophenones which can cause adverse health effects.[9][10][11]

Stability

Avobenzone is sensitive to the properties of the solvent, being relatively stable in polar protic solvents and unstable in nonpolar environments. Also, when it is irradiated with UVA light, it generates a triplet excited state in the keto form which can either cause the avobenzone to degrade or it can transfer energy to biological targets and cause deleterious effects.[4]

Avobenzone has been shown to degrade significantly in light, resulting in less protection over time.

Cosmetic, Toiletry and Fragrance Association indicates a −36% change in avobenzone's UV absorbance following one hour of exposure to sunlight.[15] For this reason, in sunscreen products, avobenzone is always formulated together with a photostabilizer, such as octocrylene
. Other photostabilizers include:

  • 4-Methylbenzylidene camphor (USAN
    Enzacamene)
  • Tinosorb S (USAN Bemotrizinol, INCI Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine)
  • Tinosorb M (USAN Bisoctrizole, INCI Methylene Bis-Benzotriazolyl Tetramethylbutylphenol)
  • Butyloctyl Salicylate (Tradename HallBrite BHB - [1])
  • Hexadecyl Benzoate
  • Butyloctyl Benzoate
  • HallBrite PSF (INCI Undecylcrylene DimethiconeE)[16]
  • Mexoryl SX (USAN Ecamsule, INCI Terephthalylidene Dicamphor Sulfonic Acid)
  • Synoxyl HSS (INCI Trimethoxybenzylidene Pentanedione)[17]
  • Corapan TQ (INCI Diethylhexyl 2,6-Naphthalate)[18]
  • Parsol SLX (INCI Polysilicone-15)[19]
  • Oxynex ST (INCI Diethylhexyl Syringylidene Malonate[20]
  • Polycrylene (INCI Polyester-8)[21]
  • SolaStay S1 (INCI Ethylhexyl Methoxycrylene)[22]
  • Octyl Salicylate (INCI Ethylhexyl Salicylate)[23]

Complexing avobenzone with cyclodextrins may also increase its photostability.[24] Formulations of avobenzone with hydroxypropyl-beta-cyclodextrin have shown significant reduction in photo-induced degradation, as well as decreased transdermal penetration of the UV absorber when used in high concentrations.[25]

The photostability of avobenzone is further increased when sunscreens are formulated with antioxidant compounds.

beta-carotene and trans-resveratrol have all demonstrated some ability to protect avobenzone from photodegradation.[26][27][28][29]
The stability and efficacy of avobenzone seems to continue to increase as a greater amount of antioxidants are added to the sunscreen.

According to some studies, "the most effective sunscreens contain avobenzone and titanium dioxide."[30][31] Avobenzone can degrade faster in light in combination with mineral UV absorbers like zinc oxide and titanium dioxide, though with the right coating of the mineral particles this reaction can be reduced.[32] A manganese doped titanium dioxide may be better than undoped titanium dioxide to improve avobenzone's stability.[33]

Various

As an enolate, avobenzone forms with heavy metal ions (such as

chelating agents can be added to suppress them. Stearates, aluminum, magnesium and zinc salts can lead to poorly soluble precipitates.[3] Manufacturers also recommend to avoid the inclusion of iron and ferric salts, heavy metals, formaldehyde donors and PABA and PABA esters.[citation needed
]

Avobenzone in sunscreen may stain clothes yellow-orange and make them sticky if washed in iron-rich water, as it reacts with iron to produce rust. The damage can be undone with a rust remover or stain remover.[34][35] The staining properties of sunblock made with avobenzone are particularly noticeable on fiberglass boats with white gelcoat.[citation needed]

Avobenzone also reacts with boron trifluoride to form a stable crystalline complex that is highly fluorescent under UV irradiation. The emission color of the crystals depends on the molecular packing of the boron avobenzone complex. The photoluminescence may also be altered by mechanical force in the solid state, resulting in a phenomenon called "mechanochromic luminescence". The altered emission color recovers itself slowly at room temperature or more swiftly at higher temperatures.[36]

Absorbance spectrum

Avobenzone has a peak absorbance around 360 nm when dissolved. The peak may shift slightly depending on the solvent.

Absorbance of 0.01 g-L avobenzone in DMSO


Preparation

The compound is prepared by reacting

4-methoxyacetophenone in toluene in the presence of sodium amide via Claisen condensation.[37]

Synthese Avobenzon
Synthese Avobenzon

According to a recent patent application,[38] yields of up to 95% are obtained with the same starting materials in toluene in the presence of potassium methoxide.

It is subject to

keto-enol tautomerism and exists predominantly enol when dissolved. Upon UV radiation, it may convert to keto form, while converting back to enol form after placing in dark.[39]

Keto-Enol-Gleichgewicht in 1,3-Diketonen

See also

  • Sun protection factor

Notes

  1. ^ a b Research, Center for Drug Evaluation and (2021-11-16). "Questions and Answers: FDA posts deemed final order and proposed order for over-the-counter sunscreen". FDA.
  2. ^ "REGULATIONS PROHIBITING REEF-TOXIC SUNSCREENS" (PDF). The Palau Government. 2020.
  3. ^ a b "Making Cosmetics®, Avobenzone". Makingcosmetics.com. Archived from the original on 2015-08-01. Retrieved 2015-07-29.
  4. ^
    PMID 18673327
    .
  5. PMID 22925908
    .
  6. S2CID 37910033
    .
  7. ^ "Why Evaluate the Sunscreen Active Oxybenzone (Benzophenone-3) for Carcinogenicity and Reproductive Toxicology or Consider it Unsafe for Human Use?" (PDF).
  8. ^ "After More Than A Decade, FDA Still Won't Allow New Sunscreens".
  9. ^ "Sunscreen creams break down into dangerous chemical compounds under the sunlight". EurekAlert!. Retrieved 2017-06-30.
  10. PMID 28500968
    .
  11. PMID 27258620
    .
  12. S2CID 29879472
    .
  13. PMID 10504439
    .
  14. PMID 15870853.{{cite journal}}: CS1 maint: DOI inactive as of February 2024 (link
    )
  15. ^ "CTFA letter re: Tentative Final Monograph for OTC Sunscreen" (PDF). Food and Drug Administration.
  16. ^ "Hallbrite® PSF". Archived from the original on 2011-10-02. Retrieved 2011-05-25.
  17. ^ RK Chaudhuri, MA Ollengo, P Singh and BS Martincigh, 3-(3,4,5-Trimethoxybenzylidene)-2,4-pentanedione: Design of a Novel Photostabilizer with In-vivo SPF Boosting Properties and Its Use in Developing Broad-spectrum Sunscreen Formulations, International Journal of Cosmetic Science, 39(1):25-35, 2017; First published 29 June 2016 | doi: 10.1111/ics.12344
  18. ^ Bonda C.; Steinberg D. C. (2000). "A new photostabilizer for full spectrum sunscreens". Cosmetics & Toiletries. 115 (6): 37–45.
  19. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2008-02-24. Retrieved 2007-12-03.{{cite web}}: CS1 maint: archived copy as title (link)
  20. S2CID 23707972
    .
  21. ^ http://www.hallstar.com/techdocs/Polycrylene&CorapanTQAvobenzoneStabilization.pdf [dead link]
  22. ^ "Product Information Sheet: SolaStay S1". The HallStar Company. Archived from the original on 2 October 2011. Retrieved 16 February 2010.
  23. S2CID 221937086
    .
  24. S2CID 40228301
    .
  25. PMID 18226883
    .
  26. PMID 26318281
    .
  27. S2CID 53291937
    .
  28. PMID 25086322
    .
  29. PMID 26159738
    .
  30. PMID 15014184
    .
  31. ^ "Sunscreen Drug Products for Over-the-Counter use; Marketing Status of Products Containing Avobenzone; Enforcement Policy" (PDF). US Food and Drug Administration. 1997-04-30. p. 23354. Archived (PDF) from the original on 2007-02-26. Retrieved 2007-06-03.
  32. ^ Stability Study of Avobenzone with Inorganic Sunscreens, Kobo Products Poster, 2001, Online version Archived May 7, 2007, at the Wayback Machine
  33. PMID 15238999
    .
  34. ^ "How to Remove Summer Stains From Your Clothes". Consumer Reports. 17 August 2022.
  35. ^ "The secret to removing sunscreen stains is this unexpected cleaning product". CNN. 18 July 2022.
  36. S2CID 30823815
    .
  37. ^ US 0 
  38. ^ US 0 
  39. doi:10.1016/j.jphotochem.2008.09.007
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