Avobenzone (
trade names Parsol 1789, Milestab 1789, Eusolex 9020, Escalol 517, Neo Heliopan 357 and others,
INCI The International Nomenclature of Cosmetic Ingredients, abbreviated INCI, are the unique identifiers for cosmetic ingredients such as waxes, oils, pigments, and other chemicals that are assigned in accordance with rules established by the Personal C ...
Butyl Methoxydibenzoylmethane) is an oil-soluble ingredient used in
sunscreen products to absorb the full spectrum of
UVA
UVA most often refers to:
* Ultraviolet A, a type of ultraviolet radiation
* University of Virginia, a public research university in Charlottesville, Virginia, United States
Uva or UVA may also refer to:
Places
* Uva, Missouri, an unincorpora ...
rays.
History
Avobenzone was patented in 1973 and was approved in the EU in 1978. It was approved by the
FDA in 1988.
Properties
Pure avobenzone is a whitish to yellowish crystalline powder with a weak odor,
dissolving in
isopropanol,
dimethyl sulfoxide, decyl oleate, capric acid/caprylic, triglycerides and other oils. It is not soluble in water.
Avobenzone is a
dibenzoylmethane
Dibenzoylmethane (DBM) is an organic compound with the formula (C6H5C(O))2CH2. DBM is the name for a 1,3-diketone, but the compound exists primarily as one of two equivalent enol tautomers. DBM (actually its enol) is a white solid. Due to their ...
derivative. Avobenzone exists in the ground state as a mixture of the enol and keto forms, favoring the chelated enol.
This enol form is stabilized by intramolecular hydrogen-bonding within the β-diketone. 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.
Safety
Avobenzone, a petroleum-based sunscreen active ingredient, is not generally recognised as safe and effective by the FDA. A recent 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 acid
Aromatic acids are a type of aromatic compound. Included in that class are substances containing an aromatic ring and an organic acid functional group.
There are several categories of aromatic acids including:
*Phenolic acids
Phenolic acids or ph ...
s,
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...
s,
phenols, and
acetophenone
Acetophenone is the organic compound with the formula C6H5C(O)CH3. It is the simplest aromatic ketone. This colorless, viscous liquid is a precursor to useful resins and fragrances.
Production
Acetophenone is formed as a byproduct of the cumene p ...
s which can cause adverse health effects.
Countries with states or areas that have banned avobenzone: red. Considering ban: yellow.
Japan. Hawaii, United States of America. Marine Parks, Thailand. Palau. Nature reserves, Mexico. Virgin Islands, United States of America. Bonaire.
Brazil and the EU are considering a ban
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.
Avobenzone has been shown to degrade significantly in light, resulting in less protection over time. The UV-A light in a day of sunlight in a temperate climate is sufficient to break down most of the compound. Data presented to the
Food and Drug Administration by the
Cosmetic, Toiletry and Fragrance Association indicates a −36% change in avobenzone's UV absorbance following one hour of exposure to sunlight. This degradation can be reduced by using a photostabilizer, like
octocrylene
Octocrylene is an organic compound used as an ingredient in sunscreens and cosmetics. It is an ester formed by the condensation of 2-ethylhexyl cyanoacetate with benzophenone. It is a viscous, oily liquid that is clear and colorless.
The exten ...
. Other photostabilizers include:
*
4-Methylbenzylidene camphor
Enzacamene (INN; also known as 4-methylbenzylidene camphor or 4-MBC) is an organic camphor derivative that is used in the cosmetic industry for its ability to protect the skin against UV, specifically UV B radiation. As such, it is used in sunscr ...
(
USAN
280px, "Samguk Sagi" Book 04. Silla's Records. In 512, Usan-guk(于山國)was Ulleungdo(鬱陵島)
Usan-guk, or the State of Usan, occupied Ulleung-do and the adjacent islands during the Korean Three Kingdoms period. According to th ...
Enzacamene)
* Tinosorb S (USAN
Bemotrizinol
Bemotrizinol ( INN/ USAN, INCI bis-ethylhexyloxyphenol methoxyphenyl triazine) is an oil-soluble organic compound that is added to sunscreens to absorb UV rays. It is marketed as Parsol Shield, Tinosorb S, and Escalol S.
Bemotrizinol is a broad ...
, INCI Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine)
* Tinosorb M (USAN
Bisoctrizole
Bisoctrizole (INN/USAN, marketed by BASF as Tinosorb M, by DSM Nutritional Products as Parsol Max , by Everlight Chemical as Eversorb M, and by MPI as Milestab 360, INCI methylene bis-benzotriazolyl tetramethylbutylphenol) is a phenolic benzotri ...
, INCI Methylene Bis-Benzotriazolyl Tetramethylbutylphenol)
* Butyloctyl Salicylate (Tradename HallBrite BHB
* Hexadecyl Benzoate
* Butyloctyl Benzoate
* HallBrite PSF (INCI Undecylcrylene DimethiconeE)
* Mexoryl SX (USAN
Ecamsule
Ecamsule ( USAN, trade name Mexoryl SX, INCI terephthalylidene dicamphor sulfonic acid) is an organic compound which is added to many sunscreens to filter out UVA rays. It is a benzylidene camphor derivative, many of which are known for their exce ...
, INCI Terephthalylidene Dicamphor Sulfonic Acid)
* Synoxyl HSS (INCI Trimethoxybenzylidene Pentanedione)
* Corapan TQ (INCI Diethylhexyl 2,6-Naphthalate)
* Parsol SLX (INCI Polysilicone-15)
* Oxynex ST (INCI Diethylhexyl Syringylidene Malonate
* Polycrylene (INCI Polyester-8)
* SolaStay S1 (INCI Ethylhexyl Methoxycrylene)
*Octyl Salicylate (INCI Ethylhexyl Salicylate)
Complexing avobenzone with
cyclodextrin
Cyclodextrins are a family of cyclic oligosaccharides, consisting of a macrocyclic ring of glucose subunits joined by α-1,4 glycosidic bonds. Cyclodextrins are produced from starch by enzymatic conversion. They are used in food, pharmaceutical, ...
s may also increase its photostability. 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.
The photostability of avobenzone is further increased when sunscreens are formulated with antioxidant compounds.
Mangiferin,
glutathione
Glutathione (GSH, ) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, per ...
,
ubiquinone
Coenzyme Q, also known as ubiquinone and marketed as CoQ10, is a coenzyme family that is ubiquitous in animals and most bacteria (hence the name ubiquinone). In humans, the most common form is coenzyme Q10 or ubiquinone-10.
It is a 1,4-benzo ...
,
vitamin C,
vitamin E
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vit ...
,
beta-carotene and
trans-resveratrol
Resveratrol (3,5,4′-trihydroxy-''trans''-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacteria or fungi. Source ...
have all demonstrated some ability to protect avobenzone from photodegradation. 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." 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. A manganese doped titanium dioxide may be better than undoped titanium dioxide to improve avobenzone's stability.
Various
As an enolate, avobenzone forms with heavy metal ions (such as
Fe3+) colored complexes, and
chelating agents
Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands a ...
can be added to suppress them.
Stearates, aluminum, magnesium and zinc salts can lead to poorly soluble precipitates.
Manufacturers also recommend to avoid the inclusion of iron and ferric salts,
heavy metals
upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead
Heavy metals are generally defined as ...
, formaldehyde donors and
PABA and PABA esters. The makers of Coppertone advise that avobenzone binds iron and can cause staining of clothes washed in iron-rich water. The staining properties of sunblock made with avobenzone are particularly noticeable on fiberglass boats with white gelcoat.
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.
Absorbance Spectrum
Avobenzone has a peak absorbance around 360 nm when dissolved. The peak may shift slightly depending on the solvent.
Preparation
The compound is prepared by reacting
4-tert-butylbenzoic methyl ester (from
4-tert-butylbenzoic acid by
esterification with methanol) with
4-methoxyacetophenone
Acetanisole is an aromatic chemical compound with an aroma described as sweet, fruity, nutty, and similar to vanilla. In addition Acetanisole can sometimes smell like butter or caramel.
Acetanisole is found naturally in castoreum, the glandula ...
in
toluene in the presence of
sodium amide via
Claisen condensation
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. It is named after Rain ...
.
According to a recent patent application,
yields of up to 95% are obtained with the same starting materials in toluene in the presence of
potassium methoxide
Potassium methoxide is the alkoxide of methanol with the counterion potassium and is used as a strong base and as a catalyst for transesterification, in particular for the production of biodiesel.
Preparation
The preparation of potassium meth ...
.
It is subject to
keto-enol tautomerism
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The ter ...
and exists predominantly
enol
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The ter ...
when dissolved. Upon UV radiation, it may convert to keto form, while converting back to enol form after placing in dark.
See also
*
Sun protection factor
Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that mainly absorbs, or to a much lesser extent reflects, some of the sun's ultraviolet (UV) radiation and thus helps protect against sunburn and ...
Notes
{{Sunscreening agents
Aromatic ketones
Piceol ethers
Sunscreening agents
Tert-butyl compounds