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 |
EC Number |
|
KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
| |
| |
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). |
Avobenzone (trade names Parsol 1789, Milestab 1789, Eusolex 9020, Escalol 517, Neo Heliopan 357 and others, INCI Butyl Methoxydibenzoylmethane) is an organic molecule and an oil-soluble ingredient used in sunscreen products to absorb the full spectrum of UVA rays.
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]
Pure avobenzone is a whitish to yellowish crystalline powder with a weak odor, [3] dissolving in 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]
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; phenolic acids, aldehydes, phenols, and acetophenones which can cause adverse health effects. [9] [10] [11]
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. [12] [13] [14] 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. [15] For this reason, in sunscreen products, avobenzone is always formulated together with a photostabilizer, such as octocrylene. Other photostabilizers include:
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. Mangiferin, glutathione, ubiquinone, vitamin C, vitamin E, 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]
As an enolate, avobenzone forms with heavy metal ions (such as Fe3+) colored complexes, and 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]
Avobenzone has a peak absorbance around 360 nm when dissolved. The peak may shift slightly depending on the solvent.
The compound is prepared by reacting 4-tert-butylbenzoic methyl ester (from 4-tert-butylbenzoic acid by esterification with methanol) with 4-methoxyacetophenone in toluene in the presence of sodium amide via Claisen condensation. [37]
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]
See also
{{cite journal}}
: CS1 maint: DOI inactive as of December 2024 (link){{cite web}}
: CS1 maint: archived copy as title (link)Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights.
Oxybenzone or benzophenone-3 or BP-3 is an organic compound belonging to the class of aromatic ketones known as benzophenones. It takes the form of pale-yellow crystals that are readily soluble in most organic solvents. It is widely used in sunscreen formulations, plastics, toys, furniture finishes, and other products to limit UV degradation. In nature, it can be found in various flowering plants (angiosperms). The compound was first synthesised in Germany by chemists König and Kostanecki in 1906.
Sunscreen, also known as sunblock, sun lotion or sun cream, is a photoprotective topical product for the skin that helps protect against sunburn and prevent skin cancer. Sunscreens come as lotions, sprays, gels, foams, sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, sunhats and special sun protective clothing, and other forms of photoprotection.
Sunless tanning, also known as UV filled tanning, self tanning, spray tanning, or fake tanning, refers to the effect of a suntan without exposure to the Sun. Sunless tanning involves the use of oral agents (carotenids), or creams, lotions or sprays applied to the skin. Skin-applied products may be skin-reactive agents or temporary bronzers (colorants).
Ecamsule 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 excellent photostability.
Octyl methoxycinnamate or ethylhexyl methoxycinnamate (INCI) or octinoxate (USAN), trade names Eusolex 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.
UV filters are compounds, mixtures, or materials that block or absorb ultraviolet (UV) light. One of the major applications of UV filters is their use as sunscreens to protect skin from sunburn and other sun/UV related damage. After the invention of digital cameras changed the field of photography, UV filters have been used to coat glass discs fitted to camera lenses to protect hardware that is sensitive to UV light.
Padimate O is an organic compound related to the water-soluble compound PABA that is used as an ingredient in some sunscreens. This yellowish water-insoluble oily liquid is an ester formed by the condensation of 2-ethylhexanol with dimethylaminobenzoic acid. Other names for padimate O include 2-ethylhexyl 4-dimethylaminobenzoate, Escalol 507, octyldimethyl PABA, and OD-PABA.
Octocrylene is an organic compound used as an ingredient in sunscreens and cosmetics. It is an ester formed by the Knoevenagel condensation of 2-ethylhexyl cyanoacetate with benzophenone. It is a viscous, oily liquid that is clear and colorless.
Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stress caused by excess or fluctuating light conditions. Humans and other animals have also developed photoprotective mechanisms to avoid UV photodamage to the skin, prevent DNA damage, and minimize the downstream effects of oxidative stress.
Bemotrizinol 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.
Bisoctrizole is a phenolic benzotriazole that is added to sunscreens to absorb UV rays. It is a broad-spectrum ultraviolet radiation absorber, absorbing UVB as well as UVA rays. It also reflects and scatters UV.
Pyrimidine dimers represent molecular lesions originating from thymine or cytosine bases within DNA, resulting from photochemical reactions. These lesions, commonly linked to direct DNA damage, are induced by ultraviolet light (UV), particularly UVC, result in the formation of covalent bonds between adjacent nitrogenous bases along the nucleotide chain near their carbon–carbon double bonds, the photo-coupled dimers are fluorescent. Such dimerization, which can also occur in double-stranded RNA (dsRNA) involving uracil or cytosine, leads to the creation of cyclobutane pyrimidine dimers (CPDs) and 6–4 photoproducts. These pre-mutagenic lesions modify the DNA helix structure, resulting in abnormal non-canonical base pairing and, consequently, adjacent thymines or cytosines in DNA will form a cyclobutane ring when joined together and cause a distortion in the DNA. This distortion prevents DNA replication and transcription mechanisms beyond the dimerization site.
Bisdisulizole disodium is a water-soluble organic compound which is added to sunscreen products to absorb UVA rays. It is marketed by Symrise.
Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly. Molecules that do not have this ability have a long-lived excited state. This long lifetime leads to a high probability for reactions with other molecules—so-called bimolecular reactions. Melanin and DNA have extremely short excited state lifetimes in the range of a few femtoseconds (10−15s). The excited state lifetime of compounds used in sunscreens such as menthyl anthranilate, avobenzone or padimate O is 1,000 to 1,000,000 times longer than that of melanin, and therefore they may cause damage to living cells that come in contact with them.
Diethylamino hydroxybenzoyl hexyl benzoate (INCI) is an organic compound used in sunscreens to absorb UVA radiation. It is marketed as Parsol DHHB by DSM and as Uvinul A Plus by BASF. DHHB has an absorption maximum of 354 nm.
Iscotrizinol is an organic compound used in sunscreens to absorb UVB and some UVA radiation with a peak protection at 310 nm. It is one of the most photostable chemical sunscreens known today with 25 hours required to lose 10% of its SPF protection ability. It is marketed as Uvasorb HEB by 3V Sigma.
Mycosporine-like amino acids (MAAs) are small secondary metabolites produced by organisms that live in environments with high volumes of sunlight, usually marine environments. The exact number of compounds within this class of natural products is yet to be determined, since they have only relatively recently been discovered and novel molecular species are constantly being discovered; however, to date their number is around 30. They are commonly described as “microbial sunscreens” although their function is believed not to be limited to sun protection. MAAs represent high potential in cosmetics, and biotechnological applications. Indeed, their UV-absorbing properties would allow to create products derived from natural photoprotectors, potentially harmless to the environment and efficient against UV damage.
A Certified Organic Sunscreen, also known as Petrochemical-Free Sunscreen, is a third party certified sunscreen product consisting of certified and approved organic ingredients, with typically zinc oxide acting as the photo-protector. An organic sunscreen is verified and approved by a certifier to international or national organic standards, such as NSF/ANSI 305 and USDA organic, which define production and labelling requirements for personal care products containing organic ingredients. These standards are complemented by existing sunscreen regulatory bodies such as the FDA that regulate the efficacy of the sunscreen, safety and permitted ingredients. Generally speaking, sunscreen has photo-protective properties that reduce the risk of skin cancer and ageing with relation to the SPF value and proper application.
Z-Cote is a commercial zinc oxide line manufactured and owned by BASF. Due to Z-Cote's photo-protective properties it is commonly used in personal care products and sunscreens. It is available in nano, non-nano, coated and uncoated forms. Z-Cote is a derivative of zinc oxide which is Generally Recognized As Safe and Effective (GRASE) by the FDA as a nutrient, cosmetic colour additive, skin protection active ingredient and other OTC products. Manufactured zinc oxide, such as Z-Cote, is only recognised as GRASE by the FDA when it is compliant with the Good manufacturing practice (GMP) standard. The original Sunsmart and Submicro Encapsulation Technologies Z-Cote patent filed in 1991 for UV skin protection expired in 2015.