Avobenzone Photostable Formulation: Achieves High Photostability via Triplet-Triplet Energy Transfer with Stabilizers

Introduction to Avobenone

There are many types of UV (ultraviolet) absorbers, among which benzophenone-type UV absorbers are widely used and possess significant practical research value. Avobenone (also referred to as Avobezone; hereinafter “Avobenone” is used for consistency) belongs to the benzophenone-type UV absorbers and is also an important organic synthesis intermediate.

Application:

1. Core Applications in Sunscreen Products
   • UVA Protection: Avobenzone is one of the few chemical UV absorbers capable of effectively absorbing UVA rays (320-400 nm), covering both UVA1 (340-400 nm) and UVA2 (320-340 nm) bands to provide comprehensive UVA protection.
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   • Broad-Spectrum Sunscreen: It is often used in combination with other UV filters (e.g., Octocrylene, Titanium Dioxide) to form a broad-spectrum sunscreen system, offering simultaneous protection against UVA and UVB (280-320 nm) rays.
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   • Stability Enhancement: To address Avobenzone’s susceptibility to photodegradation, its stability is improved through formulation optimization (e.g., adding photostabilizers) or encapsulation techniques.
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2. Auxiliary Roles in Formulations
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   • Improving Product Texture: As an oil-soluble ingredient, Avobenzone enhances the spreadability and skin feel of sunscreen products, making them easier to apply and absorb.
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   • Enhancing Formulation Stability: In sunscreen lotions or creams, Avobenzone synergizes with other ingredients to delay product oxidation and discoloration.
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4. Exploratory Applications in Other Fields
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   • Cosmetics: Added to foundations, BB creams, and other base makeup products to provide daily sun protection.
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   • Hair Care: Used in sunscreen sprays or conditioners to shield hair from UV damage.
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   • Textiles: Applied to sun-protective fabrics via microencapsulation technology to boost UVA resistance in clothing.

Synthesis methods:

Currently, the main methods for synthesizing Avobenone include:

① The condensation-addition-elimination-hydration method, wherein p-anisylacetone (4-methoxyacetophenone) and p-tert-butylbenzaldehyde undergo condensation, bromine addition, elimination to form an alkyne, and hydration to obtain the product, with a yield of 58%. This method has a long route, high cost, and low output;

② The Claisen ester condensation method, wherein p-anisylacetone and p-tert-butylbenzoic acid methyl ester react, with a yield of 63.6%. This method is low-cost and easy to operate but has a relatively low yield;

③ The aldehyde-ketone condensation method, wherein p-anisylacetone and p-tert-butylbenzaldehyde undergo condensation to form an alcohol, followed by oxidation, with a yield of 34.6%. This method is easy to operate but has a high cost and low output.