Avobenzone, also known as Parsol 1789 or butyl methoxydibenzoylmethane, is a widely used ingredient in sunscreen products due to its ability to absorb ultraviolet UV radiation, particularly in the UVA range 320-400 nm . The mechanism of action of avobenzone involves the absorption of UV radiation and its subsequent conversion into less harmful energy forms, such as heat.The photochemical properties of avobenzone can be attributed to its molecular structure, which contains a dibenzoylmethane moiety. This moiety is responsible for the compound's strong absorption of UVA radiation. When avobenzone absorbs UV radiation, it undergoes a reversible photochemical isomerization process, transitioning from its enol form the ground state to its keto form the excited state . This process involves the movement of electrons within the molecule, resulting in a change in its molecular structure.The factors that make avobenzone an efficient UV absorber include:1. Strong absorption in the UVA range: Avobenzone has a high molar absorptivity in the UVA range, which allows it to effectively protect the skin from the harmful effects of UVA radiation, such as premature aging and DNA damage.2. Reversible isomerization: The ability of avobenzone to undergo reversible isomerization allows it to return to its ground state after absorbing UV radiation, enabling it to continue absorbing UVA radiation without undergoing significant degradation.3. Conversion to less harmful energy forms: Upon absorbing UV radiation, avobenzone dissipates the absorbed energy in the form of heat, reducing the potential for harmful photochemical reactions to occur on the skin.However, it is important to note that avobenzone can be photounstable, meaning it can degrade upon exposure to sunlight, leading to a reduction in its UV-absorbing capabilities. To address this issue, avobenzone is often combined with other photostabilizing agents, such as octocrylene or ecamsule, in sunscreen formulations to enhance its stability and overall effectiveness.In summary, the mechanism of action of avobenzone involves the absorption of UVA radiation and its conversion to less harmful energy forms. Its strong absorption in the UVA range, reversible isomerization, and ability to dissipate absorbed energy as heat make it an efficient UV absorber and a popular ingredient in sunscreen products.