Int J Cosmet Sci. 2025;00:1–11. | 1 wileyonlinelibrary.com/journal/ics Received: 21 April 2025 | Accepted: 7 July 2025 DOI: 10.1111/ics.70012 ORIGINAL ARTICLE Photostability and phototoxicity studies of a promising UVA filter for sunscreens: 1-(2-hydroxyphenyl)-3- (4-methoxyphenyl)-1,3-propanedione Yanina Susana Minaberry 1,2,3 | Gabriel Sagrera 4 | Mora Reneé García 2,5 | María Laura Gutiérrez 2,5 | Federico Eugenio Svarc 1 © 2025 Society of Cosmetic Scientists and the Société Française de Cosmétologie. 1 DQIAQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina 2 CONICET-Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina 3 ITBA: Instituto Tecnológico de Buenos Aires, Buenos Aires, Argentina 4 Departamento de Química Orgánica, Facultad de Química, UDELAR, Montevideo, Uruguay 5 Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina Correspondence Federico Eugenio Svarc, DQIAQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. Email: fsvarc@qi.fcen.uba.ar Funding information Consejo Nacional de Investigaciones Científicas y Técnicas, Grant/Award Number: PIP 2021-11220200102369CO and PIBAA No 28720210100949; Fondo para la Investigación Científica y Tecnológica, Grant/Award Number: PICT 2018-3831, PICT 2020-02532 and PICT Cat I 2021-32 Abstract A few years ago, the 2-hydroxy-4´-methoxy dibenzoylmethane (DBM11) molecule was synthesized and studied as a replacement for avobenzone (AVB, butyl methoxydibenzoylmethane) because of the latter's instability under UVA radiation. These studies, conducted in absolute ethanol with an estimated UV irradiance of 8,56 mW/cm 2 , demonstrated almost zero decomposition of DBM11. Thus, it is a promising candidate for use as a UVA chemical filter. However, further studies must be conducted to verify its photostability once formulated into an emulsion and to establish its toxicological profile. The first aim of this work was to scale up the synthesis of DBM11 to allow its formulation into an emulsion, which is required for the evaluation of its photostability under standardized UV irradiation conditions (close to ISO 24443), as required for sunscreen testing in the cosmetic industry. Additionally, in vitro phototoxicity assessments were conducted, with slight modifications to improve reproducibility, in accordance with OECD guidelines. These results demonstrate that DBM11 exhibits promising photostability and a favourable toxicological profile, making it a potential candidate for use as a UVA filter. KEYWORDS dibenzoyl methane derivatives, photostability, phototoxicity, safety testing, sunscreens, UVA filters Résumé Il y a quelques années, la molécule de 2-hydroxy-4’-méthoxy dibenzoylméthane (DBM11) a été synthétisée et étudiée en remplacement de l’avobenzone (AVB, butylméthoxydibenzoylméthane), en raison de l’instabilité de ce dernier sous rayonnement UVA. Ces études, menées dans de l’éthanol absolu avec une irradiance UV estimée à 8,56 mW/cm 2 , ont démontré une décomposition quasi nulle du DBM11. Il s’agit donc d’un candidat prometteur pour une utilisation en tant que filtre chimique UVA. Cependant, d’autres études doivent être menées pour vérifier sa photostabilité une fois formulée dans une émulsion et pour