PHOTOLYSIS STUDY OF OCTYL P-METHOXYCINNAMATE LOADED MICROEMULSION BY MOLECULAR FLUORESCENCE AND CHEMOMETRIC APPROACH

MARCOS GRUNHUT; DANIELLE SILVA NASCIMENTO; INSAUSTI MATIAS; FERNÁNDEZ BAND BEATRIZ; MARCOS GRUNHUT; DANIELLE SILVA NASCIMENTO; INSAUSTI MATIAS; FERNÁNDEZ BAND BEATRIZ

SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY.

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2018 p. 277 - 282

1386-1425

Octyl p-methoxycinnamate (OMC) is one of the most widely used sunscreen agents. However, the efficiency ofOMC as UV filter over time is affected due to the formation of the cis-isomer which presents a markedly lowerextinction coefficient (εcis = 12,600 L mol−1 cm−1 at 291 nm) than the original trans-isomer (εtrans =24,000 L mol−1 cm−1 at 310 nm). In this work, a novel carrier for OMC based on an oil-in-water microemulsionis proposed in order to improve the photostability of this sunscreen. The formulationwas composed of 29.2% (w/w) of a 3:1 mixture of ethanol (co-surfactant) and decaethylene glycolmono-dodecyl ether (surfactant), 1.5% (w/w) of oleic acid (oil phase) and 69.2% (w/w) of water. This microemulsion was prepared in a simple way, undermoderate stirring at 25 °C and using acceptable, biocompatible and accessiblematerials for topical use.OMCwasincorporated in the vehicle at a final concentration of 5.0% (w/w), taking into account the maximum permittedlevels established by international norms. Then, a photolysis study of the loaded formulation was performedusing a continuous flow system. The direct photolysis was monitored over time by molecular fluorescence. Therecorded spectra data between 370 y 490 nm were analyzed by multivariate curve resolution-alternating leastsquares algorithm. The kinetic rate constants corresponding to the photolysis of the trans-OMC were calculatedfromthe concentration profiles, resulting in 0.0049 s−1 for the trans-OMC loaded microemulsion and 0.0131 s−1for the trans-OMC in aqueous media. These results demonstrate a higher photostability of the trans-OMC whenloaded in the proposed vehicle with respect to the free trans-OMC in aqueous media.