PHOTOPHYSICAL CHARACTERIZATION OF 4-METHYLSCULETIN (4-Me) DERIVATIVE: PH-DEPENDENT SPECTRAL ANALYSIS IN AQUEOUS SOLUTION

Coumarins, a class of naturally occurring substances found in various plant species, have gained a considerable attention in biotechnology due to their anti-inflammatory, antioxidant, and antimicrobial properties. Within this group of compounds, the derivative 4-methylsculetin (4-Me) has shown remarkable promise in experimental models of intestinal inflammation, suggesting its potential as a treatment for inflammatory bowel diseases. Furthermore, 4-Me has emerged as a promising theranostic compound, displaying a unique combination of therapeutic and diagnostic properties attributed to its distinct optical characteristics. This renders it a potentially multifunctional agent capable of targeted intervention and non-invasive monitoring in diverse biomedical applications. The chemical structure of 4-Me imparts pH-dependent behavior, which may play a pivotal role in modulating its biological activity and optical emission properties within living organisms. Given the significance of understanding its optical properties in environments with varying pH levels, our study aimed to investigate the absorption and emission spectral properties of 4-Me in aqueous solutions at a fixed concentration (50 µmol.L-1) under different pH conditions, ranging from 2.0 to 12.0. By examining these specific pH values, we were able to explore the protonation-deprotonation state of 4-Me. Our findings revealed pronounced shifts in the absorption and emission spectra of 4-Me as pH increased, with bands shifting towards longer wavelengths and a considerable change in emission intensity. These results provide fundamental insights into the photophysical properties of 4-Me, shedding light on its optical behavior in varying pH environments. Understanding such characteristics is vital for deciphering its response under diverse physiological conditions within the human body, and this knowledge supports the rational design and optimization of 4-Me as potential therapeutic agent for inflammatory diseases.

This work was supported by UNESP (COPE Conecta), FAPESP (2020/15185-0 and 2018/2224-6) and CNPq (311368/2022-0).