Photochemistry and Photophysics of Shinorine Dimethyl Ester

Abstract

The photostability and photophysical properties of the dimethyl ester of the mycosporine-like amino acid shinorine have been experimentally evaluated in aqueous solution and in the presence of direct micelles prepared with a cationic or an anionic detergent, respectively. In comparison with shinorine, the ester molecule increases the photostability, the fluorescence quantum yield and the fluorescence lifetime in water as well as in the micellar solutions. The effects are more pronounced in sodium dodecyl sulfate solutions and suggest that the electrostatic attractions with the micellar interface contribute to limit the movement of the molecules and influence the relative rate of their deactivation channels. However, the predominance of the nonradiative decay is maintained together with the UV photoprotective ability of this atypical mycosporine species.

Unravelling photoprotection in microbial natural products

“…Given the continuing increase in skin cancer cases and recent concerns raised over current sunscreen filters such as phototoxicity and photdegradation, 9,10,13–15,66–68 unravelling photoprotection mechanisms through an intrinsic understanding of the photochemistry of both nature-based (and inspired) and artificial sunscreen filters continues to grow as a field of research. 16,27,69 Studies on exploring the synthesis and isolation of MAAs in nature provides complementary aspects of this research. 7,70,71 That being said, more work is certainly warranted.…”

Unravelling the Photoprotective Mechanisms of Nature-Inspired Ultraviolet Filters Using Ultrafast Spectroscopy

“…Recently, Orallo et al [ 136 , 137 ] have performed studies on the MAAs shinorine, porphyra-334 and shinorine dimethyl ester in micellar solutions to elucidate the photochemistry and photophysics in a closer-to-real sunscreen formulation environment. They found that the fluorescence quantum yield and lifetime were increased in micelle solutions compared to aqueous solutions; however, the main deactivation process remained via non-radiative decay.…”

“…The authors attributed both properties to the electrostatic interactions between MAAs and micelles which hinder molecular movements. Overall, Orallo et al [ 136 , 137 ] demonstrated that MAAs in micellar solutions which mimic a closer-to-real environment, with regards to sunscreen formulation, still perform as efficient UV filters which is promising for commercial applications. However, the electrostatic interactions which influence the decay mechanisms must be taken into account.…”

“…In terms of the future direction for nature-inspired UV filters, the work by Horbury et al [ 115 ] carried out on DES ( Section 2.1.3 ) and Orallo et al [ 136 , 137 ] carried out on MAAs ( Section 2.2.2 ) serve as pertinent examples of the need to study the photodynamics of potential UV filters in a closer-to-real environment. It is important that such work is continued across UV filter research in order to determine any differences between the photodynamics of the targeted molecule in solution and on a skin mimic.…”