Nonadiabatic dynamics Mechanisms of natural UV Photoprotection ompounds chlorogenic acid and isochlorogenic acid a: Double conjugated structures but single photoexcited channel

Abstract

In this work, we proposed the natural molecules chlorogenic acid (CA) and isochlorogenic acid A (ICAA) could be used as sunscreens for the first time. The non-radiative energy relaxation mechanisms of two molecules were presented through a combination of theoretical calculations and spectral experiments. We demonstrated that the trans-cis photoisomerization coordinate in the picosecond timescale could take place in both the natural molecules chlorogenic acid (CA) and isochlorogenic acid A (ICAA). ICAA has a double CA conjugated structure. It has been demonstrated that only one CA conjugated structure in ICAA can be photoexcited. Moreover, the photoisomerization channel of ICAA was similar to CA. We reported a dual conjugated system in a plant-derived sunscreens and the dual conjugated system improves the energy absorption efficiency to some extent. This work confirmed that the plant-derived CA and ICAA could be potential natural sunscreen molecules and created an avenue for designing novel sunscreen compounds.