Abstract
The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.
Highlights
Biological systems depend on solar radiation for energy to sustain life
Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol
Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens
Summary
Biological systems depend on solar radiation for energy to sustain life. chronic exposure to solar ultraviolet radiation (UVR) is responsible for health problems such as premature aging, erythema, skin cancers and sunburn [1] [2] [3] [4] [5]. Attention has been shifted towards the use of sunscreens which in addition to the screening of detrimental UVR have photoprotection constituents [6] Antioxidants efficiently serve this purpose, since they scavenge UV-induced free radicals [2] [7]. The structural features of drometrizole (pi-conjugation, presence of hydroxyl group) and its above-mentioned properties warrant it to be a potent antioxidant-UV filter Such a study is conveniently achieved via the use of density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The effects of an electron-donating substituent (EDS) and an electron-accepting substituent (EAS) (see Figure 1) on the antioxidant activity and UV spectra of PBT were assessed The effects of these substituents were explored with the intention of improving their anti-oxidant efficiencies. This study will serve as a base to create an awareness of the photoprotective properties of the compounds studied possible design and applications as sunscreen products
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