Abstract
The aim of this study was to determine the influence of the substituent groups on the photostability of eight boldine derivatives, including some oxazole and oxazinone derivatives, in order to increase the sunscreen protection properties previously demonstrated for boldine. Such derivatives showed bands similar to those of boldine in the absorption and emission spectrum. The spectroscopic properties are pH dependent. The photostability of the derivative compounds was higher than that of boldine, in accordance with the low value of the photoconsumption quantum yield determined. The low fluorescence quantum yield values observed for boldine 1 and 4 as both base and hydrochloride derivative compounds led us to postulate that these compounds are deactivated by a mechanism different to the fluorescence pathway, probably due to the electron-withdrawing inductive effect of NO for boldine 1, and to the increase of the aromatic framework for boldine 4.
Highlights
UV solar radiation has been implicated in cancer probably due to cellular damage that begins with proteins and DNA as the primary targets
There is a slight bathochromic shift in both bands at pH 3 with respect to boldine in methanol, possibly due to the solvation of the non-bonding electrons from auxochrome groups, which would diminish the n orbital energy, affecting the n- π* transitions and producing the observed shift.[21]
All boldine base derivatives in this study showed lower photoconsumption quantum yields and photodecomposition rates than boldine
Summary
UV solar radiation has been implicated in cancer probably due to cellular damage that begins with proteins and DNA as the primary targets. With the purpose of reducing the effects of UV radiation, diverse molecules have been synthesized to act as radiation filters, diminishing the radiation dose (UVA/ UVB) received by the skin in topical applications.[4,5,6] Recently, the increasing cosmetic use of solar filters has put in evidence the side effects associated with molecules used as photoprotectors.
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