A Comparative Study between Onion Peel Extracts, Free and Complexed with β-Cyclodextrin, as a Natural UV Filter to

Mariana A Messias1,2, Sara M Ferreira1,2, Loleny Tavares3,4,5

  • 1LEPABE-Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty de Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.

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UV–Vis Spectrum

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UV–Vis Spectroscopy of Conjugated Systems

Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
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UV–Vis Spectroscopy: Woodward–Fieser Rules

UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a given structure by adding the contributions...
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