Abstract
A new Phi-order kinetic method was proposed in this study for the investigation of trans-cis photoisomerization reaction of Oxyresveratrol (ORVT) subjected to non-isosbestic irradiation. In ethanolic media, it has been proven that forward (Phi(lambda irr)(A -> B) )and reverse (Phi(lambda irr)(B -> A)) reaction quantum yields were dependent on the monochromatic irradiation wavelength according to sigmoid patterns over the spectral ranges of their electronic absorption (260360 nm). An 11.4- and 6.6-fold increases were recorded for (Phi(lambda irr)(B -> A)) and (Phi(lambda irr)(A -> B)), respectively. The efficiencies of the former (Phi(lambda irr)(B -> A), ranging between 2.3 x 10(-2) and 263 x 10(-2)) were 33 to 60% smaller than those of the respective Phi(lambda irr)(A -> B) measured at the irradiation wavelengths selected. Overall, between 57 and 97% degradation of the initial trans-ORVT was observed under relatively weak light intensities, with the highest values recorded at the longest wavelengths. These findings strongly recommend protection from light in all situations of this biologically important phytomolecule that possesses therapeutic value of interest to pharmaceutical applications. The Phi-order kinetics also offered a simple way to develop a reliable actinometric method that proved ORVT to be an efficient actinometer for the dynamic range 295-360 nm. The usefulness of Phi-order kinetics for the investigation and quantification of phytoproducts' photodegradation was discussed. (C) 2017 Elsevier B.V. All rights reserved.