Singlet oxygen photogeneration by ethanolic extract of Syzygium cumini fruits: Theoretical elucidation through excited states computations

The ethanolic extract of Syzygium cumini fruits was characterized and evaluated in the photogeneration of singlet oxygen (O-1(2)) under visible light radiation. This process was studied from a theoretical approach by the survey of the generated electronic excited states, after photoexcitation of the most abundant anthocyanin of the extract, i.e. delphinidin-3,5-diglucoside. It was determinated that the adiabatic energy of the optimized T-1(pi(H-1) -> pi(L)*) state was 1.55 eV and that the overall energy transfer releases similar to 0.58 eV in an exothermic process. Therefore, this state is the responsible of promoting electron transfer reactions and subsequent formation of O-1(2) through illumination.