On the Photosensitizing Properties of Aloe-Emodin in Photodynamic Therapy: Insights from the Molecular Modeling.

The photosensitizing properties of aloe-emodin were investigated under physiological conditions using computational chemistry tools. The neutral and monoanionic species were found to coexist in a 98:2 ratio, with dissociation causing a redshift in the absorption spectrum. Aloe-emodin exhibits high two-photon absorption cross-section values within the therapeutic window and significant transition probabilities, making it an efficient two-photon photosensitizer. Excited-state dynamics analysis revealed a triplet state quantum yield of 0.51 for the neutral species and around 0.88-0.89 for the anionic species, with triplet lifetimes of 26.0 s and 0.66 s, respectively. Both species exhibit similar Type I photoreactivity, but the neutral form more effectively oxidizes biomolecules during Type III photoreactivity. Additionally, the neutral species intercalates into DNA, particularly at the AT-TA site, inducing absorption changes and structural nucleotide rearrangements. The computational results align closely with available experimental data, further confirming their reliability.