We studied the photophysical properties of trans-resveratrol and its main photochemical products, cis-resveratrol, THP, and resveratrone, to elucidate the singlet oxygen generation following the precursor's excitation. We evaluated the singlet oxygen production using three key indicators: i) absorption band overlap between the derivative and the precursor (a significant overlap is expected in photodynamic therapy to enable secondary excitations); ii)