Triplet state characteristics and singlet oxygen generation properties of anthracyclines

• Published in: Biochimica et biophysica acta Vol. 990; no. 2; pp. 190 - 197
• Main Authors: Andreoni, Alessandra, Land, Edward J., Malatesta, Vincenzo, McLean, Andrew J., Truscott, T. George
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.02.1989; Elsevier; North-Holland
• Subjects: Acetamides; Anthracycline; Antibiotics, Antineoplastic; Biological and medical sciences; Chemical Phenomena; Chemistry, Physical; Daunorubicin; Doxorubicin; ESR; Flash photolysis; Fluoroacetates; Fundamental and applied biological sciences. Psychology; Mathematics; Miscellaneous; Molecular biophysics; Naphthacenes; Photolysis; Pulse Radiolysis; Radiation-biomolecule interaction; Singlet oxygen; Triplet state; PR; Ad; D; ESR; DAc; DMPO; 5-ID; CAPcS; Triplet state; Singlet oxygen; Anthracycline; LFP; ISC; Flash photolysis; TMP-one; Dc; Antineoplastic agent; Photosensitization; Anthracyclins; Laser photolysis; Pulse radiolysis
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/S0304-4165(89)80033-9

The triplet states of adriamycin (Ad), daunomycin (D) and two daunomycin analogues, daunomycinone (Dc) and daunomycin N-trifluoroacetamide (DAc), have been studied using laser flash photolysis and pulse radiolysis techniques. Triplet lifetimes, molar absorption coefficients, energy levels and quantum yields have been obtained for Dc and DAc, and estimated for D and Ad. Time-resolved near-infrared singlet oxygen luminescence measurements have been carried out on D, Ad and 5-iminodaunomycin (5-ID) in 2H 2O solution and Dc in benzene solution at room temperature. Singlet oxygen quenching by the water-soluble anthracyclines was observed and a second-order rate constant of approx. 10 8 M −1 · s −1 obtained. Electron spin resonance experiments have demonstrated that D photoexcited at λ < 365 nm gives rise to singlet oxygen as shown by its reaction with 2,2,6,6-tetramethyl-4-piperidone to give the corresponding nitroxyl radical. Although all the anthracyclines studied have the ability to photosensitise the formation of singlet oxygen, the quantum yields are very low (φΔ ≈ 0.02–0.03), suggesting that these anthracyclines would be poor photodynamic sensitisers.