Quenching of singlet oxygen by natural and synthetic antioxidants and assessment of electronic UV/Visible absorption spectra for alleviating or enhancing the efficacy of photodynamic therapy

Abstract

Abstract-Photodynamic therapy (PDT) is one of the methods involved in cancer treatment exploiting singlet oxygen as a weapon to kill cancer cells. Singlet oxygen, a bizarre reactive oxygen species as it is not related to electron transfer to O 2 but it is one of the most active intermediate involved in biochemical reactions as it directly reacts with all the major macromolecules like DNA, protein, lipids etc, various photosensitized oxidations and in the photodegradation of dyes and polymers. Recent studies about the usage of antioxidant along with the photo-sensitizer involved in photodynamic therapy have shown concentration-dependent dual behavior like usually it retards the efficacy of PDT but at a higher dose , it actually enhances the damaging effect of PDT. The natural and synthetic antioxidants are being used in our day to day life in order to increase the shelf life of various food ingredients and processed foods. In this paper, we have compared natural and synthetic antioxidants along with the known singlet oxygen quencher (DABCO) in order to understand the quenching potential of singlet oxygen ( 1 O 2 ) which is lowest electronically excited state of molecular oxygen. The singlet oxygen can be artificially generated through various methods such as sunlight, phosphate, ozonides, NaOCl & H 2 O 2 etc. We have studied the mechanisms of selected antioxidants on the bleaching of RNO linked with the energy decay of 1 O 2 produced by the Mallet reaction (H 2 O 2 + HOCl → HCl + H 2 O + 1 O 2 ). β-Carotene, α-Tocopherol, Ascorbic acid and Quercetin exhibited best dosedependent singlet quenching ranging from 92.3 to 56.5 % at 100μM among others. Overall singlet oxygen is a major concern of light-related properties so we have analyzed the theoretical aspect of electronic UV/visible absorption spectra of the antioxidants studied through ZINDO CI semi-empirical Hamiltonian method. We have compared only the first singlet state of molecules in order to understand whether the structure of the molecules has any influence on the quenching potential. Considering the main features associated with singlet states, we have seen a drastic correlation between known sensitizer of singlet oxygen, i.e. Rose Bengal and DABCO, known scavenger of singlet oxygen in terms of energy and wavelength. This study is important as it highlights the behavior of antioxidant which can improve the effects of photosensitizer used in photodynamic therapy.

Exploring the Applications of the Photoprotective Properties of Anthocyanins in Biological Systems

“…However, depending on the concentration of antioxidants, the hormesis effect may promote a pro-oxidative behavior. A recent study showed that several natural and synthetic antioxidants have the potential to enhance the efficacy of PDT, probably due to the quenching action driving the mechanism of PDT towards free radical rather than 1 O 2 [ 184 ]. Anthocyanins are reported as singlet oxygen quenchers.…”

Antioxidant properties of water-soluble phthalocyanines containing quinoline5-sulfonic acid groups

“…Some antioxidant molecules are reported to increase the photodamaging effect of photosensitizers used in PDT with many kinds of sensitizers [3].…”

Co2SnO4@Co3O4-SnO2 composite for enhanced peroxymonosulfate activation: Catalytic degradation of diclofenac, mechanism and degradation pathways

“…•− and Imidazole was reported to be a scavenger of singlet oxygen 1 O 2 (Fatima et al 2016). As shown inFig.9, the degradation rate of DCF was 8% with the addition of Imidazole (75mM) and no inhibitory effect was observed when EtOH (2mM), AA(2mM), or TBA (0.05 M) agents were introduced into the reaction system.…”