Effects of Blue-Light-Induced Free Radical Formation from Catechin Hydrate on the Inactivation of Acinetobacter baumannii, Including a Carbapenem-Resistant Strain

Abstract

Catechin is a flavan-3-ol, a derivative of flavans, with four phenolic hydroxyl groups, which exhibits a wide range of physiological properties. Chromatographic analyses were employed to examine the effects of blue light irradiation on the changes of catechin hydrate in an alkaline condition. In particular, the detection of a superoxide anion radical (O2•−), a reactive oxygen species (ROS), and the inactivation of Acinetobacter baumannii (A. baumannii)—including a carbapenem-resistant A. baumannii (CRAB)—was investigated during the photoreaction of catechin hydrate. Following basification with blue light irradiation, the transparent solution of catechin hydrate turned yellowish, and a chromogenic catechin dimer was separated and identified as a proanthocyanidin. Adding ascorbic acid during the photolytic treatment of catechin hydrate decreased the dimer formation, suggesting that ascorbic acid can suppress the photosensitive oxidation of catechin. When catechin hydrate was irradiated by blue light in an alkaline solution, O2•− was produced via photosensitized oxidation, enhancing the inactivation of A. baumannii and CRAB. The present findings on the photon-induced oxidation of catechin hydrate provides a safe practice for the inactivation of environmental microorganisms.

Enhancement of Phthalocyanine Mediated Photodynamic Therapy by Catechin on Lung Cancer Cells

“…As reported by previous works in our lab, increased oxidative stress by plant extracts and phytochemicals reduced the intracellular ATP levels [22]. Yang et al reported that light-activated CA caused increased DNA strand breakage resulting in the depletion of cellular NAD + and ATP levels leading to cell death [23]. The nuclear damage observed in A549 cells by CA and PDT through Hoechst staining is in correlation with the observed morphological changes in the treated cells revealing cytotoxicity and cell death.…”

Effects of 462 nm Light-Emitting Diode on the Inactivation of Escherichia coli and a Multidrug-Resistant by Tetracycline Photoreaction

“…Liang et al reported that riboflavin or FMN treated with blue light illumination produced a large amount of O 2 • − that degraded crystal violet [ 14 ] and led to the inactivation of E. coli and MRSA through ROS formation [ 3 , 13 , 30 ]. It has been reported that catechin hydrates under blue light illumination, and O 2 • − was generated from photo-oxidation, increasing the inactivation rate of A. baumannii , including the carbapenem-resistant, A. baumannii [ 12 , 50 ]. The O 2 • − generation in cells may induce DNA degradation, membrane peroxidation, and the destruction of endothelial cells [ 51 ].…”

“…Both direct and indirect methods can be utilized to detect active O 2 • − . The direct method requires particular apparatus, such as an electron spin resonance (ESR) spectroscopy, while the indirect ways are easily exercised in analysis [ 12 ]. The nitro blue tetrazolium (NBT) reduction method is an indirect assay for determining O 2 • − , and NBT can be reduced by the O 2 • − from intermediates [ 32 ].…”

“…Reactive oxygen species (ROS), including hydrogen peroxide (H 2 O 2 ), the hydroxyl radical (•OH), the peroxyl radical (ROO•), and the superoxide anion radical (O 2 • − ), are generally reactive molecules or radical species [ 12 ]. It has been reported that riboflavin treated with blue light illumination can be applied to inactivate E. coli , S. aureus , and methicillin-resistant S. aureus (MRSA) by DNA cleavages, caused by O 2 • − generation [ 3 , 13 , 14 ].…”

Introduction to “Advances in Photodynamic Therapy 2018”

“…The next paper [3] comes from the laboratories of Iou-Zen Chen and Ji-Yuan Liang in Taiwan. These authors studied a flavan-3-ol called catechin as a blue-light activated photosensitizer to kill Gram-negative bacteria Acinetobacter baumannii and a carbapenam-resistant variant.…”