biostudies-literatureUnknown9(10)Hevia DThe indolamine melatonin (MEL) is described as an antioxidant and a free radical scavenger. However occasionally, the indoleamine has been reported to increase free radicals with insufficient mechanistic explanation. In an attempt to find a reason for those controversial results, a potential mechanism that explains MEL prooxidant activity is investigated. The current controversy about redox detection methods has prompted us to search a possible interaction between MEL and dichlorodihydrofluorescein (DCFH2), perhaps the most widely fluorescence probe employed for free radicals detection in cellular models. Here, it is demonstrated that melatonin potentiates the photooxidation of DCFH2 in a cell-free system, increasing the production of its fluorescent metabolite. Indeed, MEL works as an antPloS onee109257https://www.ebi.ac.uk/biostudies/studies/S-EPMC4183549biostudies-literatureMelatonin enhances photo-oxidation of 2',7'-dichlorodihydrofluorescein by an antioxidant reaction that renders N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK).PMC4183549Rodriguez-Garcia ATan DXSainz RMMayo JCHevia DfalseMelatonin enhances photo-oxidation of 2',7'-dichlorodihydrofluorescein by an antioxidant reaction that renders N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK).The indolamine melatonin (MEL) is described as an antioxidant and a free radical scavenger. However occasionally, the indoleamine has been reported to increase free radicals with insufficient mechanistic explanation. In an attempt to find a reason for those controversial results, a potential mechanism that explains MEL prooxidant activity is investigated. The current controversy about redox detection methods has prompted us to search a possible interaction between MEL and dichlorodihydrofluorescein (DCFH2), perhaps the most widely fluorescence probe employed for free radicals detection in cellular models. Here, it is demonstrated that melatonin potentiates the photooxidation of DCFH2 in a cell-free system, increasing the production of its fluorescent metabolite. Indeed, MEL works as an ant2014-01-01T00:00:00Z20142025-05-29T16:00:42.094Z2025-05-29T16:00:42.094ZS-EPMC41835492527538010.1371/journal.pone.0109257