Photochemistry of Common Xanthene Fluorescent Dyes as Efficient Visible-light Activatable CO-Releasing Molecules

Abstract

Xanthene derivatives are organic dyes, some of which are routinely used in different chemical and biological applications, including human medicine. In this work, we investigated the photochemistry of some of the most common ones, fluorescein, eosin Y, and rose bengal, and major products of their photodegradation using optical spectroscopy, NMR, chromatography and mass spectroscopy techniques. These substances, usually considered (photo)chemically stable, were found to liberate carbon monoxide (CO) in 40–80% chemical yields upon extensive irradiation with visible light in aqueous solutions during their multistep concomitant degradation processes. In addition, a number of low-mass secondary photoproducts, such as phthalic and formic acids, were identified in the irradiated mixtures. We demonstrate that these common fluorescent dyes can also be considered as visible-light activatable carbon monoxide (CO)-releasing molecules (photoCORMs) under specific conditions with potential biological implications.

Antiproliferative and Cytotoxic Activities of Fluorescein—A Diagnostic Angiography Dye

“…As we do not know the exact mechanism of fluorescein photodegradation, other as yet unidentified photoproducts might contribute to the observed biological effects. In fact, we recently described the production of phthalic and formic acids upon fluorescein irradiation [37], which supports this assumption. Moreover, we could not clearly distinguish between the individual contributions of 1 O 2 and CO on cellular toxicity and metabolism, as their effects might overlap.…”

“…In this paper, we focus on the findings that irradiation of fluorescein in aqueous solutions produces not only 1 O 2 but also CO, as also demonstrated in our parallel article describing the photochemical behavior of common xanthene dyes [37]. Due to the increasing mass of evidence indicating the possible biological activities of both 1 O 2 and CO, our goal was to evaluate the biological consequences of fluorescein photochemistry using an in vitro hepatic cell model, specifically its toxicity, as well as its effects on both cellular metabolism and the cell cycle.…”