Release of reactive selenium species from phthalic selenoanhydride in the presence of hydrogen sulfide and glutathione with implications for cancer research

Abstract

The last decade has witnessed a renewed interest in selenium (Se) as an element able to prevent a range of illnesses in humans, mainly through supplementation. However, such supplementation relies on species such as sodium selenite or selenomethionine, which proved to have limited solubility and bioavailability, thus leading to limited activity. To overcome this limitation, other selenium species need to be explored, such as phthalic selenoanhydride (R-Se), which is soluble in physiological media. R-Se releases various reactive selenium species (RSeS), including hydrogen selenide (H₂Se), that can interact with cellular components, such as glutathione (GSH) and hydrogen sulfide (H₂S). This interplay between R-Se and the cellular components provides a sophisticated biochemical release mechanism that could be behind the noteworthy biological activities observed for this compound. In order to investigate the interactions of phthalic chalcogen anhydrides with H₂S or GSH, we have employed UV-vis spectrophotometry, electron paramagnetic resonance spectroscopy (EPR) and plasmid DNA (pDNA) cleavage assay. We found that apart from R-Se, the other analogues do not have the ability to scavenge the ˙cPTIO radical or to cleave pDNA on their own. In contrast, the scavenging potency for the ˙cPTIO radical and for the O₂˙⁻ radical exerted by R-Se and its sulfur analogue (R-S) significantly increased when they were evaluated in the presence of H₂S. However, GSH only changed the radical scavenging activity of R-Se. These new discoveries may explain some of the biological activities associated with this class of compounds and open a new approach to ascertain the possible mechanisms underlying their biological actions.