Flavonol-Based Carbon Monoxide Delivery Molecule with Endoplasmic Reticulum, Mitochondria, And Lysosome Localization

Light-triggered carbon monoxide (CO) delivery molecules are of significant current interest for evaluating the role of CO in biology and as potential therapeutics. Herein we report the first example of a metal free CO delivery molecule that can be tracked via confocal microscopy at low micromolar concentrations in cells prior to CO release. The NEt₂-appended extended flavonol (4) localizes to the endoplasmic reticulum, mitochondria, and lysosomes. Subcellular localization of 4 results in CO-induced toxicity effects that are distinct as compared to a nonlocalized analog. Anti-inflammatory effects of 4, as measured by TNF-α suppression, occur at the nanomolar level in the absence of CO release, and are enhanced with visible-light-induced CO release. Overall, the highly trackable nature of 4 enables studies of the biological effects of both a localized flavonol and CO release at low micromolar to nanomolar concentrations.