Although unexpected, our findings align with infrequent reports in the existing literature. For example, dopamine derivatives -including dopamine methacrylamide-polyacrylamide hydrogels, dopamine methacrylamide monomer, and free dopamine (7-21 mM) -were shown to autoxidize over 48 hours in DMEM supplemented with 10% FBS . However, that study monitored autoxidation with a hydrogen peroxide assay (instead of spectrophotometric browning detection), and examined reactions over hours-long time frames (rather than our 10minute interval assays). Another study demonstrated autopolymerization of catecholamine precursors (5 mM L-DOPA, methyl-L-DOPA, epinephrine, or norepinephrine) while mechanically stirring at room temperature for 72 hours in Tris buffer at pH 7.4 over 72 hours ). Yet, that study did not report any spectral changes or intermediate timepoint observations within the 72-hour incubation. While these studies differ from ours in experimental design, they underscore the potential enzyme-and cell-free catechol reactivity under physiological conditions. Taken together, the pharmacokinetic implications are profound: catechol transformation products may undergo rapid formation both in vitro (within unsupplemented or supplemented culture media) and in vivo (during gastrointestinal transit and intestinal absorption), potentially preceding cellular uptake and interaction with biological targets.