Structural determinants of oxygenated benzalkonium-like disinfectants as human and rat 5α-reductase 1 inhibitors: Integrated SPR binding analysis with docking

The widespread use of oxygenated benzalkonium-like quaternary ammonium disinfectants since COVID-19 raises concerns about their off-target effects on neurosteroidogenesis, particularly via inhibition of 5α-reductase type 1 (5α-R1), a key enzyme in neuroactive steroid synthesis. Here, we evaluated seven such compounds, identifying miramistin, methylbenzethonium, and benzethonium as potent inhibitors of human 5α-R1 (IC 50 = 4.28, 5.01, and 8.80 µM, respectively), with species-dependent potency (human > rat). Mechanistic studies revealed mixed/noncompetitive inhibition, driven by binding to the NADPH site, as confirmed by surface plasmon resonance (SPR) and enzyme kinetics as well as in silico docking. Molecular docking elucidated interactions with key residues (e.g., Asn198 in human vs. Tyr199 in rat), rationalizing the observed interspecies differences, particularly for miramistin. Despite high microsomal activity, limited cell permeability diminished efficacy in intact cells, suggesting a need for cellular assay. These findings advance mechanistic understanding of 5α-R1 inhibition by these disinfectants and highlight their broader implications for potential disruption of neurosteroid pathways in humans as endocrine disruptors, regulatory risks due to species-specific pharmacodynamics, and opportunities to identify safer quaternary ammonium compounds without affecting neurosteroids. The study underscores the necessity of interspecies validation in assessments of environmental chemicals targeting steroidogenic enzymes. QACs’ potent 5α-R1 inhibition risks endocrine disruption in rodents and humans. High logP suggests bioaccumulation potential, demanding environmental fate studies. • Miramistin inhibits human 5α-R1 (IC 50 =4.28 µM), 7.2 × stronger than rat. • SPR confirms NADPH site binding for mixed inhibition of miramistin. • Network pharmacology identifies QACs related to AD with neurosteroids. • Human 5α-R1 is more sensitive to the inhibition by miramistin than rat one.