Quercetin, a fluorescent bioflavanoid, inhibits Trypanosoma brucei hexokinase 1

► The trypanocidial bioflavanoid quercetin (QCN) is a potent mixed inhibitor of Trypanosoma brucei hexokinase 1 (TbHK1) (IC50 = 4.1 ± 0.8 μM). ► QCN binds close to the enzyme active site and influences fluorescence of the single tryptophan residue, much like ATP does. ► In live parasites, QCN localizes in part to glycosomes, the subcellular organelle that houses TbHK1. ► T. brucei that over-express TbHK1 are more resistant to QCN, while cells with reduced TbHK1 are more sensitive, suggesting that TbHK1 is a target of the compound.