Glucosamine hydrochloride inhibits malondialdehyde formation by lipoprotein oxidation. Lipoproteins (0.5 mg/ml) were incubated at 30°C in phosphate-buffered saline for 4 hours in the absence or presence of 5 μM Cu2+ or 5 μM Cu2+ and 50, 5, or 0.5 mM glucosamine hydrochloride. Data are expressed as malondialdehyde equivalents in nanomoles and are presented as the mean of a duplicate set of samples ± standard error. A representative of two experiments is shown. Cu, copper; Glu, glucosamine hydrochloride; LDL, low-density lipoprotein.