The reversible hydration of the malaria pigment β-hematin

Abstract

β-Hematin, the crystalline heme detoxification product of red blood cell digestion by the malaria parasite, can reversibly absorb up to 14% of its mass in water. Heating hydrated β-hematin to temperatures greater than 150 °C results in loss of the hydrated water, which is readily reabsorbed on standing in air at room temperature. The amount of water absorbed is source dependent with highly crystalline samples produced by the anhydrous-base-mediated dehydrohalogenation being twice as absorptive as more amorphous samples produced by the aqueous acid precipitation method. Infrared spectroscopy and thermal gravimetric analysis have been used to measure the amount of water lost and gained during these experiments. X-ray powder diffraction has been used to characterize the effect of hydration state on the lattice parameters. Taken together these experiments resolve literature discrepancies concerning the elemental composition of synthetic and extracted natural β-hematin.Key words: malaria pigment, hemozoin, β-hematin, hydration, thermal gravimetric analysis, powder diffraction.