Investigating hesperetin nanocrystals with tailor-made sizes for the prevention and treatment of Alzheimer's disease.

Poor aqueous solubility of drug substances is associated with poor bioavailability and thus hampers the effective use of many potent active pharmaceutical ingredients. Various strategies to overcome poor solubility are available, whereby drug nanocrystals represent one of the most powerful formulation strategies to enhance the kinetic solubility and dissolution rate of poorly soluble drugs. Nanocrystals are simply obtained by milling large-sized drug powders to sizes < 1 µm. The so obtained nanocrystals possess an increased dissolution rate and kinetic solubility when compared with larger-sized bulk material. The aim of this study was to produce differently sized hesperetin nanocrystals and to investigate the influence of nanocrystal size on the bioefficacy of the natural antioxidant hesperetin in two cell culture models for the prevention and treatment of Alzheimer's disease. Results showed that the testing of poorly soluble compounds is challenging and requires incredibly careful characterization. Reasons for this are possible changes of the formulations in cell culture media which can occur due to various reasons. If the changes are not considered, results obtained can be misleading and even lead to a false interpretation of the results obtained. Besides, results demonstrate the increase in dissolution rate with decreasing particle size that is especially pronounced with particle sizes < 200 nm. Data also provide clear evidence that smaller nanocrystals with higher kinetic solubility possess higher antioxidant capacity. This results in lower amounts of free radicals in the cell culture models, suggesting that hesperetin nanocrystals, that improve the poor aqueous solubility of hesperetin, are promising for the prevention and treatment of Alzheimer's disease.