Objective: The aim of this study was to compare production of nanocrystals of a poorly water-soluble antioxidant, quercetin, by top-down and bottom-up techniques. The top-down method used was high pressure homogenization (HPH) and bottom-up method of evaporative precipitation of nanosuspension (EPN) was used and the products from these methods were compared.
Methods: Quercetin nanosuspensions were produced via HPH using Micron Lab40 by applying 20 homogenization cycles at 1500 bar. The nanosuspensions contained 2 to 10 % (w/w) of quercetin and 0.5 to 2.5 % (w/w) of Tween 80 as stabilizer. For EPN method, quercetin powder was dissolved in a good solvent (ethanol) and then nanocrystals were formed by quickly adding an antisolvent (hexane). Drug crystals in the nanosuspension were obtained by quick evaporation of the solvent and antisolvent. Drug concentration of 5-15 mg/ml and solvent to antisolvent ratio of 1:10 to 1:25 (by volume) were used.
Results: The particle size of the commercial drug was about 34 µm. The smallest average particle size obtained after HPH was 483 nm, and after EPN it was 739 nm. The dissolution rate of the quercetin nanocrystals enhanced manifolds compared to the commercial quercetin. The antioxidant activities of the quercetin nanocrystals were better than the commercial drug.
Conclusions: This study demonstrated that both the methods can successfully prepare quercetin nanocrystals. HPH produced smaller crystals, which presented slightly better dissolution than those produced by the EPN. However, EPN is a simple process compared to the energy intensive HPH and is cost effective.