Inclusion complexes of azadirachtin with native and methylated cyclodextrins: solubilization and binding ability

The inclusion complexation behavior of azadirachtin with several cyclodextrins and their methylated derivatives has been investigated in both solution and the solid state by means of XRD, TG–DTA, DSC, NMR, and UV–vis spectroscopy. The results show that the water solubility of azadirachtin was obviously increased after resulting inclusion complex with cyclodextrins. Typically, β-cyclodextrin (β-CD), dimethyl-β-cyclodextrin (DMβCD), permethyl-β-cyclodextrin (TMβCD), and hydroxypropyl-β-cyclodextrin (HPβCD) are found to be able to solubilize azadirachtin to high levels up to 2.7, 1.3, 3.5, and 1.6 mg/mL (calculated as azadirachtin), respectively. This satisfactory water solubility and high thermal stability of the cyclodextrin–azadirachtin complexes, will be potentially useful for their application as herbal medicine or healthcare products.

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