After-Rinsing Hair Growth Promotion of Minoxidil-containing Amino ${\alpha}$-Cyclodextrins

Triamino ${\alpha}$-cyclodextrin (CD) was synthesized and the inclusion complex with Minoxidil (MXD) was prepared. ${\alpha}$-CD was azidated by modifying the 6-hydroxylmethyl CD rim with sodium azide. Then, mono-, di-, tri-, and tetra-azidocyclodextrins were separated by a flash column chromatography and reduced to the corresponding amines by hydrogenation with Pd/C. The substantivities of MXD included in either 2-hydroxypropyl ${\alpha}$-CD (HP ${\alpha}$-CD) or triamino ${\alpha}$-CD were evaluated in vitro using hairless mice skins. After applying the preparations onto the skin and rinsing it, the amount of the drug left on the skin was determined using high-performance liquid chromatography (HPLC). It was the highest when the drug was included in triamino ${\alpha}$-CD. The electrostatic interaction between the protonated amino CD and the negatively charged skin would be responsible for the relatively high substantivity. The in vivo hair growth promotion effect of each preparation was investigated, where the sample application onto the clipped backs of female mice (C57BL6) and the subsequent rinsing of the backs were done once a day for 30 days. Only MXD in triamino ${\alpha}$-CD had hair growth promotion effect, possibly due to the significant substantivity.