Hidehiro BEPPU

Coenzyme Q10 (CoQ10) is a well-known antioxidant agent that has low solubility in water and poor absorption in humans. CoQ10-cyclodextrin (CD) complex powders containing 20-24% (w/w) CoQ10 were prepared to investigate the effects of different CDs on three properties of CoQ10: aqueous solubility, heat of fusion, and absorption in humans. The aqueous solubility of CoQ10 was increased by α-CD and dextrin, while β-CD, γ-CD and β-Iso^® formed an insoluble complex with CoQ10. β-CD, γ-CD and β-Iso^® improved the thermal property of CoQ10, as determined by differential scanning calorimetry. That is, β-CD, γ-CD and β-Iso^® most likely formed complexes with CoQ10, as the CoQ10 endothermic peak obtained by differential scanning calorimetry greatly decreased in the presence of these compounds. For the absorption studies, 20 healthy female volunteers were divided randomly into four groups and orally administered either CoQ10, the CoQ10-β-CD complex, CoQ10-γ-CD complex or CoQ10-β-Iso^® complex containing 0.30 g CoQ10 under fasting conditions. The concentration of CoQ10 in plasma before and 2, 4, 6, 8 and 24 h after sample administration was measured by HPLC analysis, and the plasma concentration of exogenous CoQ10 was calculated as the plasma concentration of CoQ10 before administration subtracted from the value after administration. The area under the plasma exogenous CoQ10 concentration/time-course curve from 0 to 8 h of the three complex groups was significantly higher than that of the CoQ10 group, indicating that β-CD, γ-CD and β-Iso^® accelerate the absorption of CoQ10 in humans.