Enhancement of Oral Bioavailability of Functional Ingredients by Complexation with Cyclodextrin

Natural lipophilic bioactives that possess human health benefits, such as coenzyme Q10 (CoQ10) and R-α-lipoic acid (RALA), often have undesirable characteristics that limit their use as nutraceuticals and cosmeceuticals. These bioactives are usually unstable against oxygen, ultraviolet light, low pH and heat. Furthermore, their watersolubility is low because of their hydrophobic nature or instability and this leads to low bioavailability. Therefore, systematic studies have been performed to investigate improvements in the stability, water-solubility and bioavailability of lipophilic bioactives through complexation with cyclodextrins (CDs). The solubility of CoQ10 in water is extremely low, resulting in low bioavailability when administered orally. Bioavailability of CoQ10 was enhanced significantly by complexation with γ-CD. CoQ10 generally agglutinates, but the dissociated CoQ10 from γ-CD was captured by bile acid to form micelles without aggregation and therefore both solubility and bioavailability were enhanced. RALA is available as a functional food ingredient but is unstable to heat or acid. To stabilize RALA, complexation with γ-CD was investigated. RALA was unstable molecule, whereas RALA-γCD complex was stable under the acidic conditions of the stomach and was easily absorbed in the intestine. CD complexation is a promising technology as a formulation aid for oral delivery of insoluble or unstable ingredients such as CoQ10 and RALA.