Complexations of β-cyclodextrins with naringenin, naringin and catechin: thermodynamic parameters and regulation of mitochondrial functions in vitro

Abstract

ABSTRACT Flavonoids are exogenous phytochemicals with high antioxidative potential. The present work provides the mechanism of the complexations of low water-soluble flavanone naringenin, its glycosylated form naringin, and water-soluble flavan-3-ol catechin with β-cyclodextrin (βCD) and hydroxypropyl-β-cyclodextrin (HPβCD). The flavonoids studied showed high affinity in the interactions with HPβCD (the association constants K and the stoichiometry N were equal to 8500 ± 950 М−1 and 0.85 ± 0.05, 9400 ± 1200 М−1 and 1.7 ± 0.10, 7550 ± 600 M−1 and 1.25 ± 0.05 in the case of naringenin, naringin and catechin, respectively). The formations of the complexes with β-cyclodextrins markedly increased the water solubility of naringenin and naringin. The flavonoid–HPβСD complexations were exothermic (ΔH ˂ 0) and spontaneous (ΔG ˂ 0). The naringenin and naringin complexations with HPβCD were entropy-driven, and the catechin complexation was enthalpy-driven. Flavonoid molecules dispersed in the HPβCD structure during complexations. The flavonoid–HPβCD associations demonstrated enthalpy–entropy compensation. Naringenin (5–50 μM) and, to a lesser extent, catechin inhibited the respiration of isolated rat liver mitochondria. Naringenin, naringin and catechin (5–25 μM) increased the rate of Ca2+-induced mitochondrial permeability transition. The complexations with HPβCD did not significantly influence the effects of the flavonoids on respiration and enhanced the effects on mitochondrial permeability transition.