Complexation of NADH analogues with β-cyclodextrin: inhibitory effects of β-cyclodextrin against hydration and copper(II) and hexacyanoferrate(3–) oxidation of 1,4-dihydronicotinamides

Abstract

Fluorescent properties and reaction kinetics of the coenzyme NADH analogues 1 (Y),3(X)-disubstituted-1,4-dihydropyridines (Y = benzyl or para-substituted phenyl; X = CONH₂, CSNH₂, CO₂Me, Ac) have been investigated in the presence of β-cyclodextrin (β-CD). From fluorescence measurements, it is concluded that the NADH analogues form 1:1 inclusion complexes with β-CD. The association constant varies sensitively with the nature of the substituents. The proton-catalysed hydration, copper(II) and hexacyanoferrate(3–) ion oxidation reactions of the NADH analogues are retarded by the presence of β-CD. The protective effects of β-CD against the reactions of NADH analogues are attributed to the inaccessibility of the reacting ions to the NADH analogue molecules included in the β-CD cavity, and destabilization of the reaction intermediates or transition states of the rate-determining steps.