Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Inclusion complexation of an antimicrobial quaternary ammonium salt, carbethopendecinium bromide (SBr, Septonex), with five cyclodextrins was investigated potentiometrically using the prepared membrane electrodes selective to the surface-active carbethopendecinium cations (S⁺). Relatively strong complexation of the S⁺ cations with native α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and their random-substituted derivatives, namely hydroxypropyl-α-cyclodextrin (HP-α-CD), methyl-β-cyclodextrin (M-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD), was evidenced in dilute aqueous solution. In the region where the potentiometrically determined concentration of the free S⁺ cations remained lower than the critical micelle concentration (cmc) of SBr by a factor of ca ten, formation of the 1:1 complexes with the complexation constants K₁₁ ≈ 10⁴-10⁵ was evaluated by two respective methods, based on a modified linear and a non-linear regression. Deviations from the 1:1 complexation were observed when concentration of the free S⁺ cations approached cmc of SBr more closely and also in solutions with large excess of α-CD. Comparison of K₁₁ values corroborated the inclusion of the n-C₁₄H₂₉ alkyl chain of the carbethopendecinium cation as the mechanism of its complexation with cyclodextrins. The well-soluble native α-CD with good complex-forming capability towards S⁺ cations may be especially suitable for possible blocking the undesirable residues of carbethopendecinium bromide.

Keywords: Quaternary ammonium salt; Cationic surfactant; Antimicrobial activity; Septonex; α-Cyclodextrins; β-Cyclodextrins; Inclusion complexes; Potentiometry; Membrane electrodes.

References: 27 live references.