Highly efficient complexation of sanguinarine alkaloid by carboxylatopillar[6]arene: pKa shift, increased solubility and enhanced antibacterial activity

Encapsulation of a physiologically active substance, sanguinarine (SA), by a water soluble carboxylatopillar[6] arene (CP6A), is described. The efficient complexation by CP6A, giving a K-a value of (2.4 +/- 0.3) x 105 M-1 in pH 7.4, served to increase the water solubility by 4.3-fold, cause a 2.02 shift in pK(a), and enhance the antibacterial activity of SA.