Supramolecular Encapsulation of Vitamin B6 by Macrocyclic Nanocontainer Cucurbit[7]uril

A pharmaceutically and biologically relevant molecule, pyridoxine hydrochloride (vitamin B-6), was encapsulated inside the cavity of a molecular container, cucurbit[7]uril (CB[7]), in aqueous solution. The CB[7] based "nanocapsule" of vitamin B-6 has been investigated for the first time, via H-1 NMR and UV-visible spectroscopic titrations (including Job's plot) and ab initio molecular modeling. The results have demonstrated that vitamin B-6 forms stable host-guest complexes within CB[7] in 1 : 1 stoichiometry, with a binding affinity of (4.0 +/- 0.5) x 10(3) M-1. Such a nanocapsule could potentially find application in vitamin B-6 formulation for the purpose of enhancing the stability, absorption, and delivery of this important vitamin.