Effects of branched cyclodextrins on the solubility and stability of terpenes.

In order to investigate the application potential of branched CDs, the solubilizing ability and the stabilizing ability of G2-betaCD and GUG-betaCD were investigated by using twelve terpenes (d-limonene, myrcene, terpinolene, geraniol, l-menthol, nerol, alpha-terpineol, citral, d-citronellal, l-perillaldehyde, (R)-l-carvone, and menthone) as guest compounds. G2-betaCD and GUG-betaCD showed more solubilizing ability for these twelve terpenes than betaCD, and the ability of GUG-betaCD was almost the same as that of G2-betaCD. The stabilizing ability of terpene-GUG-betaCD complexes was different from that of G2-betaCD. GUG-betaCD was superior to G2-betaCD, especially in the solid state. This result may have been caused by the difference in structure of side chain, namely the hydroxymethyl group in G2-betaCD and the carboxyl group in GUG-betaCD.