Inclusion of the allicin mimic S-p-tolyl t-butylthiosulphinate in β-cyclodextrin

Abstract

Allicin, the active thiosulphinate present in freshly crushed garlic, has potent antimicrobial activity but is chemically labile. As part of a study aimed at producing stable allicin analogues as potential antimicrobial agents, the allicin mimic S-p-tolyl t-butylthiosulphinate was synthesised and complexed with β-cyclodextrin (β-CD). The inclusion complex, β-CD·S-p-tolyl t-butylthiosulphinate·12.5H₂O, was characterised by thermal analysis techniques (HSM, TG, DSC), powder X-ray diffraction and single-crystal X-ray diffraction. The inclusion complex is dimeric (space group C222₁) with the guest disordered over three positions. Within each β-CD molecule of the dimer, each disordered guest component is located in the host cavity with the t-butyl group protruding slightly from the primary hydroxyl side, while the phenyl ring is situated near the secondary hydroxyl side and the thiosulphinate moiety is centrally located within the host cavity. Stereoselectivity of guest inclusion is implicit in the disordered model, which reflects a 2:1 ratio of S- and R-enantiomers in the β-CD cavity.

Keywords:

• thiosulphinate
• allicin
• cyclodextrin
• X-ray diffraction
• thermal analysis

Acknowledgements

We thank the University of Cape Town and the NRF for financial assistance. This material is based on the work supported by the National Research Foundation under Grant number NRF 67941. Any opinions, findings and conclusions or recommendations expressed in the material are those of the author and do not necessarily reflect the views of the National Research Foundation.