Usenik, Andrea; Pičuljan, Katarina; Kukina Gradečak, Karla; Katovčić, Stella; Talajić, Gregor; Šekutor, Marina; Požar, Josip (2026) Molecular recognition of steroid isomers by cyclodextrins and cucurbiturils: thermodynamic contributions and structural determinants. New Journal of Chemistry, 50 (32). pp. 13451-13462. ISSN 1144-0546
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Abstract
Binding of cis- and trans-steroids with cyclodextrins (CDs) and cucurbiturils (CBs) comprised of seven and eight monomeric subunits was investigated to clarify the effects of gonane isomerism and functionalisation on binding stoichiometry and thermodynamic complexation parameters (K°, ΔrX° where X = G, H, S, Cp). While trans-steroids formed both 1 : 1 and 1 : 2 (guest : host) complexes with β-cyclodextrin, the binding of V-shaped cis-androsterone resulted solely in the formation of a 1 : 1 complex, revealing that steroid isomerism dictates the binding stoichiometry with this receptor. By contrast, all guests formed exclusively 1 : 1 complexes with CB7, CB8, and γ-CD, whereby the former receptor showed pronounced selectivity for the trans-steroids combined with negligible affinity for the cis-isomer. Complexation with hosts containing seven monomeric units and with CB8 was predominantly enthalpically driven, while the favourable entropic term dominated over the enthalpic one in the case of γ-cyclodextrin. Due to steric compatibility, and enthalpically unfavourable hydration of its cavity, the larger cucurbituril outperformed all other studied hosts. A clear correlation between the cyclodextrin affinity for the bile salt anions and the number of OH groups attached to the gonane backbone was observed. In accord, the ROESY NMR spectra of the complexes revealed that this polar group prefers to remain hydrated rather than to engage in interactions with the hosts, in turn shifting the guest binding site from rings A and B towards the non-polar side chain and the ring D. The obtained results demonstrate how the steroid isomerism and functionalisation, as well as cyclodextrin and cucurbituril size determine the inclusion complex stoichiometry and its stability, providing a basis for the rational use of these receptors in recognition, solubilisation, and separation of steroids and their derivatives.
| Item Type: | Article | ||||||||||||||||
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| Uncontrolled Keywords: | steroids; bile salts; cyclodextrins; thermodynamics; calorimetry; hydrophobic effect | ||||||||||||||||
| Subjects: | NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry |
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| Divisions: | Division of Organic Chemistry and Biochemistry | ||||||||||||||||
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| Depositing User: | Lorena Palameta | ||||||||||||||||
| Date Deposited: | 19 Aug 2026 10:50 | ||||||||||||||||
| URI: | https://fulir.irb.hr:/id/eprint/12121 | ||||||||||||||||
| DOI: | 10.1039/d6nj02208a |
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