Inclusion of the Phytoalexin trans -Resveratrol in Native Cyclodextrins: A Thermal, Spectroscopic, and X-Ray Structural Study

• Published in: Molecules (Basel, Switzerland) Switzerland), 2020-02, Vol.25 (4), p.998
• Main Authors: Catenacci, Laura, Sorrenti, Milena, Bonferoni, Maria Cristina, Hunt, Lee, Caira, Mino R
• Format: Article
• Language: English
• Subjects: Amorphization; Antioxidants; Bioavailability; Calorimetry; Complex formation; Complexation; Crystallography, X-Ray; Crystals; Cyclodextrin; Cyclodextrins; Cyclodextrins - chemistry; Differential scanning calorimetry; Evaporation; Fourier analysis; Fourier transforms; Humans; inclusion complexes; Infrared analysis; Infrared spectroscopy; Irradiation; Methods; Microwaves; NMR; Nuclear magnetic resonance; Pharmaceuticals; Phytoalexins; Resveratrol; Resveratrol - chemistry; Sesquiterpenes - chemistry; Single crystals; Spectrum analysis; Stereoisomerism; thermal analysis; Thermodynamics; Thermogravimetric analysis; trans-resveratrol; X ray analysis; X ray powder diffraction; X-Ray Diffraction; x-ray structure
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules25040998

The aim of the study was to determine the feasibility of complexation between the antioxidant -resveratrol (RSV) and underivatized cyclodextrins (CDs) using a variety of preparative methods, including physical mixing, kneading, microwave irradiation, co-evaporation, and co-precipitation techniques. Products were characterized using differential scanning calorimetry (DSC), simultaneous thermogravimetric/DSC analysis (TGA/DSC), Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (PXRD). With α-CD and RSV, sample amorphization was revealed by PXRD and FT-IR, but no definitive inclusion complexation was evident. Similar results were obtained in attempts to complex RSV with β-CD. However, complex formation between γ-CD and RSV was evident from observation of an endo-/exothermic effect appearing in the DSC trace of the product from kneading and was further corroborated by FT-IR and PXRD methods. The latter technique indicated complexation unequivocally as the diffraction peak profile for the product matched that for known isostructural γ-CD complexes. Single crystal X-ray analysis followed, confirming the predicted complex between γ-CD and RSV. A combination of H NMR and TGA data yielded the complex formula (γ-CD) ·(RSV) ·(H O) . However, severe disorder of the RSV molecules prevented their modeling. In contrast, our previous studies of the inclusion of RSV in methylated CDs yielded crystals with only minor guest disorder.