Dendrimers as Color-Stabilizers of Pyranoanthocyanins: The Dye Concentration Governs the Host-Guest Interaction Mechanisms

• Type: Article in International Scientific Journal
• Date: 2021

Authors

Luis Cruz (Author) FCUP; Correa, J (Author) Other; Nuno Mateus (Author) FCUP; Victor de Freitas (Author) FCUP; Tawara, MH (Author) Other; Fernandez Megia, E (Author) Other

Journal

Title: ACS Applied Polymer Materials

Vol. 3

Pages: 1457-1464

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 6 Citations

Other information

Authenticus ID: P-00T-RPK

DOI: 10.1021/acsapm.0c01321

Abstract (EN): Anionic dendrimers have recently emerged as hosts (H) for the color stabilization of the flavylium cation of anthocyanin guests (G). The interaction with a promising, more hydrophobic pyranoanthocyanin illustrates how the structure and concentration of the dye modulate the host-guest interaction mechanisms. NMR and UV-vis titrations (host over guest, from G/H ratio 2089 to 45) showed that at relatively low dendrimer-to-dye concentrations, ion pairs at the dendrimer periphery prevail over dye encapsulation. This promotes the deaggregation of the dye, not previously observed with anthocyanins, and related to the more hydrophobic nature of this dye (deshielding of the dye H-1 signals, higher T-2 relaxation times, constant diffusion coefficient). As the dendrimer concentration increases, the dye encapsulation, earlier unseen with structurally simpler flavylium dyes, becomes dominant (shielding and broadening of the dye H-1 signals and lower T-2 and diffusion coefficient). The interaction parameters of the encapsulation process (K similar to 4.51 X 10(4) M-1, n similar to 150) indicate the binding of ca. one pyranoanthocyanin molecule by each sulfate terminal group. Our results provide insights into the ability of dendrimers to host structurally diverse pyranoflavylium-based dyes and how the structure of the latter modulates the range of interactions involved. The encapsulation ability of this dendrimer to such pH-sensitive dyes is envisioned for the host-guest sensing applications such as pH-responsive systems used for example in food smart packaging.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8