Anthocyanin Color Stabilization by Host-Guest Complexation with p-Sulfonatocalix[n]arenes

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

Authors

Mendoza, J (Author) Other; Luis Cruz (Author) FCUP; Victor de Freitas (Author) FCUP; Pina, F (Author) Other; Basilio, N (Author) Other

Journal

Title: Molecules

Vol. 11

Final page: 5389

ISSN: 1420-3049

Publisher: MDPI

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 5 Citations

Other information

Authenticus ID: P-00V-DB1

DOI: 10.3390/molecules26175389

Abstract (EN): Flavylium-based compounds in their acidic and cationic form bring color to aqueous solutions, while under slightly acidic or neutral conditions they commonly bring discoloration. Selective host-guest complexation between water-soluble p-sulfonatocalix[n]arenes (SCn) macrocycles and the flavylium cationic species can increase the stability of the colored form, expanding its domain over the pH scale. The association constants between SCn and the cationic (acid) and neutral basic forms of flavylium-based compounds were determined through UV-Vis host-guest titrations at different pH values. The affinity of the hosts for synthetic chromophore was found to be higher than for a natural anthocyanin (Oenin). The higher affinity of SC4 for the synthetic flavylium was confirmed by H-1 NMR showing a preferential interaction of the flavylium phenyl ring with the host cavity. In contrast with its synthetic counterpart, the flavylium substitution pattern in the anthocyanin seems to limit the inclusion of the guest in the host's binding pocket. In this case, the higher affinity was observed for the octamer (SC8) likely due to its larger cavity and higher number of negatively charged sulfonate groups.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10