The knowledge of acid-base dissociation constants, that are characteristic of specific groups or of a combination of groups, is important to fully understand the properties of a molecule in a biological system. In this work, acidity constants of nine flavanones were determined by performing potentiometric titrations in both pH ways, from acid to base and vice versa. The evaluation was carried out in aqueous media (i.e. 0.16 M NaCl) at 37 degrees C in a wide pH range (from 2 to 9). Results obtained allow the experimental pKa assignation to hydroxyl groups belonging to selected flavanones, namely naringenin, hesperetin and eriodictyol, as well as their corresponding glycosides and 3-hydroxy-3-methyl glutaryl (HMG) derivatives: naringin, neohesperidin and neoeriocitrin, and melitidin, brutieridin and peripolin, respectively. To confirm the experimental results, quantum chemical calculations were additionally performed on aglycones and on HMG-containing compounds. The well-known instability of these analytes in basic solution produces some differences between the pKa values obtained in this work and those obtained under different experimental approaches previously reported.
Acidity constants of hydroxyl groups placed in nine selected flavanones from citrus fruits
Bartella L.;Malacaria L.;Elliani R.;Prejano M.;Santoro I.;Di Donna L.;Marino T.;Furia E.
2025-01-01
Abstract
The knowledge of acid-base dissociation constants, that are characteristic of specific groups or of a combination of groups, is important to fully understand the properties of a molecule in a biological system. In this work, acidity constants of nine flavanones were determined by performing potentiometric titrations in both pH ways, from acid to base and vice versa. The evaluation was carried out in aqueous media (i.e. 0.16 M NaCl) at 37 degrees C in a wide pH range (from 2 to 9). Results obtained allow the experimental pKa assignation to hydroxyl groups belonging to selected flavanones, namely naringenin, hesperetin and eriodictyol, as well as their corresponding glycosides and 3-hydroxy-3-methyl glutaryl (HMG) derivatives: naringin, neohesperidin and neoeriocitrin, and melitidin, brutieridin and peripolin, respectively. To confirm the experimental results, quantum chemical calculations were additionally performed on aglycones and on HMG-containing compounds. The well-known instability of these analytes in basic solution produces some differences between the pKa values obtained in this work and those obtained under different experimental approaches previously reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
