Thermal Degradation Kinetics and pH–Rate Profile of Verbascoside and Stability Improvement by Solid Lipid Nanoparticles

Abstract

Thermal degradation of verbascoside (VB) in Acanthus ebracteatus Vahl (AE) always affects its health benefit. Here the temperature effect on VB in both AE extract and solid lipid nanoparticles (SLNs)-encapsulated AE extract was demonstrated using the Arrhenius plot. The reaction rate constants were calculated for shelf life and plotted to obtain pH−rate profiles. VB degradation was a first-order reaction. The reaction rate in a neutral to alkaline solution was faster than in an acidic solution. VB in AE extract-loaded SLNs was more stable than in uncapped AE extract. The shelf life of VB in SLNs was 153 days with activation energy (E a ) of 76.16 kJ mol −1 , whereas those of VB in AE extract and in AE extract solution were 75 days with E a = 78.03 kJ mol −1 and 12 days with E a = 49.24 kJ mol −1 , respectively. Therefore, we anticipate that the AE extract-loaded SLNs will be beneficial for product development.

Effect of heat treatment on phenolic composition and radical scavenging activity of olive leaf extract at different pH conditions: a spectroscopic and kinetic study

“…The higher verbascoside hydrolysis rate at neutral or mildly alkaline pH conditions has been previously observed and is related to the breakage of the glycosidic bond between the disaccharide and the phenylethanoid group. [26][27][28] The results at 50 °C are not shown, but demonstrated a similar pH-dependent response to those at 70 °C and 90 °C, with an oleuropein degradation at pH 2.0 from 844 ± 5 μg mL −1 to 628 ± 5 μg mL −1 after 90 min of treatment (approximately25% loss). Similarly to results observed at higher temperatures, the oleuropein hydrolysis rate was much slower at pH 4.0 and 6.0, showing no significant degradation at 50 °C.…”

“…With regard to verbascoside, it showed a high thermal stability at lower pH values, whereas it underwent extensive degradation at pH 6.0, as observed also at 70 °C, decreasing from 41 ± 1 μg mL −1 to 8.9 ± 0.1 μg mL −1 after 180 min (approximately 80% loss). The higher verbascoside hydrolysis rate at neutral or mildly alkaline pH conditions has been previously observed and is related to the breakage of the glycosidic bond between the disaccharide and the phenylethanoid group 26‐28 …”