Thermal Degradation Kinetics and pH-Rate Profiles of Iriflophenone 3,5-C-β-d-diglucoside, Iriflophenone 3-C-β-d-Glucoside and Mangiferin in Aquilaria crassna Leaf Extract.

The health benefits of the Aquilaria crassna Pierre ex Lecomte leaf extract (AE) make it very useful as an ingredient in food and pharmaceutical products. Iriflophenone 3,5-C-β-d-diglucoside (1), iriflophenone 3-C-β-d-glucoside (2) and mangiferin (3) are bioactive compounds of AE. We assessed the stability of AE by investigating the thermal degradation kinetics and shelf-life (t90%) of compounds 1, 2 and 3 using Arrhenius plot models and studied their pH-rate profiles. The results demonstrate that 1 and 2 were degraded, following a first-order kinetic reaction. The degradation of 3 followed first-order reaction kinetics when present in a solution and second-order reaction kinetics in the dried powder form of the extract. According to the first-order kinetic model, the predicted shelf-life (t90%) of the extract at 25 °C in dried form for compound 1 was 989 days with activation energy 129.86 kJ·mol-1, and for 2 it was 248 days with activation energy 110.57 kJ·mol-1, while in the extract solution, the predicted shelf-life of compounds 1-3 was 189, 13 and 75 days with activation energies 86.83, 51.49 and 65.28 kJ·mol-1, respectively. In addition, the pH-rate profiles of 1-3 indicated that they were stable in neutral to acidic environments.