Synergistic effects of enzyme-based ultrasonic-assisted extraction of phenolic compounds from Rhododendron arboreum and evaluation of thermal kinetic stability

Abstract

Rhododendron arboreum Smith flowers constitute a valuable dietary supplement or food additive and are novel therapeutic agents. The present work demonstrates and optimizes an effective, enzyme-based ultrasonic approach for polyphenols extraction as a potential alternative to conventional extraction methods. Enzyme-based extraction constitutes an efficient, benign, sustainable, and eco-friendly extraction technology. A Box-Benkhen design with 31 experimental runs was used to investigate and optimize parameters such as solvent concentration (50–90%), solvent-to-sample ratio (10:1 mL/g-60:1 mL/g), enzyme concentration (0.25–1.25%), and extraction temperature (35ºC-55ºC). Under linear, quadratic, and interaction effects, the extraction parameters have a significant (p < 0.05) impact on polyphenol extraction. The model demonstrated good fitness, with a significant model F-value (p < 0.05) and a non-significant lack of fit. The phenolic composition of the extract was quantified using High-Performance Liquid Chromatography – Photo Diode Array (HPLC-PDA), among which catechin (33.64 mg/g) was recorded as the most abundant polyphenol, followed by gallic acid (23.92 mg/g), while caffeic acid (0.55 mg/g) was the least. In addition, thermal stability kinetics experimentation revealed that phytochemicals and the antioxidant properties of R. arboreum were thermally stable even at 80ºC. The first-order kinetic model in terms of reaction rate constant was determined to describe the stability mechanism, and the latter Arrhenius model was computed to determine respective activation energies. Overall, the findings of this study revealed that enzyme-based extraction could be investigated as a cutting-edge, environmentally friendly technology for recovering optimal amounts of phenolic compounds, with potential applications in the formulation of health-promoting beverages and modulating functional food derivatives at a larger scale.