Optimization and Kinetic Modelling of Total Phenols and Flavonoids Extraction from Tilia cordata M. Flowers

Abstract

The main goal was to optimize and establish the kinetics and the thermodynamics of the extraction process. An investigation into the effects of ethanol  concentration (0–100 %), liquid to solid ratio (30–60 mL g^–1), extraction temperature (25–65 °C), and extraction time (40–200 min) on the extraction of total  phenols (TP) and total flavonoids (TF) from linden (Tilia cordata M.) flowers was performed using single-factor experiments. Experimental results  showed that extraction conditions had a significant effect on the extraction of phenolic compounds. The optimized conditions were 50 % ethanol, liquid  to solid ratio 60 mL g^–1 for 120 min at 55 °C, with values of 17.05 mg GAE g^–1 dry weight (d.w.) for TP and 13.32 mg CE g^–1 d.w. for TF. Extracted phenolic  compounds were analyzed by HPLC. The antioxidant activity of the extracts was evaluated by DPPH and ABTS assays. The applicability of different  mathematical models (model based for the unsteady diffusion through the plant material, model based on the film theory and model of Ponomaryov) to  describe the kinetics of the extraction process of TP and TF from linden flowers was studied as well. The mathematical models applied showed a good  agreement with the experimental results, which allows their application in modelling and optimizing the solid/liquid extraction process to extract TP and  TF from linden flowers.