Enhancing phenolic compounds recovery from Arnica montana L. flowers through optimized green extraction protocols

The present study aimed to optimize the extraction conditions (time, temperature, and ethanol concentration) of pressurized-liquid and microwave-assisted extraction (PLE and MAE, respectively) to maximize the recovery of phenolic compounds from Arnica montana flowers. To this aim, response surface methodology (RSM) with an experimental design was applied. The studied variable responses were extraction yield and total phenolic content (TPC), expressed as mg/g of sample dry weight (dw) and mg/g of extract. For PLE, the models showed a good adjusted R² coefficient (0.75–0.92) and no significant lack of fit. MAE models also showed good adjustment, except for TPC expressed per g of dw, where the model showed a significant lack of fit and was not suitable for optimization. The optimal PLE conditions that maximized all response variables were 11 min, 125 °C and 76 % ethanol in water. For MAE, the optimal conditions were 25 min, 115 °C, and 76 % ethanol. Comparing the predicted values, PLE significantly surpassed MAE in terms of TPC, obtaining 389 compared to 246 mg of total phenolics/g of extract for MAE. Validation experiments confirmed the suitability of the predictive models. In the case of PLE, employing extraction cycles under optimal conditions improved phenolic compound extraction, with three extraction cycles leading to a 104 % increase in TPC. Overall, the optimized PLE protocol was considered an efficient methodology for obtaining rich-phenolic extracts, contributing to the expansion of current industrial applications of A. montana.