Comparative Study of Microwave-Assisted Extraction and Ultrasound-Assisted Extraction Techniques (MAE vs. UAE) for the Optimized Production of Enriched Extracts in Phenolic Compounds of Camellia japonica var Eugenia de Montijo

Camellia japonica is an underexplored medicinal plant with associated bioactivities. Innovative approaches are proposed in regard to the large-scale application of C. japonica, being one of the main routes for the extraction of phenolic compounds. The optimum conditions for the extraction of phenolic compounds from the flowers of C. japonica var. Eugenia de Montijo were determined using the response surface methodology (RSM). A five-level experimental design was carried out and analyzed via RSM using, as variables, temperature (T), time (t) and solvent (S), in the case of microwave-assisted extraction (MAE), and power (P), t and S in the case of ultrasound-assisted extraction (UAE). The compounds were identified using HPLC–MS–MS. Two responses were studied: the extraction yield and concentration of phenolic compounds. The results showed that the maximum yields (80%) were obtained at high temperatures and low times (180 °C, 5 min) when using MAE. Lower yields (56%) were obtained using UAE (optimal conditions 62% amplitude, 8 min, 39% acidified ethanol). The main family of phenolic compounds were flavonols. Moreover, the present study contributes to the valorization of underused flower species commonly present in the North-West region of Spain, by obtaining extracts rich in phenolic compounds that can be potentially applied as ingredients in different industrial fields.