*Article* **Optimization of Ultrasound-Assisted Extraction of Polyphenols from** *Myrtus communis* **L. Pericarp**

#### **Nadia Bouaoudia-Madi 1, Lila Boulekbache-Makhlouf 1,\*, Khodir Madani 1, Artur M.S. Silva 2, Sofiane Dairi 1,3, Sonia Oukhmanou–Bensidhoum 1 and Susana M. Cardoso 2,\***

1 Laboratoire de Biomathématiques, Biophysique, Biochimie, et Scientométrie (L3BS), FacultédesSciencesdelaNatureetdelaVie,UniversitédeBejaia,06000Bejaia,Algeria

 2 QOPNA&LAQV-REQUIMTE,DepartmentofChemistry,UniversityofAveiro,3810-193Aveiro,Portugal


Received: 17 May 2019; Accepted: 26 June 2019; Published: 2 July 2019

**Abstract:** Response surface methodology (RSM) was used to optimize the extraction of phenolics from pericap of *Myrtus communis* using ultrasound-assisted extraction (UAE). The results were compared with those obtained by microwave-assisted extraction (MAE) and conventional solvent extraction (CSE) methods. The individual compounds of the optimized extract obtained by UAE were identified by ultra-high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (UHPLC-DAD-ESI-MSn). The yield of total phenolic compounds (TPC) was a ffected more significantly by ethanol concentration, irradiation time, liquid solvent-to-solid ratio (*p* < 0.0001) and amplitude (*p* = 0.0421) and optimal parameters conditions set by the RSM model were 70% (*v*/*v*), 7.5 min and 30%, respectively. The experimental yield of TPC (241.66 ± 12.77 mg gallic acid equivalent/g dry weight) confirmed the predicted value (235.52 ± 9.9 mg gallic acid equivalent/g dry weight), allowing also to confirm the model validity. Under optimized conditions, UAE was more e fficient than MAE and CSE in extracting antioxidants, which comprised mostly myricetin glycosides. Globally, the present work demonstrated that, compared to MAE and CSE, UAE is an e fficient method for phenolic extraction from *M. communis* pericarp, enabling to reduce the working time and the solvent consumption.

**Keywords:** myrtle; ultrasound-assisted extraction; phenolic compounds; antioxidant capacity; liquid chromatography analysis; mass spectrometry
