Optimization of ultrasound-assisted extraction of phenolic compounds from fresh Moringa oleifera leaves with a response surface methodology and comparison with the Soxhlet extraction method

Abstract

ABSTRACT. The present study evaluated the optimum conditions of ultrasound-assisted extraction (UAE) and Soxhlet extraction (SE) of antioxidant capacities and total phenolics from fresh Moringa oleifera leaves, using the response surface methodology. Spectrophotometric method with Folin–Ciocalteu and 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagents was used to determine the total phenolic content (TPC) and the antioxidant activity (AA), respectively. The four models obtained showed the non-linear and quadratic dependences of both measured responses (TPC and AA) which were influenced significantly by all control variables including the acetone solvent (70%, v/v) to solid (SS) ratio, extraction time, and extraction temperature of both extraction methods. Furthermore, at the same extraction temperature, the extraction efficacy of UAE was better than SE as significantly shorter extraction time, less extraction solvent, but higher bio-active content was experienced. The optimal UAE conditions included a SS ratio of 31:1 (mL/g), extraction time of 26 min, and extraction temperature of 59 oC, resulting in the maximum TPC (34.36 mg GAE/g dry weight, DW) and AA (491.9 µmol TE/g DW) in the extracts. In addition, the models proposed were considered to be accurate and reliable for predicting the TPC and AA of fresh M. oleifera leaf extract. The research findings also imply potential applications for ultra-sonication extraction to produce the extracts from fresh M. oleifera leaves for pharmaceutical industry as well as food technology.
  
 KEY WORDS: Antioxidant activity, Herbal plant, Model, Polyphenols, RSM
  
 Bull. Chem. Soc. Ethiop. 2022, 36(2), 261-275.                                                               
 DOI: https://dx.doi.org/10.4314/bcse.v36i2.2