Microwave-assisted deep eutectic solvent extraction of phenolic antioxidants from onion (Allium cepa L.) peel: a Box–Behnken design approach for optimization

  • Chandra Bhushan T. Pal
  • Girirajsinh C. JadejaEmail author
Original Article


Valorization of onion peel waste, considered to be a rich source of polyphenolic compounds, by employing green extraction techniques is the need of the hour. The aim of the present study was to optimize the microwave-assisted extraction of bioactive phenolic compounds from onion peel wastes employing ChCl:Urea:H2O deep eutectic solvent. Microwave power (100–200–300 W), time (5–15–25 min) and liquid to solid ratio (40:1–50:1–60:1) were studied as the major parameters affecting the extraction efficiency. A Box–Behnken design was adopted including 17 experiments with five centre points. The optimum conditions determined were 100 W microwave power, 15.03 min irradiation time and 54.97 mL g−1 liquid to solid ratio. Under the MAE optimized conditions, the recovery of TPC and FRAP were 80.45 (mg GAE g−1 dw) and 636.18 (µmol AAE g−1 dw), respectively. Morphology of onion peels before and after DES extraction were also studied to gain an insight in the effect of microwave irradiations on the biomass.


Onion peel Deep eutectic solvents Microwave-assisted deep eutectic solvent extraction Total phenolic content Antioxidant activities Response surface methodology 



Ascorbic acid equivalents


Box–Behnken design


Choline chloride:urea


Deep eutectic solvent


Ethyl acetate


Ferric reducing antioxidant power


Gallic acid equivalents


Hydrogen bond acceptor


Hydrogen bond donors


High performance liquid chromatography


Heating–stirring extraction


Liquid–liquid extraction


Microwave-assisted deep eutectic solvent extraction


Microwave-assisted extraction


Phenolic compounds


Response surface methodology


Scanning electron microscopy


Total phenolic content





The authors gratefully acknowledge the support of Dr. N. A. Gajbhiye, Senior Scientist (Organic Chemistry), ICAR-Directorate of Medicinal & Aromatic Plants Research, Anand, Gujarat by providing necessary facilities for HPLC analysis of the samples and help rendered in analytical determinations.

Supplementary material

13197_2019_3891_MOESM1_ESM.docx (24 kb)
Supplementary material 1 (DOCX 24 kb)


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Copyright information

© Association of Food Scientists & Technologists (India) 2019

Authors and Affiliations

  • Chandra Bhushan T. Pal
    • 1
  • Girirajsinh C. Jadeja
    • 1
    Email author
  1. 1.Chemical Engineering DepartmentS. V. National Institute of TechnologySuratIndia

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