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Article

Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities

by
Mariana Gois Ruivo da Silva
1,
Mihaela Skrt
1,
Draženka Komes
2,
Nataša Poklar Ulrih
1,3 and
Lea Pogačnik
1,*
1
Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
2
Department of Food Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, 10000 Zagreb, Croatia
3
The Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins, 1000 Ljubljana, Slovenia
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(8), 2909; https://doi.org/10.3390/ijms21082909
Submission received: 30 March 2020 / Revised: 17 April 2020 / Accepted: 20 April 2020 / Published: 21 April 2020

Abstract

There is increasing concern for reduction of the ecological impacts of industrial waste caused by fruits and vegetables. To reduce costs of onion waste disposal while obtaining value-added products, onion skin can be used to extract quercetin, a natural flavonoid with antioxidant, anti-inflammatory and anti-cancer effects. The aim was to optimize quercetin extraction from brown onion (Allium cepa L.) skin through investigation of the effects of different parameters on quercetin yield. Operational parameters for conventional maceration extraction and for ultrasound-assisted extraction were compared: solvent type, mass-to-liquid ratio, extraction time and temperature. Antioxidant capacity was determined using DPPH· radical scavenging assays and quercetin yield using HPLC/DAD. Anti-α-amylase activity of onion skin extracts was investigated using α-amylase inhibition assays. Optimal extraction conditions of quercetin from onion skin were obtained with maceration extraction, 50% ethanol, 1:100 mass-to-liquid ratio, 25 °C, for 15 min. Under these conditions, the antioxidant capacity (expressed as quercetin equivalents) was 18.7 mg/g and the mass fraction of quercetin was 7.96 mg/g. The onion skin extracts showed a dose-dependent relationship between dry extract concentration and α-amylase inhibition, which confirms that this onion skin extract can be considered as an anti-diabetes agent.
Keywords: Allium cepa L.; anti-α-amylase activity; antioxidant capacity; extraction optimization; quercetin Allium cepa L.; anti-α-amylase activity; antioxidant capacity; extraction optimization; quercetin
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MDPI and ACS Style

Gois Ruivo da Silva, M.; Skrt, M.; Komes, D.; Poklar Ulrih, N.; Pogačnik, L. Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities. Int. J. Mol. Sci. 2020, 21, 2909. https://doi.org/10.3390/ijms21082909

AMA Style

Gois Ruivo da Silva M, Skrt M, Komes D, Poklar Ulrih N, Pogačnik L. Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities. International Journal of Molecular Sciences. 2020; 21(8):2909. https://doi.org/10.3390/ijms21082909

Chicago/Turabian Style

Gois Ruivo da Silva, Mariana, Mihaela Skrt, Draženka Komes, Nataša Poklar Ulrih, and Lea Pogačnik. 2020. "Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities" International Journal of Molecular Sciences 21, no. 8: 2909. https://doi.org/10.3390/ijms21082909

APA Style

Gois Ruivo da Silva, M., Skrt, M., Komes, D., Poklar Ulrih, N., & Pogačnik, L. (2020). Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities. International Journal of Molecular Sciences, 21(8), 2909. https://doi.org/10.3390/ijms21082909

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