Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Onion (Allium cepa L.) Skin Waste Valorization: Unveiling the Phenolic Profile and Biological Potential for the Creation of Bioactive Agents through Subcritical Water Extraction

Esther Trigueros
* ORCID logo ,
Óscar Benito-Román
ORCID logo ,
Andreia P. Oliveira
ORCID logo ,
Romeu A. Videira
ORCID logo ,
Paula B. Andrade
ORCID logo ,
M. Teresa Sanz
ORCID logo ,
Sagrario Beltrán
ORCID logo
Version 1 : Received: 31 January 2024 / Approved: 31 January 2024 / Online: 1 February 2024 (10:00:45 CET)

A peer-reviewed article of this Preprint also exists.

Trigueros, E.; Benito-Román, Ó.; Oliveira, A.P.; Videira, R.A.; Andrade, P.B.; Sanz, M.T.; Beltrán, S. Onion (Allium cepa L.) Skin Waste Valorization: Unveiling the Phenolic Profile and Biological Potential for the Creation of Bioactive Agents through Subcritical Water Extraction. Antioxidants 2024, 13, 205. Trigueros, E.; Benito-Román, Ó.; Oliveira, A.P.; Videira, R.A.; Andrade, P.B.; Sanz, M.T.; Beltrán, S. Onion (Allium cepa L.) Skin Waste Valorization: Unveiling the Phenolic Profile and Biological Potential for the Creation of Bioactive Agents through Subcritical Water Extraction. Antioxidants 2024, 13, 205.

Abstract

Onion skin waste (OSW), the primary non-edible byproduct from onion processing, offers a renewable source of bioactive compounds. This study aims to valorize OSW through subcritical water extraction (SWE), aligning with circular economy and biorefinery principles. SWE was carried out at 145 °C, 50 bar and 50 min in a discontinuous reactor, producing a phenolic-rich extract (32 ± 3 mg/g), dominated by protocatechuic acid (20 ± 3 mg/g), quercetin-4´-O-glucoside (7.5 ± 0.2 mg/g), and quercetin (3.2 ± 0.6 mg/g). Additionally, it contains sugars (207 ± 20 mg sucrose-Eq/g), proteins (22.8 ± 1.6 mg BSA-Eq/g) and free amino acids (20.4 ± 1.2 mg arginine-Eq/g). Its phenolic richness determines its scavenging activity against ●NO and O2●- radicals, and its α-glucosidase and aldose-reductase inhibition without affecting α-amylase. Notably, the extract demonstrates significant α-glucosidase inhibition (IC50 = 76 ± 4 µg/mL), surpassing acarbose (IC50 = 129.5 ± 1.0 µg/mL), in both pure enzyme and cell culture tests without showing cytotoxicity on AGS, HepG2 and Caco-2 human cell lines. The extract’s bioactivity and nutritional content make it suitable for developing antioxidant and antidiabetic nutraceutical/food components, highlighting the SWE potential for OSW valorization without using organic solvents.

Keywords

hydrothermal treatment; onion waste; polyphenols; quercetin; antioxidant activity; antidiabetic potential

Subject

Biology and Life Sciences, Food Science and Technology

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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