{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:59:26Z","timestamp":1785405566342,"version":"3.56.0"},"reference-count":43,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T00:00:00Z","timestamp":1782777600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Spanish State Research Agency (AEI) from the Ministry of Science, Innovation, and Universities","award":["PID2021-127566NB-I00"],"award-info":[{"award-number":["PID2021-127566NB-I00"]}]},{"award":["PID2021-127566NB-I00"],"award-info":[{"award-number":["PID2021-127566NB-I00"]}],"id":[{"id":"https:\/\/ror.org\/004f1q697","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antioxidants"],"abstract":"<jats:p>Deep eutectic solvents (DES) emerge as sustainable alternatives for antioxidant polyphenol extraction; however, their analytical performance and compatibility with antioxidant assays remain insufficiently characterized. A choline chloride-urea-water DES (1:2:4) was compared with 70% ethanol for extracting polyphenols from onion bulbs and peels from cultivars grown in Spain and North Macedonia. Extraction conditions were selected through a comparative evaluation of vortex- and ultrasound-assisted extraction and benchmarked against conventional ethanolic stirring (2 h). Two-way ANOVA identified solvent composition as the main determinant of total phenolic content (F(1,20) = 1526.28, p &lt; 0.001), while extraction method significantly influenced recovery under DES conditions (F(2,30) = 408.52, p &lt; 0.001). The selected UAE-DES protocol increased TPC up to 2.2-fold and reduced extraction time to &lt;5 min. TPC ranged from 25 to 44 mg GAE\/g dw in bulbs and 42\u201362 mg GAE\/g dw in peels, with red cultivars showing the highest values. UHPLC-MS\/MS revealed solvent-dependent selectivity: ethanol favored flavonols (quercetin 5\u201311 mg\/g dw), whereas DES enhanced phenolic acids (gallic acid up to 0.3 mg\/g dw; protocatechuic acid up to 7 mg\/g dw). FRAP correlated with TPC (r = 0.64\u20130.92), while ABTS was incompatible with DES extracts. Storage reduced TPC by 45\u201375% but preserved cultivar ranking. These findings demonstrate that UAE-DES enables rapid and efficient polyphenol recovery while highlighting the need to validate antioxidant assays in non-conventional solvents.<\/jats:p>","DOI":"10.3390\/antiox15070826","type":"journal-article","created":{"date-parts":[[2026,7,1]],"date-time":"2026-07-01T03:06:34Z","timestamp":1782875194000},"page":"826","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Green Ultrasound-Assisted Extraction of Onion Polyphenols Using a Choline Chloride-Urea Deep Eutectic Solvent: Extraction Efficiency, Solvent Selectivity, and Antioxidant Assay Compatibility"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3581-558X","authenticated-orcid":false,"given":"Mirjana S.","family":"Jankulovska","sequence":"first","affiliation":[{"name":"Faculty of Agricultural Sciences and Food\u2014Skopje, Ss. Cyril and Methodius University in Skopje, P.O. Box 297, 1000 Skopje, North Macedonia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0283-6103","authenticated-orcid":false,"given":"Raquel","family":"S\u00e1nchez-Romero","sequence":"additional","affiliation":[{"name":"Department of Analytical Chemistry, Nutrition and Food Sciences, University of Alicante, P.O. Box 99, 03080 Alicante, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5915-351X","authenticated-orcid":false,"given":"Gabriela","family":"Guillena","sequence":"additional","affiliation":[{"name":"Department of Organic Chemistry, University of Alicante, P.O. Box 99, 03080 Alicante, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9151-7050","authenticated-orcid":false,"given":"Jos\u00e9 Luis","family":"Todol\u00ed-Torr\u00f3","sequence":"additional","affiliation":[{"name":"Department of Analytical Chemistry, Nutrition and Food Sciences, University of Alicante, P.O. Box 99, 03080 Alicante, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"506","DOI":"10.3945\/an.112.002154","article-title":"Health benefits of fruits and vegetables","volume":"3","author":"Slavin","year":"2012","journal-title":"Adv. Nutr."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"384S","DOI":"10.3945\/an.112.003517","article-title":"Health-Promoting Components of Fruits and Vegetables in the Diet","volume":"4","author":"Liu","year":"2013","journal-title":"Adv. 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