{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T10:10:49Z","timestamp":1779271849032,"version":"3.51.4"},"reference-count":42,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T00:00:00Z","timestamp":1779235200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Science and Technology Research Program of Hubei Provincial Department of Education","award":["B2022226"],"award-info":[{"award-number":["B2022226"]}]},{"name":"Key Project of Education Science Planning in Hubei Province","award":["2022GA084"],"award-info":[{"award-number":["2022GA084"]}]},{"name":"National College Student Innovation and Entrepreneurship Training Project","award":["202410518003"],"award-info":[{"award-number":["202410518003"]}]},{"name":"Hubei Province Excellent Young and Middle aged Science and Technology Innovation Team Program Funding Project","award":["T202024"],"award-info":[{"award-number":["T202024"]}]},{"name":"Synthesis and Application Performance Verification of Highly Efficient Heavy Metal Chelating Functional Monomers Based on Natural Flavonoids","award":["2026HX032"],"award-info":[{"award-number":["2026HX032"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Membranes"],"abstract":"<jats:p>This study used UV-Vis absorption spectroscopy to investigate the interactions of flavonoids\u2014baicalein (with ortho-dihydroxyl on the A-ring) and apigenin (with 4\u2032-monohydroxyl on the B-ring)\u2014with metal ions (Co2+, Ce4+) and membrane\u2013mimetic systems (CTAB\/SDS micelles, liposomes, vesicles). It revealed how flavonoid spectral properties related to molecular structure and microenvironment. Key findings were as follows: pH affected absorption spectra by altering phenolic hydroxyl protonation. Metal chelation depended on hydroxyl position: baicalein\u2019s A-ring ortho-dihydroxyl formed a stable charge-transfer complex with Cu2+. In acidic medium, apigenin reduced Ce(IV) more effectively than baicalein, which contradicted the classic antioxidant role of ortho-dihydroxyl groups. This showed that reaction microenvironments could change hydroxyl reactivity and electron transfer paths. Membrane\u2013mimetic systems (liposomes\/vesicles) raised apparent pKa, enhanced solubility and stability. The study first quantified distinct \u0394pKa values for different flavonoids (e.g., quercetin vs. baicalein), which were linked to intramolecular H-bonding and membrane preference. Quercetin\u2019s B-ring ortho-dihydroxyl enabled the formation of hydrophobic interfacial anions in nanocarriers under alkaline pH, ensuring high stability. Kaempferol showed sustained leakage. These findings provided a basis for structure-guided flavonoid carrier design, bioavailability, and antioxidant delivery. By integrating reaction microenvironment, membrane interface effects, and carrier stability, this work clarified flavonoid bioactivity mechanisms and supported targeted delivery strategies.<\/jats:p>","DOI":"10.3390\/membranes16050179","type":"journal-article","created":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T09:12:41Z","timestamp":1779268361000},"page":"179","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Probing Flavonoid-Metal and Membrane Interactions by UV-Vis Spectroscopy: Structural Insights into Bioactivity and Bioavailability"],"prefix":"10.3390","volume":"16","author":[{"given":"Shuangmei","family":"Gong","sequence":"first","affiliation":[{"name":"Research Center for Preparation and Properties of New Functional Materials, Hanjiang Normal University, Shiyan 442000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiulong","family":"Ou","sequence":"additional","affiliation":[{"name":"Research Center for Preparation and Properties of New Functional Materials, Hanjiang Normal University, Shiyan 442000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"132531","DOI":"10.1016\/j.foodchem.2022.132531","article-title":"Plant flavonoids: Classification, distribution, biosynthesis, and antioxidant activity","volume":"383","author":"Shen","year":"2022","journal-title":"Food Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2075","DOI":"10.2174\/1568026623666230710162217","article-title":"Therapeutic Potential and Molecular Mechanisms of the Multitargeted Flavonoid Fisetin","volume":"23","author":"Rauf","year":"2023","journal-title":"Curr. 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