University of Oulu

Dou Jinze, Varila Toni, Salminen Juha-Pekka, Tuomikoski Sari, Hietala Sami, Hemmi Maria, Hu Tao, Lassi Ulla, Vuorinen Tapani, Willow bark proanthocyanidins with potential for water treatment: Chemical characterization and zinc/bisphenol A removal, Separation and Purification Technology, Volume 318, 2023, 123943, ISSN 1383-5866,

Willow bark proanthocyanidins with potential for water treatment : chemical characterization and zinc/bisphenol A removal

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Author: Dou, Jinze1; Varila, Toni2,3; Salminen, Juha-Pekka4;
Organizations: 1Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
2Research Unit of Sustainable Chemistry, University of Oulu, Oulu, Finland
3Kokkola University Consortium Chydenius, University of Jyväskylä, Kokkola, Finland
4Natural Chemistry Research Group, Department of Chemistry, University of Turku, Turku, Finland
5Department of Chemistry, University of Helsinki, Helsinki, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 5.7 MB)
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Language: English
Published: Elsevier, 2023
Publish Date: 2023-05-11


This study investigates the chemical structure of proanthocyanidin-rich crude extracts from willow bark and these materials were tested initially as adsorbents for artificial (waste)water treatment. The crude extracts were obtained through mild water extraction and the colorant fractions were further chromatographically fractionated to understand the chemical structure of the willow bark proanthocyanidins. The chemistry of crude extracts and purified fractions were investigated using nuclear magnetic resonance (NMR) and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Both NMR (liquid and solid-state) and UPLC-MS/MS suggest that the crude extracts constitute of interflavan linked flavan-3-ols, i.e. proanthocyanidins with both procyanidin (PC)-type and prodelphinidin (PD)-type subunits, with the PC/PD ratio of approximately 2.3–2.5. PD-type proanthocyanidins were detected from the purified colorant fractions only with UPLC-MS/MS. Both the UPLC-MS/MS and size exclusion chromatography suggest that the crude extracts have an average oligomerization degree of roughly 5–6 flavan-3-ol units. Adsorption experiments showed that the activated foams made of crude extracts were effective in removing both zinc and Bisphenol A (BPA) with removal efficiencies of roughly 80–90% and thus these willow bark-derived proanthocyanidins are promising in water treatment. The significance of this study suggests the upgrading use of crude extracts for water treatment could significantly improve the value of willow bark.

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Series: Separation and purification technology
ISSN: 1383-5866
ISSN-E: 1873-3794
ISSN-L: 1383-5866
Volume: 318
Article number: 123943
DOI: 10.1016/j.seppur.2023.123943
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
Funding: This work was a part of the Academy of Finland's Flagship Programme under Project No. 318890 and No. 318891 (Competence Center for Materials Bioeconomy, FinnCERES).
Copyright information: © 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (