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This study demonstrated the antibacterial and antiviral potential of condensed tannins and tannic acid when incorporated into fiber networks tested for functional material purposes. Condensed tannins were extracted from industrial bark of Norway spruce by using pressurized hot water extraction (PHWE), followed by purification of extracts by using XADHP7 treatment to obtain sugar-free extract. The chemical composition of the extracts was analyzed by using HPLC, GC‒MS and UHPLC after thiolytic degradation. The test matrices, i.e., lignocellulosic handsheets, were produced and impregnated with tannin-rich extracts, and tannic acid was used as a commercial reference. The antibacterial and antiviral efficacy of the handsheets were analyzed by using bioluminescent bacterial strains ( Staphylococcus aureus RN4220+pAT19 and Escherichia coli K12+pCGLS11) and Enterovirus coxsackievirus B3. Potential bonding of the tannin-rich extract and tannic acid within the fiber matrices was studied by using FTIR-ATR spectroscopy. The deposition characteristics (distribution and accumulation patterns) of tannin compounds and extracts within fiber networks were measured and visualized by direct chemical mapping using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and digital microscopy. Our results demonstrated for the first time, how tannin-rich extracts obtained from spruce bark side streams with green chemistry possess antiviral and antibacterial properties when immobilized into fiber matrices to create substitutes for plastic hygienic products, personal protection materials such as surgical face masks, or food packaging materials to prolong the shelf life of foodstuffs and prevent the spread of infections. However, more research is needed to further develop this proof-of-concept to ensure stable chemical bonding in product prototypes with specific chemistry., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jyske, Liimatainen, Tienaho, Brännström, Aoki, Kuroda, Reshamwala, Kunnas, Halmemies, Nakayama, Kilpeläinen, Ora, Kaseva, Hellström, Marjomäki, Karonen and Fukushima.)

Earlier studies have shown that the bark of Salix L. species (Salicaceae family) is rich in extractives, such as diverse bioactive phenolic compounds. However, we lack knowledge on the bioactive properties of the bark of willow species and clones adapted to the harsh climate conditions of the cool temperate zone. Therefore, the present study aimed to obtain information on the functional profiles of northern willow clones for the use of value-added bioactive solutions. Of the 16 willow clones studied here, 12 were examples of widely distributed native Finnish willow species, including dark-leaved willow ( S. myrsinifolia Salisb.) and tea-leaved willow ( S. phylicifolia L.) (3 + 4 clones, respectively) and their natural and artificial hybrids (3 + 2 clones, respectively). The four remaining clones were commercial willow varieties from the Swedish willow breeding program. Hot water extraction of bark under mild conditions was carried out. Bioactivity assays were used to screen antiviral, antibacterial, antifungal, yeasticidal, and antioxidant activities, as well as the total phenolic content of the extracts. Additionally, we introduce a fast and less labor-intensive steam-debarking method for Salix spp. feedstocks. Clonal variation was observed in the antioxidant properties of the bark extracts of the 16 Salix spp. clones. High antiviral activity against a non-enveloped enterovirus, coxsackievirus A9, was found, with no marked differences in efficacy between the native clones. All the clones also showed antibacterial activity against Staphylococcus aureus and Escherichia coli , whereas no antifungal ( Aspergillus brasiliensis ) or yeasticidal ( Candida albicans ) efficacy was detected. When grouping the clone extract results into Salix myrsinifolia , Salix phylicifolia , native hybrid, artificial hybrid, and commercial clones, there was a significant difference in the activities between S. phylicifolia clone extracts and commercial clone extracts in the favor of S. phylicifolia in the antibacterial and antioxidant tests. In some antioxidant tests, S. phylicifolia clone extracts were also significantly more active than artificial clone extracts. Additionally, S. myrsinifolia clone extracts showed significantly higher activities in some antioxidant tests than commercial clone extracts and artificial clone extracts. Nevertheless, the bark extracts of native Finnish willow clones showed high bioactivity. The obtained knowledge paves the way towards developing high value-added biochemicals and other functional solutions based on willow biorefinery approaches., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Tienaho, Reshamwala, Sarjala, Kilpeläinen, Liimatainen, Dou, Viherä-Aarnio, Linnakoski, Marjomäki and Jyske.)