Enhancement of Norway spruce bark side-streams: Modification of bioactive and protective properties of stilbenoid-rich extracts by UVA-irradiation

Anna Liisa Välimaa, Jan Erik Raitanen, Jenni Tienaho, Tytti Sarjala, Eiko Nakayama, Risto Korpinen, Sari Mäkinen, Patrik Eklund, Stefan Willför, Tuula Jyske*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

21 Citations (Scopus)


Bark of Norway spruce (Picea abies [L.] Karst.) trees contains large amounts of polyphenolic stilbene glucosides. Stilbene-rich bark extracts could be utilized as e.g., preservatives due to their antioxidative, antifungal, and antibacterial properties. As stilbenes are photosensitive compounds, ultraviolet (UV) light induces a well-known intramolecular cyclization, leading to the formation of substituted phenanthrenes via a dihydro-phenanthrene intermediate. The possible UV-induced changes in the biological activities of the stilbene extracts remain, however, poorly known. Such information is crucial for practical application development. This study elucidated for the first time, how UVA-treatments of spruce bark extracts affect the chemical composition of the extracts, and further change their antimicrobial and antioxidative activities. Norway spruce inner bark was extracted (‘Extract’) and soluble mono- and disaccharides removed using Amberlite XADHP7 (‘Extract XAD’). These extracts were then treated with UVA-light (‘Extract UV’, ‘Extract XAD UV’), and chemical properties analyzed by GC–MS and HP-SEC. The antimicrobial activities of untreated and modified extracts against Staphylococcus aureus, Candida albicans, and Escherichia coli, were evaluated. Additionally, differences in the antioxidant activity between the untreated and UV-treated bark extracts were measured at a total stilbene concentration of 0.5 mg/mL EtOH, using the FRAP and ORAC methods. Also, antioxidant effects were evaluated in a liposome model to assess the ability of the extract to prevent lipid oxidation. Our novel results show that UVA-induced modification of the stilbene-rich inner bark extracts increased the radical scavenging activity. However, UVA-irradiation decreased the capacity of the extracts to prevent lipid oxidation in the liposome system method. The results also indicate a maintained or slightly increased antimicrobial activity after UVA-modification. This study shows that Norway spruce bark stilbenoids and the compounds formed by UVA-irradiation thereof show biological activity, and thus have commercial potential as e.g., preservatives.

Original languageEnglish
Article number112150
JournalIndustrial Crops and Products
Publication statusPublished - Mar 2020
MoE publication typeA1 Journal article-refereed


  • Antimicrobial
  • Antioxidant
  • Bark side-stream
  • Preservative use
  • Stilbenoids
  • UV-light


Dive into the research topics of 'Enhancement of Norway spruce bark side-streams: Modification of bioactive and protective properties of stilbenoid-rich extracts by UVA-irradiation'. Together they form a unique fingerprint.

Cite this