Bioactive and protective polyphenolics from roots and stumps of conifer trees (Norway spruce and Scots pine)

The current era of bioeconomy strives to develop new, innovative products from natural raw materials in a sustainable way. In this PhD thesis, we have searched potential bioactive compounds from different parts of the neglected roots and stumps of conifer trees for high value products. Our aim was to establish deeper knowledge concerning chemical compositions of specified and defined biomass sources (roots and stumps of conifer trees) as well as the chemistry of certain natural polyphenolic compounds in different conditions.
Using methods of natural products chemistry, such as solvent extraction and chromatographic separation and analysis techniques (GC-MS, HPLC-DAD/MS), we found that the root bark of Norway spruce is a rich source of stilbenoid glucosides (astringin, isorhapontin and piceid). These have structural similarities with the most studied stilbenoid, resveratrol. We also found that the stumps of Scots pine are a source of stilbenoids, pinosylvin and its derivatives. Stilbenoids are bioactive compounds and they have shown a variety of beneficial activities in studies related for example to human health. They have also shown antimicrobial and protective properties in trees and also in tests against micro-organisms.
The highest concentrations of stilbenoid glucosides were found from the inner bark of the root zones closest to the stem of Norway spruce. This study also revealed that the root neck of Norway spruce is a new source of the bioactive lignan hydroxymatairesinol (HMR).
Chromatographic and spectroscopic methods were developed to isolate pure stilbenoids from the bark of Norway spruce roots for further experiments. The complete structural elucidation of stilbenoids from Norway spruce was performed by HPLC-DAD-NMR. The HPLC-DAD method was further optimized to isolate stilbenoids in a semipreparative scale.
The invividual stilbenoid molecules were isolated from the extracts and their photochemical stabilities (under fluorescent and UV light) were studied by HPLC-DAD, MS and NMR. Naturally-occurring trans stilbenoids undergo photochemical transformations to cis forms. However, the extended UV irradiation caused stilbenoids to form phenanthrene structures by intramolecular cyclisation. This is the first time that these new phenanthrene structures are reported to be derived from stilbenoids of spruce bark.
Our results show that that the roots and stumps of conifer trees contain bioactive polyphenolic compounds, such as stilbenoids and lignans. These molecules and the compounds formed thereof may have commercial value and the information gained would offer a base platform for the possible new commercial high-value products developed from forest biomass. Our study has also provided new scientific knowledge of natural compounds and their properties that may lead to new findings and deeper understanding of the physiology and internal protection processes of plants by their bioactive secondary metabolites.
Roots and stumps of conifer trees (Norway spruce and Scots pine) are a vast source of biomass containing potentially bioactive polyphenolic extractives as shown in this work, but this biomass is currently used for low-value energy production only. With already existing harvesting techniques, roots and stumps of conifer trees could be used as a source of commercially valuable biochemicals.