Natural polyphenolic oligomers – proantocianidins (PAC) at the present moment are object of the intensivefundamental and applied investigations, due to unique structure and functionality of their macromolecules, which provide the broad possibility of the application of proantocoanidins in different areas: pharmacy, food industry, the production of the composite materials. PAC extractives (PACE) in significant amounts are present in the bark of different tree species, however this bark is burned as a cheap fuel not using its potential for obtaining of PACE and PAC. In the promotion work the potential of the bark of the widely spread in Latvia deciduous trees (white alder – Alnus incana, black alder – Alnus glutinosa, ash tree – Fraxinus excelsior and goat willow – Salix caprea) was evaluated as a source of the PAC and PACE, developing the regimes of the isolation of the PAC and PACE, as well as the possibilities of their application were evaluated, working out the innovative products in the context of the biorefiniery It was shown, that barks of grey alder and black alder are the best sources for extraction of PACE and obtaining of pure. The optimal extraction regimes established in the promotion work provide 87 % PAC from the bark to hydrophilic extract. The chemical composition of the hydrophilic extractives of the bark of the deciduous trees was investigated. It has been shown, that main components of extractives from the both alder barks and willow are polyphenols (about 50%), including 20–46% PAC, and glycosides, whereas the ash tree extract contains no PAC. The chemical structure of the PAC, isolated from the trees of alder species (Alnus incana and Alnus glutinosa) was clarified. The results of the TOF-MS and 13C-NMR have showed that they are the proantocianidins of the B-type, in which the monomeric units of catechin/epicatcehin are connected in oligomers with the degree of polymerization of 2–5 with C4–C8 bond. The high radical deactivation efficiency of PACE and PAC has been proven, allowing extracted substances to be used as antioxidants or as supplements in healthcare and disease prevention, antioxidants for polyurethane (PU) composite materials and foods containing lipids, as well as stabilizers in cosmetics. The functional composition of the PACE components ensures their effectiveness in the oxypropylation reaction, forming polyether polyols with relatively low viscosity, that facilitates the formation of the PU, as well as allows decreasing of the pressure in the spray system in the production of the PU foams. The new environmentally friendly adhesives on the basis of PACE for the production of the wood composite materials were offered. PACE, modified with polyethyleneamine, as wood environmentally friendly adhesive, has big potential in the production of particle boards for application in dry conditions, which fit to the requirements of the EN 312 P2 standard. The environmentally friendly binders, obtained by the partial replacement of the phenol-formaldehyde resins with modified PACE, were tested for the production of plywood. The testing of the bond strength have shown, that obtained plywood fit to the requirements of the standard LVS EN 314 point 5.1.3 and 5.1.1., for the use in the internal and external conditions. It was shown, that PACE can be successfully used for the partial replacement of the phenols in the syntheses of the phenol-formaldehyde resins. The replacement of the 20% of the oil-based phenols with PACE in the composition of the phenol-formaldehyde resins, causes the improvement of the mechanical properties of the plywood and reduction of the emission of the formaldehyde. The residue of deciduous bark after extraction can be used as a raw material for nano-filler, increasing the mechanical strength of softwood cellulose by 80 %, or as a solid biofuel due to its increased thermal capacity.