Valorization of Sea Buckthorn, Black Chokeberry, and Black Currant Branch Biomass as a Novel Source of Bioactive Oligomeric Proanthocyanidins

This study aimed to evaluate the potential of branches of black chokeberry, sea buckthorn, and black currant as raw materials for the development of pharmacologically active compounds, primarily oligomeric proanthocyanidins (OPCs), as they exhibit a broad spectrum of biological activities, including antioxidant, antimicrobial, anti-inflammatory, anticancer, etc. Branch biomass collected in spring and autumn of 2023-2025 was analyzed for its functional group profile and used for the isolation of OPCs with ethanol, an ethanol-water mixture (1:1, <i>v</i>/<i>v</i>), and an ethanol-acetone-water mixture (4:1:5, <i>v</i>/<i>v</i>/<i>v</i>). The highest yield of OPCs (up to 14% of DB) was achieved using the ethanol-acetone-water solvent mixture. Using LC-MS/MS, the OPC composition was analyzed and found to consist of dimers (<i>m</i>/<i>z</i> 577), trimers (<i>m</i>/<i>z</i> 865), and tetramers (<i>m</i>/<i>z</i> 1153). The maximum OPC content was observed in autumn samples. Mechanical pretreatment enhanced OPC accessibility by disrupting cell walls and increasing particle surface, facilitating release from the matrix and yielding up to 1.2-fold more OPCs than from untreated biomass. Quantification of 22 elements in the biomass by ICP-MS revealed low levels of toxic metals along with the presence of nutritionally relevant elements. Therefore, from a chemical safety perspective, biomass can be considered suitable for use as a source of OPCs.