Sacha Inchi (Plukenetia volubilis L.) polysaccharides and related carbohydrate products: Extraction, structural diversity, bioactivities, structure–activity relationships, and sustainable valorization

Sacha Inchi (Plukenetia volubilis L.) is increasingly utilized for oil and protein production, whereas seed shells/testa, fruit husks/capsules, leaves, and oil-processing-derived co-products remain incompletely developed as carbohydrate resources. This review critically synthesizes current advances in the extraction, structural characteristics, biological activities, structure-activity relationships (SARs), and sustainable valorization of Sacha Inchi polysaccharides and related carbohydrate products. A material-centered framework is adopted to distinguish purified polysaccharides, crude polysaccharide preparations, chemically complex extracts, structural carbohydrates, and downstream oligosaccharides, while research maturity is evaluated according to chemical/structural resolution and biological validation depth. Hot-water extraction remains the best-validated route for recovering native Sacha Inchi polysaccharides; ultrasound-assisted extraction primarily offers process intensification, microwave-assisted evidence remains largely focused on phenolic-rich extracts, and enzymatic processing is better regarded as downstream carbohydrate conversion. Structurally characterized polysaccharides span an apparent molecular-weight range of approximately 17.7-144 kDa and display substantial diversity in monosaccharide composition, glycosidic architecture, branching, and higher-order organization. Purified PVLP-1 and shell-derived polysaccharides provide the clearest polysaccharide-specific chemical and cellular evidence, whereas crude SISP and carbohydrate-rich leaf preparations have reached animal-level validation but with lower carbohydrate-specific attribution. Shell-derived oligosaccharides further illustrate a direct conversion route from structural carbohydrates to candidate functional products. Current SAR evidence supports emerging structure-associated patterns and mechanistic hypotheses rather than a completed predictive model. Future progress requires standardized and traceable materials, controlled structural variation, integrated mechanistic and physiological validation, preparation-specific safety assessment, scalable processing, and system-level sustainability evaluation. Together, these advances could support the development of scientifically grounded functional ingredients and cascade-biorefinery strategies for more complete utilization of Sacha Inchi carbohydrate resources.