Impact of Different Extraction Methods on the Physicochemical Characteristics and Bioactivity of Polysaccharides from Baobab (Adansonia suarezensis) Fruit Pulp

Polysaccharides from baobab (Adansonia suarezensis) fruit pulp (ASPs) hold significant potential for pharmaceutical and functional food applications due to their bioactivities. This study systematically evaluated the effects of six extraction methods-hot water (ASP-HW), acid (ASP-AC), alkaline (ASP-AL), and their ultrasound-assisted counterparts (ASP-HWU, ASP-ACU, ASP-ALU)-on the yield, chemical composition, structural properties, and biological activities of ASPs. The results demonstrated that the extraction solvent critically influenced key properties: alkaline-based methods (ASP-AL, ASP-ALU) achieved the highest yields (up to 62.47%) and yielded polysaccharides with lower molecular weights (approximately 19,600-19,813 Da) and smaller particle sizes (around 140-147 nm). All ASPs were identified as acidic pectic polysaccharides, composed of galacturonic acid, xylose, galactose, and arabinose. Notably, ASP-AC, ASP-ACU, ASP-AL, and ASP-ALU exhibited a triple-helix conformation, which was absent in hot water-extracted polysaccharides. Bioactivity assessments revealed that ASP-AL and ASP-ALU possessed superior antioxidant capacities, demonstrating the lowest IC₅₀ values for DPPH radical scavenging (113.67-116.67 μg/mL) and ABTS radical scavenging (79.33-79.67 μg/mL), as well as potent α-glucosidase inhibitory activity (IC₅₀: 0.146-0.206 mg/mL), outperforming other extracts and the positive control acarbose. Correlation analysis indicated that enhanced bioactivity was associated with lower molecular weight and reduced uronic acid content. These findings underscore that alkaline extraction is an efficient strategy for obtaining highly bioactive polysaccharides from Adansonia suarezensis fruit pulp, providing a valuable theoretical foundation for their utilization in developing nutraceuticals and functional foods.