Citric-acid-assisted upcycling of Sparassis latifolia pseudosclerotia into thermoreversible polysaccharide hydrogels: Structure-property relationships and antioxidant activity in vitro and in vivo.

Sparassis latifolia pseudosclerotia represent a significant, underutilized fungal bioresource typically discarded during commercial mushroom production cycles. To upcycle this biomass, a sustainable citric-acid-assisted route transformed its extracted polysaccharides (1225 kDa; 9.74% uronic acid) into highly transparent, thermoreversible hydrogels. Rheological analysis confirmed an elastic response (G' > G") with a macroscopic gel-to-sol transition at 80-90 °C. The hydrogel displayed an 89% water-holding capacity and 280% swelling ratio within 15 min, supported by an interconnected microstructural network. Mechanistically, physical crosslinking was driven by hydrogen bonding, hydrophobic association, and high-molecular-weight chain entanglement. The matrix exhibited measurable antioxidant-associated activity, achieving an 87.0% inhibition response in the hydroxyl-radical assay in vitro. In vivo, oral administration in mice significantly enhanced systemic redox status; high-dose intervention increased serum SOD and CAT activities by 50.1% and 114.1%, respectively, while reducing splenic malondialdehyde levels. These findings establish a basis for the further development of pseudosclerotial polysaccharides as functional food hydrocolloids.