Sustainable valorization of Inonotus obliquus via temperature-gated natural deep eutectic solvents extraction: Polysaccharide-antioxidant partitioning.

Inonotus obliquus is a medicinal mushroom rich in bioactive metabolites, including polysaccharides and antioxidants, that provide notable nutritional and therapeutic benefits. However, conventional extraction techniques are hindered by low efficiency, thermal degradation of high-molecular-weight β-glucans, and poor retention of heat-sensitive antioxidants. To overcome these limitations, this study developed a temperature-gated natural deep eutectic solvents (NADESs) extraction strategy for Inonotus obliquus. Specifically, hydrophilic NADES based on choline chloride (ChCl)/polyol systems were optimized to enable temperature-controlled separation of polysaccharides and antioxidants. Among them, ethylene glycol-based with the optimized ChCl:EG:H2O NADES, polysaccharides were best obtained at 90 °C. Conversely, ultra-high temperatures (120-200 °C) switched the outcome toward antioxidants, despite caramelization beyond 180 °C. This tunability allowed for the selective recovery of either high-mass β-glucans at low temperatures or potent antioxidant-rich supernatants at 180 °C, with the latter involving partial degradation of β-glucans. Structural transitions under high-temperature conditions were further confirmed by FT-IR analysis. Overall, this study establishes a green and efficient temperature-gated NADES platform for the co-production of both preserved polysaccharides and potent antioxidants from Inonotus obliquus within a single system. This strategy enables the dual-target extraction of functionally distinct fractions and effectively overcomes the conventional trade-off between yield and thermal stability.