The structural characteristic of bamboo shoot shell polysaccharides extracted using ultrasound‐assisted phosphotungstic acid hydrolysis and its protection against cell oxidative injury

Summary In this study, crude polysaccharide (BSSP) was extracted from bamboo ( Phyllostachys edulis ) shoot shell using the ultrasonic‐assisted phosphotungstic acid hydrolysis method. Then, BSSP was further fractionated by DEAE Sepharose fast flow column and serial NaCl solution elutions to obtain two fractions, BSSP‐A and BSSP‐B. The results showed that the maximum yield of BSSP was 195.2 mg g −1 (19.52%) under optimised conditions. Structural analysis indicated that both BSSP‐A and BSSP‐B were heteropolysaccharides with α‐pyranoside bond structure and mainly consisted of xylose by scanning electronic microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermal characterisation and nuclear magnetic resonance spectroscopy. BSSP‐B showed a better protective effect than BSSP‐A against H 2 O 2 ‐induced oxidative injury in WRL‐68 cells by protecting the cell membrane structure, maintaining mitochondrial membrane potential and increasing intracellular antioxidant enzymes activities. Immunoblotting indicated that polysaccharides might up‐regulate the expression of antioxidant enzymes through the Keap1/Nrf2 signalling pathway and thus alleviate H 2 O 2 ‐induced cell injury. The findings of this study suggested that polysaccharides from bamboo shoot shell may act as potent antioxidants in functional food industries.