Efficient extraction of polyphenols from bamboo shoot shells using deep eutectic solvents under optimized ultrasound-assisted conditions

Bamboo polyphenols are important bioactive substances possessing health-beneficial functions such as antioxidant and anti-tumour effects. Bamboo shoot shells, as processing by-products, contain high level of polyphenols which have not been utilized. This study developed and optimized an efficient and sustainable extraction method using ultrasound-assisted extraction (UAE) coupled with deep eutectic solvents (DESs) for the first time to recover polyphenols from Chimonobambusa purpurea shoot shells (CNSS). Six DES systems were initially screened based on polyphenol yield, with choline chloride–glycerol showing the best performance. Key extraction variables, including DES water content, solid-to-liquid ratio, ultrasonic temperature and extraction time, were examined. Optimal extraction conditions (solid-to-liquid ratio 1:39 g/mL, 20% DES water content, 43 °C, and 45 min) yielded 9.24 ±0.22 mg/g of polyphenols, closely aligning with the model-predicted value (9.37 ± 0.32 mg/g). Compared to ethanol extraction (4.54 ± 0.22 mg/g), the DES method improved yield by 103%. Antioxidant activity was evaluated using DPPH and ABTS radical scavenging assays, yielding IC₅₀ values of 1.78 mg/mL and 1.54 mg/mL, respectively. These results demonstrate the potential of this green extraction strategy to recover bamboo polyphenols efficiently and to promote the high-value utilization of bamboo shoot shells in functional food and nutraceutical applications. • Ultrasound-assisted DES extraction method was firstly explored for recovery of polyphenols from Chimonobambusa neopurpurea shoot shells. • Choline chloride–glycerol was identified as the most effective solvent in the screened DES systems. • Extraction process was optimized using Box–Behnken design, yielding 9.24 mg/g polyphenols under mild green conditions. • DES extraction improved polyphenol yield by 103% compared to conventional ethanol extraction. • Extracts exhibited strong antioxidant activity, highlighting potential in functional food applications.