Integrated isopropanol/sodium citrate aqueous two-phase extraction and AB-8 macroporous resin purification of tea saponin from Camellia oleifera seed cake

Abstract Tea saponin was recovered from Camellia oleifera seed cake through an integrated process coupling isopropanol/trisodium citrate aqueous two-phase extraction with AB-8 macroporous resin purification. Extraction and purification parameters were optimized using Box–Behnken response surface methodology with triplicate validation experiments. The optimal extraction conditions: 1.30 g/10 mL trisodium citrate, 40 mesh particle size, 15:1 liquid-to-solid ratio, 77.4°C, and 32.8 min, under this condition, the yield reached up to 22.90% (RSD = 0.253%,value from predicted value = 0.02%). Purification at pH 6.1, 1.4 BV/h loading flow rate, and 3.9 BV of 75% ethanol with 92.21% purity (RSD = 0.191%, deviation from predicted value = 0.01%). Purified tea saponin scavenged DPPH radicals IC 50 = 0.42 mg/mL and hydroxyl radicals IC 50 = 0.56 mg/mL with a reducing power EC 50 of 0.22 mg/mL. AB-8 resin reached adsorption equilibrium within 6 h (equilibrium capacity 42.3 mg/g), enabling efficient batch processing. Integrating extraction and purification eliminated intermediate concentration steps, reducing product loss while maintaining antioxidant bioactivity.