A Cascade Approach to Valorizing Camellia oleifera Abel Shell: Ultrasound-Assisted Extraction Coupled with Resin Purification for High-Efficiency Production of Multifunctional Polyphenols

<i>Camellia oleifera</i> Abel shell is an abundant lignocellulosic byproduct of the Chinese woody oil industry, which is currently underutilized. To achieve its high-value utilization, this study developed an innovative cascade process integrating ultrasound-assisted extraction and macroporous resin purification for the efficient preparation of purified polyphenols from the shell (P-CPCS). The major constituents were identified by quadrupole/Orbitrap high-resolution mass spectrometry (HPLC-Q-Exactive-MS: Biotech Pack Co., Ltd., Beijing, China) analysis. The optimized process significantly enhanced the polyphenol yield (40.05 ± 0.58 mg GAE/g dw) and purity (57.72%), surpassing conventional methods. P-CPCS exhibited exceptional multifunctional bioactivities, including potent antioxidant capacity (with low IC₅₀ values against DPPH, ABTS⁺·, and ·OH radicals), effective tyrosinase inhibition (whitening effect), and significant bacteriostatic effects against various pathogens. Furthermore, P-CPCS notably suppressed the LPS-induced inflammatory response in RAW264.7 macrophages by reducing NO overproduction. This work highlights a novel and efficient strategy for upcycling agricultural waste into a high-performance natural antioxidant, positioning P-CPCS as a promising ingredient for applications in functional foods, cosmetics, and biomaterial stabilization.