Unveiling the Structural Properties of Lignin–Carbohydrate Complexes in Bamboo Residues and Its Functionality as Antioxidants and Immunostimulants

Lignin–carbohydrate complexes (LCCs), a significant component of plant cell walls, have been found to bear biological functionality as antioxidants in food and as immunostimulants for living cell. In this work, a lignin-rich and a carbohydrate-rich LCCs preparations were isolated from bamboo residues (bamboo green and bamboo yellow). Each preparation was characterized by chemical composition and LCCs linkage types and quantities by high performance anion exchange chromatography (HPAEC) and NMR technologies (quantitative 13C NMR and 2D-HSQC NMR). Furthermore, evaluation of each LCCs preparation’s suitability as antioxidant and immunological substances were explored. Antioxidant assays indicated that all the LCCs preparations exhibited pronounced antioxidant activities for scavenging the 2,2-diphenyl-1-picryl-hydrazyl and hydroxyl radicals, while the lignin-rich LCCs outperformed the carbohydrate-rich LCCs. Immunological analysis showed that carbohydrate-rich LCCs could significantly inhibit the growth of breast tumor cells (MCF-7), while lignin-rich LCCs could stimulate the growth of macrophage cells (RAW 264.7). These results imply that LCCs extracted from bamboo may be used as novel and natural antioxidants or immunostimulants.