Facile extraction of lignin-carbohydrate complexes from bamboo with formic acid aqueous solution under moderate conditions

The extraction of lignin-carbohydrate complexes (LCC) while preserving the majority of the interconnecting bonds poses a formidable challenge in characterizing the structure and exploring further applications. In this study, a straightforward approach was proposed to extract LCC from bamboo by precisely adjusting formic acid aqueous solution concentrations (70 % to 100 %) and reaction temperatures (40 to 100 °C) under normal pressure. Notably, employing a 90 % formic acid aqueous solution at 100 °C for 2 h led to an impressive LCC yield of 24.47 %. Moreover, all the LCC samples demonstrated exceptional homogeneity with a polydispersity index ≤ 1.97. Nuclear magnetic resonance analysis revealed the presence of phenyl glycosidic, benzyl ether, benzyl ester, and acetal bonds within the extracted LCC, with phenyl glycosidic bonds serving as the predominant linkages. The LCC samples displayed notable antioxidant capacity, as evidenced by their high DPPH free radical scavenging index of 1.28.