Antioxidant and ultraviolet shielding performance of lignin-polysaccharide complex isolated from spent coffee ground

Spent coffee ground (SCG) is a representative type of biomass waste with huge annual output. To better develop high value applications of SCG, in this study, the lignin-polysaccharide complex (LPC) was isolated from SCG by applying effective ball milling and the subsequent solvent extraction of 96 % 1, 4-dioxane aqueous solution. In addition to the comprehensive analyses of the obtained LPC regarding its chemical composition, surface morphology, molecular weight distribution, characteristic functional groups, surface chemical linkages, and thermal stability, its potentials in radical scavenging and UV shielding had been emphatically investigated. As revealed from the results, a proper duration (e.g., 4 h) of UV irradiation could evidently enhance the radical-scavenging capacity of LPC, ascribed to the increasing number of antioxidant groups. Moreover, the LPC-containing composite sunscreens also exhibited strengthened UV resistance after UV irradiation, which may benefit from the UV-induced conjugated structures and the π-π stacking of aromatic rings from both LPC and the active ingredients in commercial sunscreen. Therefore, LPC is highly promising to be exploited for the development of novel antioxidants and UV-shielding products, by virtue of its characteristic chemical structure and potential synergistic effect with other active ingredients from the composite.