Isolation, structural characterization and bioactivities of polysaccharides from Laminaria japonica: A review

•LJPs are mostly extracted with hot water and purified by DEAE.•LJPs mainly consist of β-(1 → 4)-GlcA, β-(1 → 6)-Glcp, α-(1 → 3,6)-Manp and α-(1 → 3)-Fuc.•Dose-effect and structure–activity relationships of LJPs need to be investigated.•LJPs can potentially be applied as an available adjunctive remedy. Laminaria japonica is a familiar marine plant and is often used as food due to its abundant carbohydrates, vitamins and minerals. As one of the main types of active substances in L. japonica, polysaccharides are widely used in the food and chemical industries and in medicine and healthcare due to their health benefits, such as immunoregulatory, antioxidant, and antidiabetic effects. However, there has been no systematic summary of the isolation, structural characterization and bioactivities of L. japonica polysaccharides (LJPs). Therefore, the present review includes a survey of extraction and purification methods for these bioactive molecules, along with a dissertation on the structural characterization of the carbohydrate components. Moreover, an overview of the most recent results related to LJP biological activities is provided. This review provides a useful reference for further research, production, and application of LJPs in functional foods and therapeutic agents.