Insight on structure-property relationships of carrageenan from marine red algal: A review

[Display omitted] •Biological properties of CRG polysaccharides vary with their chemical structures.•The variety of monosaccharides and substituents lead to CRG derivatives’ diversity.•Chemical modification of CRGs generally appears at C-6 and/or C-2 of G4S units.•It is imperative to establish a certain acceptable daily intake of CRGs. Carrageenan (CRG) is a kind of linear sulfated polysaccharide that emerging as a promising substituent in food, pharmaceutics, and cosmetics. In recent years, biological properties of CRG polysaccharides such as antiviral, immunomodulatory, anticoagulant, antioxidant, and anticancer have been broadly studied, however, systematical summary of their structure-property relationships is scarce. Moreover, chemical modification is of great significance to explore biological and physiochemical properties of CRG polysaccharides which should be focused on. Chemical modification of CRG polysaccharides, e.g., carboxymethylation, thiolation, acetylation, phosphorylation, oversulfation, oxidization, and cationic or other derivatives, can improve their bioactivities and facilitate their applications in different biological systems. Hence, this review aims to elucidate structure-property relationships of CRG and its chemically modified derivatives with different structures and bioactivities, so as toxicity of CRG as food additive for the guidance of its clinical application.