Oligosaccharides Derived from Red Seaweed: Production, Properties, and Potential Health and Cosmetic Applications

Abstract

Because of their potential use as functional ingredients in human nutrition, oligosaccharides derived from natural sources are receiving paramount consideration. Red seaweed, a proven rich source of agar and carrageenan, is one of the most abundantly present sources of such oligosaccharides. Agaro-oligosaccharides (AOS) and carrageenan-oligosaccharides (COS) are produced from agar and carrageenan, respectively, through chemical and enzymatic hydrolyses. Enzymatic hydrolysis of agar and carrageenan into oligosaccharides is preferred in industrial production because of certain problems associated with chemical hydrolysis, including the release of high amounts of monosaccharides and undesirable toxic products, such as furfural. AOS and COS possess many biological activities, including prebiotic, immuno-modulatory, anti-oxidant, and anti-tumor activities. These activities are related to their chemical structure, molecular weight, degree of polymerization, and the flexibility of the glycosidic linkages. Therefore, the structure⁻function relationship and the mechanisms occurring during the specific biological applications of AOS and COS are discussed herein. Moreover, the chromatographic separation, purification, and characterization of AOS and COS are also part of this review. This piece of writing strives to create a new perspective on the potential applications of AOS and COS in the functional food and pharmaceutical industry.

Keywords: agaro-oligosaccharides; biological activities; carrageenan-oligosaccharides; red seaweed.

Figure 1

Schematic structure of red seaweed oligosaccharides. (A) Agaro-oligosaccharide and neoagaro-oligosaccharides; (B) κ-carrageenan oligosaccharides; (C) ι-carrageenan oligosaccharides; and (D) λ-carrageenan oligosaccharides.

Figure 2

Schematic diagram of red seaweed oligosaccharides production, purification, analysis, and their resultant biological activities.

Figure 3

The purification of neoagaro-oligosaccharides by Sephadex LH-20 chromatography (100 × 1.6 cm). Distilled water was the elution phase and the fraction was detected by phenol-sulfuric acid method. The purity of the purified neoagaro-oligosaccharides (NAOS) was proved by thin layer chromatography (TLC) assay (inserted panel). The figure is from reference [23].

Figure 4

Representative MALDI-TOF/TOF MS of agaro-oligosaccharide (A) and neoagaro-oligosaccharide (B) prepared by acid hydrolysis of agarose. Figure is from reference [82].

Figure 5

Represent ¹H-NMR of (A) κ-carrageenan, (B) ι-carrageenan, and (C) λ-carrageenan in deuterium oxide. D: 4-linked α-galactopyranose; DA: 4-linked 3,6-anhydro-α-galactose; G: 3-linked β-d-galactopyranose. The figure is from reference [86].

Figure 6

Schematic representation of agaro-oligosaccharide and carrageenan-oligosaccharide as prebiotics and their activity in host immuno-modulation. IL: Interleukin; TNF-α: Tumor necrosis factor-α; TR: Toll-like receptor.