Research progress in the preparation, structural characterization, bioactivities, and potential applications of sulfated agarans from the genus Gracilaria

Abstract

The genus Gracilaria produces 80% of the world's industrial agar. Agar of this genus is a promising biologically active polymer, which has been used in the human diet and folk medicine, alternative for weight loss, treatment of diarrhea, etc. With more attention paid to the genus Gracilaria‐sulfated agarans (GSAs), they exhibited multitudinous health benefits in antioxidant, antiviral, antibacterial, prebiotics, anti‐tumor, anticoagulant, and antidiabetic. Various preparation procedures of GSAs making the diversities of structure and biological activity. Therefore, this review summarized the isolation, identification, bioactivity potentials, and applications of GSAs, providing a reference to the development of GSAs in functional food and pharmaceutical industry. Practical applications The genus Gracilaria is known as a raw material for agar extraction. GSAs are food‐grade agaran with the properties of thermoreversible gels at low concentrations, which are commonly used as an additive for making candies as well as raw material for making soup and snacks. They are used in folk medicine to treat diarrhea and other diseases. As an important bioactive macromolecule, GSAs have various biological activities (such as antioxidant, antiviral, antibacterial, probiotic, anti‐tumor, anticoagulant, and antidiabetic activities), and have the potential to be developed as functional food and medicine. They could also be used to create innovative agar‐based products such as antibacterial films and drug carriers.

Laboratory horror stories: Poison in the agars

“…Similarly, the manufacture of the agar is decentralized, with many producers and distributors. More fundamentally, the quality of agar is affected by high heterogeneity of numerous factors, including species, growing environments, harvesting and extraction methods, post-extraction treatments, complexity of carbohydrates, their diverse modifications, and contaminants such as fatty acids, phycobiliproteins, pigments, and secondary metabolites [see ( Li & Liu, 2022 ) and refs therein]. And while vendors of scientific agar seek to remove factors that can inhibit microbial growth, the manufacturing processes are proprietary (i.e., opaque), the vendors do not reveal key variables such as species source, and detailed quality control measures are typically not provided to end-users.…”

Evaluating the Prebiotic Properties of Agar Oligosaccharides Obtained from the Red Alga Gracilaria fisheri via Enzymatic Hydrolysis

“…is a red alga found worldwide and is commonly used as the main raw material (80%) in the agar industry, followed by Gelidium spp. (20%) [20,21]. Gracilaria fisheri is widespread in Southern Thailand and has previously been described as abundant.…”