Abstract
Oxidative stress induces various cardiovascular, neurodegenerative, and cancer diseases, caused by excess reactive oxygen species (ROS). It is attributed to the lack of sufficient antioxidant defense capacity to eliminate unnecessary ROS. Seaweeds are largely cultivated for their edible and commercial purposes. Excessive proliferation of some seaweeds has occurred in coastal areas, causing environmental and economic disasters, and even threating human health. Removing and disposing of the excess seaweeds are costly and labor-intensive with few rewards. Therefore, improving the value of seaweeds utilizes this resource, but also deals with the accumulated biomass in the environment. Seaweed has been demonstrated to be a great source of polysaccharides antioxidants, which are effective in enhancing the antioxidant system in humans and animals. They have been reported to be a healthful method to prevent and/or reduce oxidative damage. Current studies indicate that they have a good potential for treating various diseases. Polysaccharides, the main components in seaweeds, are commonly used as industrial feedstock. They are readily extracted by aqueous and acetone solutions. This study attempts to review the current researches related to seaweed polysaccharides as an antioxidant. We discuss the main categories, their antioxidant abilities, their determinants, and their possible molecular mechanisms of action. This review proposes possible high-value ways to utilize seaweed resources.
Highlights
Reactive oxygen species (ROS) are byproducts of aerobic metabolism, mainly produced in the mitochondria
The radical scavenging capacity of seaweed polysaccharides have been evaluated by two categories of assays: hydrogen atom transfer (HAT) and electron transfer (ET) reaction-based assays, depending on particular reactions [12]
The assays of oxygen radical absorbance capacity (ORAC), 2,2’-azino-bis (3-ethylbenzothiazoline -6-sulphonic acid)(ABTS), superoxide anion (O2−), and hydroxyl (·OH) radicals scavenging activity are typically the HAT-based methods applied to measure the antioxidant ability of seaweed polysaccharides [80,87,88,89]
Summary
Reactive oxygen species (ROS) are byproducts of aerobic metabolism, mainly produced in the mitochondria. Antioxidants have been deemed as substances with the potential at a relatively low concentration to delay or prevent the oxidation of a target substrate They play the role of “free radical scavengers” by avoiding and repairing damage caused by oxidative stress. They enhance the immune system and decrease the risk of inflammation, cancer, aging, and hypertension [11,12,13]. Seaweeds are rich in polysaccharides, proteins, vitamins, and minerals, as well as a great variety of secondary metabolites with diverse biological functions [32] Due to their special structures, seaweed polysaccharides have been identified as being effective as antioxidants, immune-modulatory, anti-inflammatory, anti-coagulant, and anticancer agents [30,33,34,35,36]. The keywords, “polysaccharide*”, “seaweed” or “marine algae”, and “antioxidant” were searched in “Web of Science” and “Scopus”, for the period between 2000 and 2020
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