A Review of Recent Studies on the Antioxidant Activities of a Third-Millennium Food: Amaranthus spp.

Abstract

Amaranth (Amaranthus spp.) plant commonly refers to the sustainable food crop for the 21st century. The crop has witnessed significant attention in recent years due to its high nutritional value and agronomic advantages. It is a relatively well-balanced cosmopolitan food that is a protector against chronic diseases. Usually, the antioxidant activities of amaranth are held responsible for its defensive behavior. Antioxidant activity of plants, generally, is attributed to their phytochemical compounds. The current interest, however, lies in hydrolysates and bioactive peptides because of their numerous biological functions, including antioxidant effect. While the importance of bioactive peptides has been progressively recognized, an integrated review of recent studies on the antioxidant ability of amaranth species, especially their hydrolysates and peptides has not been generated. Hence, in this review, we summarize studies focused on the antioxidant capacity of amaranth renewal over the period 2015–2020. It starts with a background and overall image of the amaranth-related published reviews. The current research focusing on in vitro, in vivo, and chemical assays-based antioxidant activity of different amaranth species are addressed. Finally, the last segment includes the latest studies concerning free radical scavenging activity and metal chelation capacity of amaranth protein hydrolysates and bioactive peptides.

The Dual Nature of Amaranth—Functional Food and Potential Medicine

“…This should be clearly emphasized because it has a huge economic value due to the various benefits it can bring to producers, food processors, and consumers. Amaranth is a member of the Amaranthaceae family comprising about 70 species of annual plants [ 4 , 6 , 7 , 8 , 9 ]. In many countries, Amaranthus species are cultivated for use as cereals, vegetables, or ornamentals, a few species are considered weeds.…”

“…The main biological compounds found in amaranth are proteins, fats, carbohydrates, vitamins, and minerals [ 8 ]. The protein content (~18%) of amaranth seeds is higher than that of traditional cereals and varies according to the variety of the plant, the climate, and soil conditions and the method of fertilization [ 7 , 10 ].…”

“…Among the lipid fraction of amaranth, tocopherols, tocotrienols, and sterols play an important biological role [ 12 ]. Squalene has been identified in the seeds and leaves of the plant, and they are also very rich in vitamins (especially the B group) and minerals [ 8 ]. The percentage content of squalene in oil derived from amaranth is 2–8% [ 6 ] or 6–8% [ 5 , 13 ], depending on the source and author.…”

“…Amaranth seeds have a high nutritional value. The most important product obtained from amaranth is grain, which is a source of flour used in the baking industry [ 8 ]. Different plants such as millet, corn, sorghum, pseudocereals (amaranth), quinoa, and teff are the main components of a gluten diet [ 15 ].…”

New Mutant Amaranth Varieties as a Potential Source of Biologically Active Substances

“…Many studies confirm the antioxidant activity of extracts made from different parts of Amaranthus spp. [ 17 , 18 ]. Natural sources of antioxidants are primary plant phenolic compounds that may occur in all parts of plants, such as the fruits, vegetables, nuts, seeds, leaves, roots and bark [ 19 ].…”