Peptides as Antioxidants
Antioxidant Activity of Proteins
Proteins have antioxidant functions, for instance, they hinder the oxidation of lipids by specific mechanisms, for example iron-binding proteins and antioxidant enzymes or other non-specific mechanisms. The activity of antioxidant proteins transpires through multiple interactions between the capability to remove free radicals, neutralize reactive oxygen species, reduce hydroperoxides, enzymatically eliminate specific oxidizers, chelate prooxidative transition metals, and alter the physical properties of food systems. Peptides are molecules made of proteins and are most promising as protein antioxidants, some peptides are molecules made of proteins and are most promising as protein antioxidants, some studies demonstrate that peptides compared with intact proteins have essentially higher activity (Elias, Kellerby, and Decker 2008).
Bioactive peptides are specific protein fragments that are made up of amino acids and they have many benefits on human body function. These amino acids are linked by peptide bonds and may exhibit hormone or drug-like activities. According to metabolic studies made in living organisms, peptides are known to have an essential role in human health (Singh, Vij, and Hati 2014). Peptides usually contain 2-20 amino acids and they are generally rich in hydrophobic amino acids (Chakrabarti, Guha, and Majumder 2018). Also, the positive effects of peptides on health (antimicrobial, antithrombotic, antihypertensive, opioid, immunomodulator, cholesterol-lowering, mineral binding, and antioxidative) have attracted the attention of scientists and many scientific studies have been conducted on the mechanisms and their implied roles of bioactive peptides in the interception and treatment of different diseases (Cicero, Fogacci, and Colletti 2017). For a bioactive peptide to be considered bioactive, it must provide a physiologically measurable biological effect. This also applies to other dietary components. Besides, these bioactive peptides have the potential to positively affect human health they can also have some side effects, for instance toxicity, allergenicity, and mutagenicity (Moller et al. 2008). When the relationship between the chemical structure and activity of a peptide is compared it cannot always be predicted, on the other hand, it is known that the activity of the peptide depends on its characteristics such as amino acid sequence, the chain length of the peptide, the amino acid type in N- and C-terminal and the polarity of the amino acids that make up the peptides (Li and Yu 2015).
Production of Bioactive Peptides
The use of bioactive peptides is of great interest, and many studies are being conducted in the food industry to find and utilize new peptide sequences from protein-rich products (Chakrabarti, Guha, and Majumder 2018). Vegetable, animal, and marine foods contain a large number of bioactive peptides, and they occur in enzymatic hydrolysis, fermentation, chemical hydrolysis, or the processes of gastrointestinal digestion, and consequently, bioactive peptides are formed by the extraction of these foods (Rutherfurd-Markwick 2012; Cicero, Fogacci, and Colletti 2017). Animal-based peptides can be obtained from meat proteins, eggs, and milk (whey and casein), and plant-based peptide plant sources are obtained from oats, soy, canola, wheat, legumes (chickpeas, beans, peas, and lentils), flaxseeds, and hemp seeds. Additionally, proteins from marine sources such as fish, salmon, squid, sea urchin, sea horse, oyster, and snow crab were also used (Kitts and Weiler 2003; Moller et al. 2008). The truth that peptides are inactive in the protein sequence is found as a result of enzymatic hydrolysis in vivo/in vitro (Hartmann and Meisel 2007; Sila and Bougatef 2016). The most common method of obtaining bioactive peptides is the hydrolysis of protein molecules with proteolytic. The efficiency and activity of bioactive peptides have an important place. The biological activity of the entire hydrolysate is evaluated and purified by enzymes and identified to find the most amino acid-strong sequence of bioactive peptides (Chakrabarti, Guha, and Majumder 2018). There are methods to estimate the yield of bioactive peptides from food protein sources. Frequently used methods are the quantitative structure-activity relationship (QSAR) and bioinformatics based in-silico methods (Gu, Majumder, and Wu 2011; Chakrabarti, Guha, and Majumder 2018). Proteins can be hydrolyzed to peptides with the proteolytic enzymes of bacteria. Hydrolysates can be developed into functional foods after in vivo testing for a biologically active hydrolysate (Daliri, Oh, and Lee 2017). The chemical synthesis of bioactive peptides is constantly increasing because the quantity of these peptides in nature is very low (Perez et al. 2012).
In enzyme hydrolysis proteins are treated with different enzymes at a given pH and temperature, and enzyme hydrology has some advantages. These advantages are that is has shorter reaction times compared to microbial fermentation and this method is easy to scale (Daliri, Oh, and Lee 2017).
The fermentation method is related to the cultivation of yeasts, fungi, bacterial microorganisms, and uses enzymes of microorganisms and hydrolyzes the protein to shorter peptides. Microorganisms must grow to use the fermentation method. Therefore, this method is much more temporary than enzyme hydrolysis. Extending hydrolysis relies on the microbial strain, protein source, and fermentation time (Chakrabarti, Guha, and Majumder 2018).