Bioactive peptides have been shown to exhibit a broad range of biological activities. These properties include antimicrobial, antioxidant, and antihypertensive activity, to name a few. These properties are of interest for both the food and pharmaceutical industries. They have the potential to be used in a variety of applications including sensory enhancement, sports and clinical nutrition, weight loss, mental health disorders, and the prevention and treatment of disease.
The antioxidant characteristics of peptides are primarily due to the amino acid sequence and structure. Histidine, glutamic acid, tryptophan, tyrosine, and cysteine are amino acids that possess strong antioxidant capabilities. They bind pro-oxidant metal ions, scavenge OH radicals, and inhibit lipid peroxidation (115). Tyr and His-containing peptides also display hydrogen-donating properties and are able to cleave disulfide bonds within the mitochondrial matrix, thus causing cell oxidation (122).
Peptides can be produced by chemical or solid-phase synthesis. Chemical synthesis in solution is a complex process that requires the use of fast coupling reagents and careful minimization of side reactions to ensure a quantitative formation of peptide bonding (Kent 1988). Solid-phase synthesis is a more rapid method that allows for larger scale production, utilizing a solid support that does not dissolve in the reaction mixture (Shigeri and others 2001).
The most commonly used test for assessing the antimicrobial activity of peptides is a broth microdilution assay. The test involves growing microorganisms in a well plate and adding various concentrations of the peptide to the growth medium. A peptide that does not inhibit bacterial growth will cause no turbidity to the well, and this can be measured by spectrophotometry (Otvos and Cudic 2007).