Bioactive proteins have been detected in many different food sources. Beyond their nutritional value many of them exhibit functional effects both on the producing and on the consuming organisms. In recent years it has been recognized that proteins provide a rich source of biologically active peptides. The genus Solanum has a great variety of edible species that are an important source of protein. In this sense, some proteins might be involved in the response to wounding in plant defense mechanisms like patatine and solamarine and snakin 1 and 2 isolated from S. tuberosum tubers and cyphomine isolated from S. betaceum fruits. They have shown in vitro inhibitory action on hydrolases released by microorganisms involved in cell wall degradation during the invasion process. They also have in vitro inhibitory effect on phytopathogenic microorganism growth for both bacteria and fungi. It is thought that these proteins could be part of the so-called pathogenesis-related proteins. As they are also present in edible tissue, these proteins have been studied from a functional point of view. The purified proteins showed antioxidant or antiradical activities by a series of in vitro tests, including DPPH, ABTS, hydroxyl and superoxide radicals scavenging activity assays, anti-human low-density lipoprotein peroxidation tests, protections against hydroxyl radical-mediated DNA damages, peroxynitrite-mediated dihydrorhodamine 123 oxidations and b-carotene bleaching assay. A non mutagenic effect was observed in solamarine and cyphomine; solamarine also showed an antimutagenic effect against a direct mutagen. At present, an enzymatic hydrolysis process on proteins is being carried out in order to obtain smaller molecules (peptides and free amino acids) with improved nutritional quality and safety. Three bioactive peptides (5A, 5C and 6C) from potato protein hydrolysate fractions have recently been isolated and showed antioxidant activity. Hence, it would be possible to generate new products and carry out alternative applications for several agricultural and nutritional products.
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