The Nutraceutical Properties of Ovotransferrin and Its Potential Utilization as a Functional Food
Ovotransferrin (Otrf) or conalbumin belongs to the family of transferrin iron-binding glycoproteins. In mammals, two different soluble iron-binding glycoproteins are present: (i) serum transferrin, involved in iron transport and delivery to cells and (ii) lactoferrin, involved in the so-called natural immunity. Differently, Otrf is the only soluble glycoprotein of the transferrin protein family present in avian. Otrf is present both in avian plasma and egg white and possesses both iron-transfer and protective properties [1 ]. Otrf represents about 12%–13% of total egg white proteins and contributes to promoting the growth and development of the chicken embryo mainly preventing the growth of micro-organisms together with other proteins such as lysozyme [2 ], cystatin [3 ,4 ], ovomacroglobulin [5 ] and avidin [6 ]. Galliformes (chicken, Gallus gallus and turkey, Meleagris gallopavo ) appear to possess albumens with greater antimicrobial activity than those of the anseriformes (duck, Anas platyrhynchos ), possibly due to higher concentrations of ovotransferrin and of the broad active c-type lysozyme [7 ]. However, recent evidence indicates that Otrf is endowed not only with the antibacterial activity related to iron withholding, but also with other roles related to the protection of the growing embryo, including: regulation of iron absorption; immune response; and anti-bacterial, anti-viral and anti-inflammatory properties. Some of these properties are shared by both the human protein homologues and peptides deriving from its partial enzymatic hydrolysis [8 ], being in this latter case also increased. The state of the art hereby described suggests that Otrf and its peptides can be used as functional food ingredients and as important components for nutraceuticals, being characterized both by protective functions and by substantial nutritional benefits; for these reasons, the utilization of Otrf and its peptides in functional foods can present several additional advantages over other natural compounds.