Bioactive Peptides in Donkey's Milk

Donkey’s milk (DM) is considered as a good alternative for children affected by cow’s milk protein intolerance (CMPA), when it is not possible breast feeding. DM This milk is very similar to human one, especially considering as regards to the similar lactose content, the low casein content and the similar mineral composition. As regards to the casein protein fraction, in DM are present mainly two types of caseins: beta and alpha s1- caseins whereas the alpha s2- and k-casein content resulted to be very low. The whey protein fraction of DM is characterized by the presence of proteins/peptides with potential nutraceutical function such as lysozyme, lactoferrin, lactoperoxidase, alpha-lactalbumin and beta-lactoglobulin. Lysozyme (14.4 kDa), is a well know enzyme with antimicrobial properties since it is able to hydrolyze the glyosidic bonds of mucopolysaccarides of the bacterial cell walls. DM lysozyme content (1.0 g/l) is much higher if compared to that one found in bovine (traces), human (0.12 g/l) and goat's milk (traces). Lysozyme may have therapeutic, antiviral and anti-inflammatory properties, therefore may help to reduce the incidence of gastrointestinal infections in the infants. Lactoferrin and lactoperoxidase (0.084 g/l and 0.11 mg/l in DM, respectively) are other two proteins that exhibit several activities. In particular, lactoferrin is an iron binding protein involved in regulation of iron homeostasis, cellular growth, anti-microbial and anti-viral functions and protection against cancer development and metastasis. Furthermore lactoferrin may have a prebiotic activity, stimulating the growth of beneficial bacteria in the intestinal tract. alpha-lactalbumin (about 12.0 kDa), is a whey protein with good nutritional value since it provides all essential and branched-chain amino acids to the growing infant, it is able to bind divalent cations facilitating the absorption of essential mineral. In conclusion, DM donkey’s milk possesses a set of nutritional properties especially thanks to the presence of bioactive peptides which have a high nutritional value.