Tryptophan Released From Mother's Milk Has Antioxidant Properties

Abstract

Bioactive factors in human milk (HM) are crucial to the health of newborns, especially preterm infants. These compounds assist in reducing the oxidative stress that may occur as a result of combined exposure to supplemental oxygen and immature physiologic defenses. To identify the components in HM that contribute to its greater resistance to oxidative stress compared with infant formulae, enzymatic hydrolysates of HM were prepared, ultrafiltered, separated, and analyzed for antioxidant potential. The antioxidant activity [M Trolox equivalent (TE/g)] of nondigested milk, whole digested milk, and derived ultrafiltrates were 80.4 Ϯ 13.3, 159.0 Ϯ 5.6, and 127.4 Ϯ 3.1, respectively. An HPLC fraction denoted as fraction 23 (5274 Ϯ 630 M TE/g) was obtained and its constituents identified as tryptophan (Trp), peptides HNPI, and PLAPQA. Scavenging activity was not observed for PLAPQA, whereas moderate activity was associated with HNPI (144 Ϯ 10.7 M TE/g) and very high activity to Trp (7986 Ϯ 468 M TE/g). Trp addition to HM and two infant formulas significantly increased formulae antioxidant properties. Trp appeared to be a powerful free radical scavenger naturally present in HM. Its antioxidant effects and potential application in the diets of infants, particularly preterm, must be examined further. (Pediatr Res 66: 614-618, 2009)

Tryptophan-containing milk protein-derived dipeptides inhibit xanthine oxidase

“…XO inhibition in the 40 % ACN fraction was higher than that of GLF-240 min hydrolyzate, suggesting that a more potent fraction has been isolated with activated carbon. Previous studies have demonstrated the antioxidant potential of Trp and a Trp rich fraction from human mother's milk in vitro [84]. However, these results did not translate in a similar effect in a cell culture model of Caco 2 cells, showing a prooxidant activity of Trp and the Trp rich fraction which was dose-dependent [20].…”

“…These results demonstrate that XO inhibition by the dipeptides was mainly due to the Trp residue. A Trp rich containing fraction from human mother's milk has previously been described for its antioxidant properties in vitro [84]. Certain amino acid structures have been correlated with high antioxidant properties.…”

“…However the mechanism of Trp described in this paper is different as it involves inhibition of an enzyme and not scavenging of free-radicals. Additional confirmation of in vivo XO inhibition with Trp, Val-Trp, Trp-Val and LF hydrolyzates is needed [84]. Food-grade hydrolyzates and dipeptides could have potential as a natural alternative to drugs for XO inhibition.…”

“…Different studies have demonstrated the anti-oxidative role of milk proteins and peptides [19,53,70,75,83]. A fraction from human milk enriched in Trp has been identified for its high scavenging activity in vitro [84]. However, when evaluated in a Caco-2 cell culture, this fraction or Trp itself behaved as a pro-oxidant [20].…”

Enhanced muscle nutrient content and flesh quality, resulting from tryptophan, is associated with anti-oxidative damage referred to the Nrf2 and TOR signalling factors in young grass carp (Ctenopharyngodon idella): Avoid tryptophan deficiency or excess

“…In mammals, oxidative tissue damage has been induced by excessive amounts of reactive oxygen species (ROS) (Kohen & Nyska, 2002). An in vitro study demonstrated that Trp inhibited the generation of ROS through the Fe(II)/CumOOH system (Tsopmo et al, 2009). These data suggest that Trp plays a role in inhibition of muscle oxidation and may therefore influence the flesh quality of fish; this potential role is worthy of investigation.…”