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- Optimisation, by response surface methodology, of degree of hydrolysis and antioxidant and ACE-inhibitory activities of whey protein hydrolysates obtained with cardoon extractPublication . Tavares, T. G.; Contreras, M. M.; Amorim, M.; Martín-Álvarez, P. J.; Pintado, M. E.; Recio, I.; Malcata, F. X.The hydrolysis of bovine whey protein concentrate (WPC), alpha-lactalbumin (alpha-La) and caseinomacropeptide (CMP), by aqueous extracts of Cynara cardunculus, was optimized using response surface methodology. Degree of hydrolysis (DH), angiotensin-converting enzyme (ACE)-inhibitory activity and antioxidant activity were used as objective functions, and hydrolysis time and enzyme/substrate ratio as manipulated parameters. The model was statistically appropriate to describe ACE-inhibitory activity of hydrolysates from WPC and alpha-La, but not from CMP. Maximum DH was 18% and 9%, for WPC and alpha-La, respectively. 50% ACE-inhibition was produced by 105.4 (total fraction) and 25.6 mu g mL(-1) (<3 kDa fraction) for WPC, and 47.6 (total fraction) and 22.5 mu g mL(-1) (<3 kDa fraction) for alpha-La. Major peptides of fractions exhibiting ACE-inhibition were sequenced. The antioxidant activities of WPC and alpha-La were 0.96 +/- 0.08 and 1.12 +/- 0.13 mmol trolox equivalent per mg hydrolysed protein, respectively.
- Novel whey-derived peptides with inhibitory effect against angiotensin-converting enzyme: in vitro effect and stability to gastrointestinal enzymesPublication . Tavares, Tânia; Del Mar Contreras, Maria; Amorim, Manuela; Pintado, Manuela; Recio, Esidra; Malcata, F. XavierWhey protein concentrate (WPC) was subjected to enzymatic hydrolysis by proteases from the flowers of Cynara cardunculus, and the resulting angiotensin-converting enzyme (ACE)-inhibitory effect was monitored. The whole WPC hydrolysate exhibited an IC50 value of 52.9±2.9ºg/mL, whereas the associated peptide fraction with molecular weight below 3 kDa scored 23.6±1.1ºg/mL. The latter fraction was submitted to RP-HPLC, and 6 fractions were resolved that exhibited ACE-inhibitory effects. Among the various peptides found, a total of 14 were identified via sequencing with an ion-trap mass spectrometer. Eleven of these peptides were synthesized de novo – to validate their ACE-inhibitory effect, and also to ascertain their stability when exposed to simulated gastrointestinal digestion. Among them, three novel, highly potent peptides were found, corresponding to B-lactalbumin f(16–26) – with the sequence KGYGGVSLPEW, B-lactalbumin f(97–104) with DKVGINYW, and B-lactoglobulin f(33–42) with DAQSAPLRVY; their IC50 values were as low as 0.80±0.1, 25.2±1.0 and 13.0±1.0g/mL, respectively. None of them remained stable in the presence of gastrointestinal enzymes: they were partially, or even totally hydrolyzed to smaller peptides – yet the observed ACE-inhibitory effects were not severely affected for two of those peptides.