Fractionation and identification of antioxidant and angiotensin-converting enzyme-inhibitory peptides obtained from plum (Prunus domestica L.) stones

• Highly antioxidant and ACE-inhibitory peptides were obtained from a plum by-product.
• Highest antioxidant capacity was observed in the whole Alcalase hydrolysate.
• Highest ACE-inhibitory capacity was observed in the <3 kDa Thermolysin fraction.
• RP-HPLC– and HILIC–MS/MS analyses afforded identification of most peptides.
• Antioxidant and ACE-inhibitory capacities were kept after gastrointestinal digestion.

Peptides with antioxidant and ACE-inhibitory capacities have been obtained from a plum processing by-product. The aim of this work was to fractionate most active plum hydrolysates, to identify peptides in these fractions, and to evaluate their resistance to gastrointestinal enzymes. Highest antioxidant capacity was observed in the whole Alcalase hydrolysate while peptides yielding the highest ability to inhibit ACE were concentrated in the fraction <3 kDa from the Thermolysin hydrolysate. RP-HPLC–ESI-MS/MS enabled the identification of 13 and 7 potential antioxidant and ACE inhibitory peptides, respectively, in these fractions. Nevertheless, RP-HPLC alone did not guarantee the successful separation of all peptides. The combination of RP-HPLC and hydrophilic interaction liquid chromatography (HILIC) coupled to ESI-Q-TOF-MS/MS enabled the identification of all peptides. Five potential antioxidant and three potential antihypertensive peptides could be additionally identified by HILIC. A total of 7 potential antioxidant peptides and 3 potential antihypertensive peptides resisted a simulated gastrointestinal digestion.