Angiotensin-I-converting enzyme inhibitory, antimicrobial, and antioxidant effect of bioactive peptides obtained from different varieties of common beans (Phaseolus vulgaris L.) with in vivo antihypertensive activity in spontaneously hypertensive rats

Peptides obtained from three varieties of common beans (Phaseolus vulgaris L.) named plus black (PB), azufrado higuera (AH) and pinto Saltillo (PS) presented antimicrobial, antioxidant and antihypertensive activities. Peptides were obtained from these common beans protein concentrates after treatment with Alcalase(A (R)) followed by ultrafiltration using 1-, 3- and 10-kDa molecular weight cutoff membranes. Antioxidant activity was determined by the 2,2'-azino-bis (3-etilbenzotiazolin-6-sulfonic) acid method and was expressed as Trolox equivalent antioxidant capacity (TEAC). The highest antioxidant activity (630, 550 and 517 mM TEAC/mg protein) was observed in the group of peptides with a molecular weight lower than 1 kDa (F < 1) from PB, AH and PS bean varieties, respectively. Antibacterial activity was determined as susceptibility test in which ten of twelve bacteria strains showed growth inhibition with the total hydrolysates (TH) and the peptidic fraction 3-10 kDa; subsequently, the minimum inhibitory concentration was determined with the standard microdilution assay in a 96-well plates in which the peptidic fraction F < 1 kDa presented antimicrobial activity against Shigella dysenteriae with the three beans varieties at 0.1, 0.4 and 0.3 mg/mL (for PB, AH and PS, respectively). Additionally to the antimicrobial and antioxidant activities, the TH of the PB and AH bean varieties presented high inhibition of the angiotensin-I-converting enzyme (ACE-I) (IC50 = 4.34 +/- A 0.29 and 4.82 +/- A 1.59 mu g/mL, respectively). And, when the peptidic fraction F3-10 kDa was tested, the AH variety showed a significant increase in the ACE-I capacity (IC50 = 1.09 +/- A 0.04 mu g/mL). Importantly, this peptidic fraction decreased the systolic blood pressure in a spontaneously hypertensive rat model after 2 h of administration by a single interperitoneally dose.