Effect of simulated gastrointestinal digestion of bioactive peptide from pigeon pea (Cajanus cajan) tempe on angiotensin-I converting enzyme inhibitory activity

Purpose The purpose of this paper is to understand the effect of hydrolysis by pepsin and pancreatin on the angiotensin-I-converting enzyme (ACE) inhibitory activity of bioactive peptide from pigeon pea tempe and the absorption of pigeon pea tempe peptide by using the everted gut sac method. Design/methodology/approach The tempe was prepared by inoculating Raprima (Rhizopus oligosporus) on hulled-cooked pigeon pea for 48 h. The extraction was performed using the ultrasonic method at 40 kHz frequency and 100% ultrasonic power for 10 min. The extracted protein was placed in simulated gastrointestinal digestion using consecutive pepsin-pancreatin for 240 min. The hydrolysates were fractionated using a dialysis tube, and its absorption was assessed using the everted Sprague-Dawley rat gut sac. Findings The tempe protein from the hydrolyzed pigeon pea exhibited higher ACE inhibitory (71.53%) activity than that from the boiled pigeon pea (53.04%) (p = 0.028). The bioactive peptide of the digested pigeon pea tempe consisted of low-molecular-weight peptides (<1 kDa). The fraction also showed the highest ACE inhibition activity among the others (IC50 = 0.61 mg/mL, p = 0.021). Bioactive peptides from pigeon pea tempe were absorbed well in the small intestine, mainly in the jejunum. The activity of the absorbed peptides did not change considerably. Originality/value The activity of bioactive peptide of pigeon pea tempe was comparatively stable during digestion. It exhibited activity even after absorption in the small intestine. Thus, pigeon pea tempe can serve as an antihypertensive peptide source and alternative food for maintaining/reducing blood pressure.