No abstract

The aim of this work was to compare the antioxidant and angiotensin converting enzyme (ACE) inhibitory properties of Moringa oleifera seed protein isolate (ISO) and its enzymatic protein hydrolysates. ISO was subjected to enzymatic (alcalase, pepsin and trypsin) hydrolysis to obtain alcalase isolate, pepsin isolate and trypsin isolate hydrolysates (AIH, PIH, TIH). Amino acid composition was similar for the samples except that TIH had lower Sulphur-containing amino acids while PIH was lower in tryptophan. All the samples were tested for antioxidant properties through free radical scavenging abilities such as 2,2 diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assays as well as ferric reducing antioxidant power (FRAP) and metal ion chelation assays. The maximum percentage inhibition obtained for the samples from the different assays are: DPPH, 36% (PIH); FRAP, 0.04% (PIH); hydroxyl radical scavenging activity, 42.98% (ISO); and inhibition of metal ion chelation, 29.46% (AIH). AIH (79.3%) had the highest ACE-inhibitory activity followed by TIH (75.1%) while PIH (43.0%) had the least. Generally, the hydrolysis process produced hydrolysates with improved antioxidant and ACE-inhibitory properties when compared to the isolate. We conclude that enzymatic hydrolysis with alcalase, pepsin and trypsin may be used to produce M. oleifera seed protein hydrolysates with potential to be used as ingredients for the formulation of functional foods and nutraceuticals.

Moringa seed peptides were tested for antioxidant properties through free radical scavenging abilities (1,1‐diphenyl‐2‐picrylhydrazyl [DPPH] and hydroxyl radical scavenging assays [HRSAs]), inhibition of metal iron (ferric reducing antioxidant power [FRAP] and metal chelation tests) and in vitro antihypertensive properties through angiotensin converting enzyme (ACE) and renin inhibition tests. Compared to the hydrolysates, membrane fractionation led to improved antioxidative properties. Significant among the samples are <1 kDa (67.77%), 3–5 kDa (44.15%), 5–10 kDa (0.153 mmol Fe2+), and 3–5 kDa (11%) for DPPH, HRSAs, FRAP, and metal chelation ability, respectively. While there was a progressive increase in inhibition of the membrane fraction against ACE with the 5–10 kDa having significantly (p < 0.05) higher (73%) inhibition compared to other, there was no particular trend for the renin inhibition. However, the 5–10 kDa still showed better inhibition (57%) ability compared to others membrane fraction. We concluded that alcalase globulin hydrolysate and its membrane fractions possessed potent bioactive peptides. Practical applications Consumers more than ever before are getting concerned about the food they consume. This has resulted in the development and growth of functional foods. Functional foods are foods that are able to provide some physiological benefits such as antioxidative, antidiabetes, antihypertensive, and antiinflammatory among others besides their normal provision of nutrition. The growth of functional food market is due to the discovery of bioactive components in foods and viable opportunities still exist unexplored, especially with respect to the locally available and cheap underutilized crops such as Moringa oleifera seed. Plant‐derived antioxidants (such as bioactive peptides) have gained considerable importance due to their potential health benefits; also epidemiological studies have shown that consumption of plant foods is beneficial. This benefit could readily be provided by peptides from Moringa oleifera seed; a cheap and commonly available but underutilized crop.