Proteins from watermelon (Citrullus lanatus L.) seed were isolated using acid-induced precipitation method and then hydrolysed using pepsin, trypsin and alcalase. The hydrolysates were investigated for in vitro antioxidant and α-amylase inhibitory properties. The yield of peptic hydrolysis (68.9 ± 1.0%) was significantly higher than of tryptic (41.4 ± 1.1%) and alcalase (38.5 ± 0.5%) hydrolysis. Peptic hydrolysate showed the highest radical-scavenging ability whereas tryptic hydrolysate gave the highest reducing ability. In a concentrationdependent manner, the hydrolysates demonstrated potent α-amylase inhibitory ability with alcalase and tryptic hydrolysates exhibiting 86.0 ± 3.9 and 83.0 ± 3.5% α-amylase inhibition respectively (IC 50 0.149 to 0.234 mg mL -1). Kinetic analysis revealed that the three enzyme hydrolysates inhibited α-amylase activity via a non-competitive inhibition mechanism. The results therefore indicate that these multidirectional bioactivities of watermelon seed protein hydrolysates may serve as useful tools in the formulation of antidiabetic agents.

SummaryMoringa oleifera is a nutrient rich plant that has the potential to combat malnutrition problems in Africa. This study aims to investigate the effect of fortification using Moringa oleifera flower powder on the sensory and proximate attributes of fermented yellow maize and millet blend (Ogi). The formulation was grouped into seven blends in ratio 100:0:0, 70:30:0, 70:25:5, 70:20:10, 70:15:15, 70:10:20, 70:5:25 for maize, millet and Moringa oleifera flower powder (MOFP) respectively. Moringa oleifera flower was air-dried for 5days, milled and sieved to obtained fine powder. The fine powder was mixed thoroughly with fermented maize and millet, wet milled and sieved. The proximate composition of fermented yellow maize and millet (Ogi) fortified with Moringa oleifera flower powder showed an increase in crude protein, crude fibre, ash and fat with increase in the levels of Moringa oleifera flower powder and decrease in carbohydrate and moisture content. Moisture, protein, fibre, fat, ash and carbohydrate contents varied in the range 7.92-9.74%, 10.46 _ 16.06%, 2.31-4.13%, 2.90-4.07%, 1.23-1.93% and 66.45-73.25% respectively. Sensory evaluation shows that blend 6 (20% MOFP) compared favourably with the control. Also, nutritional analysis shows that blend 6 is favourable as weaning food. Therefore, blend 6 formulation can be used as alternative to the weaning foods to improve the nutritional status of children and help to curb protein malnutrition.

No abstract

In recent times, researchers have explored food derived peptides to circumvent the side effects of synthetic drugs. This study therefore examined the amino acid constituents, in vitro antioxidant activities, angiotensin-1-converting enzyme (ACE), α-glucosidase and α-amylase inhibition kinetics of protein hydrolysate obtained from the seed of Luffa cylindrica . The peptide yield by pepsin (16.93 ± 0.28%) and trypsin (13.20 ± 1.02%) were significantly lower than that of Alcalase (34.04 ± 1.96%). Alcalase hydrolysate however displayed the highest ferric reducing antioxidant capacity (FRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and H 2 O 2 scavenging activities (0.63%, 85.88% and 41.69% respectively), while the highest superoxide scavenging activity was shown by peptic hydrolysate (57.89%). The ACE inhibition by the hydrolysates with IC 50 of 0.32–0.93 mg/mL, increased as the concentration of the peptic hydrolysate increased with the highest ACE-inhibitory activity (74.99 ± 0.43%) at 1.2 mg/mL of peptic hydrolysate. Tryptic and Alcalase hydrloysates exhibited a strong α-amylase inhibition having 27.96 ± 0.06% and 36.36 ± 0.71% inhibitory capacity respectively with IC 50 of 1.02–3.31 mg/mL. Alcalase hydrolysates demonstrated the strongest inhibition (65.81 ± 1.95%), followed by tryptic hydrolysates (54.53 ± 0.52%) in a concentration-dependent inhibition of α-glucosidase (IC 50 , 0.48–0.80 mg/mL). Kinetic analysis showed that ACE-inhibition by different concentrations of Alcalase, pepsin and trypsin hydrolysates is uncompetitive, mixed-type and non-competitive respectively. α-Amylase was non-competitively inhibited while α-glucosidase was un-competitively inhibited by all the hydrolysates. The total amino acid concentration for Alcalase, trypsin and pepsin hydrolysates was 53.51g/100g, 75.40g/100g and 85.42g/100g of Luffa cylindrica seed protein hydrolysate respectively, with glutamate being the most concentrated essential amino acid in all the three hydrolysates. From these results, it can be deduced that Luffa cylindrica seed Alcalase and tryptic protein hydrolysates may play critical and indispensible role as bio-tools in diabetes and hypertension treatment.

No abstract

This study investigated the in vitro antihypertensive, antiradical and hydrogen peroxidescavenging properties of protein hydrolysates from Citrullus lanatus (watermelon) seed (CSPHs) obtained through enzymatic digestion. Proteins from watermelon seeds were isolated and enzymatically hydrolyzed with non-specific (alcalase), moderately specific (pepsin) and highly specific (trypsin) proteases, mimicking human gastrointestinal digestion. The hydrolysates were investigated for inhibitory property against angiotensin-I-converting enzyme (ACE) activity. Using N-[3-(2furyl)acryloyl]-L-phenylalanyl-glycyl-glycine as the substrate, CSPHs showed concentration-dependent ACE inhibition (IC 50 1.377-1.757 mg/mL) with peptic CSPH having the strongest ACE-inhibition followed by tryptic CSPH. Kinetic analysis revealed that peptic CSPH inhibited ACE activity in a mixedtype inhibition pattern while alcalase and tryptic CSPHs exhibited non-competitive inhibition mode. Peptic CSPH demonstrated the strongest DPPH radical-scavenging activity while tryptic CSPH showed the highest H 2 O 2-scavenging property. These results show that protein hydrolysates from watermelon seed possess bioactivities that could be exploited in the management of hypertension.

Several novel functional peptides have been successfully extracted from plant storage proteins. This study investigated the degree of hydrolysis, peptide yield, amino acid constituents, angiotensin converting enzyme (ACE), alpha amylase inhibitory and in vitro antioxidant activities of cashew (Anarcardium occidentale) nut proteins (CNP) hydrolysates (CNPHs). Cashew nut proteins (albumin and globulin) were hydrolysed using pancreatin, Alcalase and trypsin. The peptide yield and degree of hydrolysis (DH) of CNP by pancreatin (75.69 AE 0.84%; 37.39 AE 0.31) was significantly higher than those by Alcalase (61.67 AE 0.55%; 23.87 AE 0.23) and trypsin (43.33 AE 0.45%; 11 AE 0.15). The inhibition of ACE by albumin and globulin hydrolysates was concentration dependent. At 1.2 mg/mL, ACE-inhibitory activity of pancreatic cashew nut globulin (CNGH) hydrolysate (51.65 AE 1.2%) was significantly higher than those of Alcalase (34.603 AE 0.65%) and tryptic (29.92 AE 0.73%) CNGHs. Cashew nut albumin hydrolysate (CNAH) demonstrated concentration-dependent alpha-amylase inhibition (IC 50 0.17 AE 0.02-0.41 AE 0.021 mg/mL). The order of inhibition was tryptic > Alcalase > pancreatic CNAHs. The pancreatic hydrolysates of both albumin and globulin fractions displayed the highest DPPH antioxidant activity, while pancreatic CNAH was the most potent superoxide anion scavenger. These findings therefore posit that cashew nut globulin and albumin hydrolysates are laden with useful bioactive peptides that may be further explored for regulation of blood pressure and sugar in hypertensive and diabetic in vivo models.

The interactions of Mg 2+ and Zn 2+ ions in the activation of non-specific tissue alkaline phosphatase were investigated using crude extracts of rat kidney. Activation of alkaline phosphatase by the metal ions was accompanied by changes in the kinetic parameters of p- INTRODUCTIONThe roles of metal ions in metalloenzymes include direct participation in catalysis, stabilization of protein structure and regulation of enzymatic activity. Membrane alkaline phosphatase (ALP) is a metal-containing enzyme that serves as a good model for the study of metal ion interactions in enzyme catalysis. Native E. coli ALP contains three metal ion binding sites (two Zn 2+ sites and one Mg 2+ site), and studies on their roles and interrelationships have provided some insights into the mechanism of the enzyme 1 . E. coli ALP is a zinc metalloenzyme, which can be activated by magnesium ion 2 . Removal of the Zn 2+ leads to loss of catalytic activity while its replacement by other divalent cations (Mn 2+ , Co 3+ , Cd 2+ , and Cu 2+ ) resulted in lower maximal activity 2 . It has been shown that while low concentrations of Mg 2+ stimulated the refolding of E. coli ALP, high concentration actually inhibited its reconstitution into the active form 3 . This suggests that Mg 2+ mediates stabilization and destabilization of the catalytically active structure of ALP at low and high concentrations respectively 4,5 . In E. coli ALP, Mg 2+ is thought to have a regulatory effect on the expression of catalytic activity and maintenance of structural integrity of the enzyme 1 . The specific binding of Mg 2+ to apo-ALP depends on both pH and the cooperative effects of Zn 2+ binding. Mg 2+ alone does not confer catalytic activity on ALP, but it does regulate the Zn 2+ -induced restoration of activity and perhaps, structural integrity of the metal-binding loci 1,6 .