Angiotensin I‐converting enzyme inhibitory peptides in skim milk fermented with Lactobacillus helveticus 130B4 from camel milk in Inner Mongolia,China

BACKGROUND: Angiotensin I‐converting enzyme (ACE) is a dipeptidyl carboxypeptidase associated with the regulation of blood pressure. ACE inhibition results in a lowering of blood pressure. Lactic acid bacteria are known to produce ACE inhibitors during fermentation. Fermented camel milk is the main traditionally fermented dairy food for desert nomads. The beneficial effects of fermented camel milk, which include the prevention of such diseases and conditions as gastroenteritis, tuberculosis and hypertension, have been demonstrated experimentally. RESULTS: ACE inhibitory activity was observed in fermented milk containing Lactobacillus helveticus 130B4, a strain isolated from traditionally fermented camel milk. The peptide that inhibited ACE was purified from the fermented milk by reverse‐phase high‐performance liquid chromatography. The amino acid sequence of the peptide was identified as Ala‐Ile‐Pro‐Pro‐Lys‐Lys‐Asn‐Gln‐Asp (IC₅₀ = 19.9 µmol L^?1). The same Ala‐Ile‐Pro‐Pro‐Lys‐Lys‐Asn‐Gln‐Asp sequence was found in κ‐casein (κ‐CN) f107–115 from milk. The inhibitory activity of this nonapeptide (κ‐CN f107–115) was almost preserved even after successive digestion with pepsin, trypsin and chymotrypsin. Furthermore, the inhibitory activity of the purified peptide was completely preserved after heat treatment at 100 °C for 20 min. CONCLUSION: The fermented milk prepared with Lactobacillus helveticus 130B4 contained an ACE inhibitory peptide, κ‐CN 107–115. This fermented milk was expected to have anti‐hypertensive effect after ingestion because the peptide was stable to digestive protease and heat treatment in vitro. Copyright © 2008 Society of Chemical Industry     

Grass carp peptides hydrolysed by the combination of Alcalase and Neutrase: Angiotensin‐I converting enzyme (ACE) inhibitory activity,antioxidant activities and physicochemical profiles

In this study, grass carp peptides were prepared by enzymatic hydrolysis of grass carp protein using the combination of Alcalase and Neutrase, and angiotensin‐I converting enzyme (ACE) inhibitory activity in vitro, antihypertensive activity in vivo, antioxidant activities, and physicochemical properties of peptides achieved from grass carp protein were characterised after ultrafiltration and desalted processes using mixed ion exchange resins. The purified peptides exhibited strong ACE inhibitory activity (IC₅₀ = 105 μg mL^?1), antihypertensive activity with the maximal drop for systolic blood pressure (SBP) of 43 mmHg at a dosage of 100 mg per kg body weight in spontaneously hypertensive rat (SHR), and antioxidant activities indicated by thiobarbituric acid‐reactive substance values in a liposome‐oxidising system, radical‐scavenging activity and chelation of metal ions (Fe²⁺). The molecular weight of peptides was <1000 Da. Compared to grass carp protein, the peptides separated from enzymatic hydrolysates possessed similar amino acid compositions, but contained higher concentrations of essential amino acids. Moreover, the peptides exhibited excellent solubility at a wide range of pH values from 2 to 10, and lower apparent viscosity than the protein. The peptides separated from enzymatic hydrolysates might be used as a promising ingredient in antihypertensive functional foods and nutraceuticals.     

Recent advances in γ‐aminobutyric acid (GABA) properties in pulses: an overview

Beans, peas, and lentils are all types of pulses that are extensively used as foods around the world due to their beneficial effects on human health including their low glycaemic index, cholesterol lowering effects, ability to decrease the risk of heart diseases and their protective effects against some cancers. These health benefits are a result of their components such as bioactive proteins, dietary fibre, slowly digested starches, minerals and vitamins, and bioactive compounds. Among these bioactive compounds, γ‐aminobutyric acid (GABA), a non‐proteinogenic amino acid with numerous reported health benefits (e.g. anti‐diabetic and hypotensive effects, depression and anxiety reduction) is of particular interest. GABA is primarily synthesised in plant tissues by the decarboxylation of l ‐glutamic acid in the presence of glutamate decarboxylase (GAD). It is widely reported that during various processes including enzymatic treatment, gaseous treatment (e.g. with carbon dioxide), and fermentation (with lactic acid bacteria), GABA content increases in the plant matrix. The objective of this review paper is to highlight the current state of knowledge on the occurrence of GABA in pulses with special focus on mechanisms by which GABA levels are increased and the analytical extraction and estimation methods for this bioactive phytochemical. © 2017 Society of Chemical Industry     

Accumulating mechanism of γ‐aminobutyric acid in soybean (Glycine max L.) during germination

γ‐aminobutyric acid (GABA) has been found accumulating significantly in soybean seeds during germination. However, the mechanism of the accumulating process is not clear. Therefore, gene expression, enzyme activity and metabolites associated with GABA shunt in ZH 13 soybean during germination were analysed in this paper. GABA content in 5‐day germinated soybean was 0.26 ± 0.016 mg g^?1 DW, which was equivalent to six times concentration of original soybean. The GAD activity has a positive effect on the accumulation of GABA, as well as the GABA‐T activity was found to play a significant role in the degradation of GABA. The expression levels of GmGAD and GmGABA‐T may affect the GABA content by regulating the respective enzyme activities. In conclusion, upregulation of GAD and downregulation of GABA‐T may cause the accumulation of GABA.     

Selection of γ‐aminobutyric acid‐producing lactic acid bacteria and their potential as probiotics for use as starter cultures in Thai fermented sausages (Nham)

To produce a novel product of Thai fermented meats, such as healthy Nham, 602 lactic acid bacteria were isolated from fermented foods and fourteen isolates that produced high amounts of γ‐aminobutyric acid (GABA) were also tested for inhibiting the seven foodborne bacteria. Four selected isolates produced GABA in the range of 7339–9060 mg L^?1 (NH2 < NH102 < NH116 < HN8) and their culture filtrates with a pH of 3.8, except 4.2 for NH2 inhibited all target organisms. Selected strains were investigated for their physiological and functional properties of probiotics in vitro. Strain NH102 survived best in the gastrointestinal tract with only a one log cell decrease over 4 h, whereas strain NH116 was the best cholesterol removal (43%). None showed any haemolysis and all hydrolased bile salts. Strain NH2 was identified as Lactobacillus namurensis and all the others were Pediococcus pentosaceus. Strains HN8 and NH2 were potential starters for fermenting meats.     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

Effect of enzyme type and hydrolysis conditions on the in vitro angiotensin I‐converting enzyme inhibitory activity and ash content of hydrolysed whey protein isolate

Removal of salts from protein hydrolysate mixture on large scale is very difficult and relatively inefficient. Selecting practical proteinase system and hydrolysis conditions for the production of whey protein isolate (WPI) enzymatic hydrolysates with high angiotensin I‐converting enzyme (ACE) inhibitory activity and low ash content is very useful. The effect of alcalase, neutrase, trypsin and their combined system, i.e. alcalase‐neutrase and trypsin‐neutrase, under two different hydrolysis conditions, i.e. pH‐controlled and pH‐spontaneous drop, on the formation of ACE‐inhibitory peptides and the characteristics of WPI hydrolysate was investigated. Results showed that the ACE‐inhibitory activity of WPI hydrolysate obtained with alcalase was significantly higher than that of its trypsin or neutrase hydrolysate obtained at the same hydrolysis time by both pH‐controlled and pH‐spontaneous drop method (P < 0.05). The WPI hydrolysate obtained after 3 h incubation with alcalase plus 2 h with neutrase under pH‐spontaneous drop condition possessed the highest ACE‐inhibitory activity of 54.30% and the lowest ash content of 2.95%. This is practical as a functional ingredient in the food industry because of its high ACE‐inhibitory capability, commercial availability in large supply of alcalase and neutrase and no needing for additional desalting process.     

Physicochemical properties,antioxidant activity and inhibition of α‐glucosidase of a novel fermented pepper (Capsiccum annuum L.) leaves‐based vinegar

The aim of this study was to utilise by‐product pepper leaves for vinegar production due to its nutritional value. Changes in physicochemical and functional properties in four main process from raw material (leaves) to lactic acid (juice), alcohol (wine) and acetic acid (vinegar) fermentations were evaluated and compared. Their nutritional compositions were significantly different and particularly the wine and vinegar had higher total phenol content and their expanded diversity than the juice and then leaves (P < 0.05). Difference in values for phenolic compound was highly correlated with their α‐glucosidase inhibitory (AGI) and antioxidant capacities in DPPH and superoxide radical scavenging and reducing power assays (r = 0.919–0.981); vinegar ≥ wine > juice > leaves. Especially, AGI activity was greatly enhanced depending on fermentation steps beyond expectation. Thus, these data confirm that pepper leaves is a good functional source and the vinegar fermentation improved the functionality in stages.     

Beneficial effect of yam on the amyloid β‐protein,monoamine oxidase B and cognitive deficit in mice with accelerated senescence

This study was designed to evaluate the effect of yam tuber material [Dioscorea alata L. var. purpurea (M.) Pouch.] on the amyloid β‐protein (Aβ) accumulation, monoamine oxidase (MAO) activity, cognitive ability and antioxidative defense system in senescence‐accelerated mice (SAMP8). Three‐month‐old male mice were fed with four different diets for 12 weeks: a casein diet (control group) and a casein diet supplemented with either 100, 200 or 400 g kg^?1 lyophilized yam. The results of the active shuttle avoidance test showed that the mice fed with the yam‐containing diets had significantly better learning and memory ability than the control group. All yam‐containing diet groups had lower Aβ levels and MAO B activities than the control, whereas the MAO A activity did not differ among the four diet groups. At the 400 g kg^?1 level, the yam‐containing diet group showed significantly lower concentration of thiobarbituric acid‐reactive substances (TBARS), higher total thiol level and superoxide dismutase (SOD) activity in the hippocampus than the control, but these values were not altered by the 100 and 200 g kg^?1 yam‐containing diet groups. The addition of 200 or 400 g kg^?1 yam also lowered the triglyceride levels but not the total cholesterol concentration. These results indicate that lyophilized yam could reduce brain Aβ accumulation, MAO B activity and cognitive deficits and promote the antioxidative defense system in SAMP8 mice. The improvements were in a dose‐dependent manner, possibly because the 400 g kg^?1 yam‐containing diet might contain more antioxidative phytochemicals. Copyright © 2006 Society of Chemical Industry