Chemical Constituents of Gold‐red Apple and Their α‐Glucosidase Inhibitory Activities

Ten compounds were isolated and purified from the peels of gold‐red apple (Malus domestica) for the 1st time. The identified compounds are 3β, 20β‐dihydroxyursan‐28‐oic acid (1), 2α‐hydroxyoleanolic acid (2), euscaphic acid (3), 3‐O‐p‐coumaroyl tormentic acid (4), ursolic acid (5), 2α‐hydroxyursolic acid (6), oleanolic acid (7), betulinic acid (8), linolic acid (9), and α‐linolenic acid (10). Their structures were determined by interpreting their nuclear magnetic resonance and mass spectrometry (MS) spectra, and by comparison with literature data. Compound 1 is new, and compound 2 is herein reported for the 1st time for the genus Malus. α‐Glucosidase inhibition assay revealed 6 of the triterpenoid isolates as remarkable α‐glucosidase inhibitors, with betulinic acid showing the strongest inhibition (IC₅₀ = 15.19 μM). Ultra‐performance liquid chromatography‐electrospray ionization MS analysis of the fruit peels, pomace, flesh, and juice revealed that the peels and pomace contained high levels of triterpenes, suggesting that wastes from the fruit juice industry could serve as rich sources of bioactive triterpenes.     

Total Phenol Content,Antioxidant Activities and α‐Glucosidase Inhibition of Sesame Cake Extracts

Sesame cake, the byproduct obtained after the removal of oil is presently used as cattle field. Present study evaluates the α‐glucosidase, α‐amylase inhibition and antioxidant properties of black sesame cake extracts. For that purpose, defatted seeds were sequentially extracted with ethyl acetate, methanol, methanol‐water 70:30 (v/v) and water. Among the extracts tested, methanol extract demonstrated better antioxidant activities (2,2‐diphenyl‐1‐picrylhydrazyl, hydroxyl and superoxide radical) and total phenol content. But the total flavonoid content and the total reducing power was high for methanol‐water. Most active methanol extract was further screened for α‐glucosidase and α‐amylase inhibition. The extract showed strong α‐glucosidase inhibitory potential and mild α‐amylase inhibition. The study indicated that the extraction yield and the antioxidant activities were strongly dependent on the solvent, antioxidant assays and extract concentration. These results demonstrated that sesame meal can be exploited as source of protein and bioactive for the development of functional food.     

Angiotensin‐I‐Converting Enzyme Inhibitory Activities and In Vivo Antihypertensive Effects of Sardine Protein Hydrolysate

In our previous study, an antihypertensive protein hydrolysate was prepared from sardine. This study aimed to investigate the composition of sardine protein hydrolysate (SPH) and it's in vivo antihypertensive effect. SPH was separated sequentially with ultrafiltration and size exclusion chromatography. Fractions with high angiotensin‐I‐converting enzyme (ACE) inhibitory activity were further analyzed with RP‐HPLC and amino acids analysis. Then, SPH was individually oral administrated to spontaneously hypertensive rats (SHR) and normotensive wistar kyoto rats (WKY) for 4 wk. After treatment, the systolic blood pressure (SBP), organ index, oxidative status, serum ACE activity, and serum angiotensin‐II (ANG‐II) of all the rats were determined. According to the separation and analysis results, 3 main fractions with high ACE‐inhibitory activity were obtained with different amino acids composition. The animal experiments results showed that SPH could significantly reduce SBP (P < 0.05 or P < 0.01) within 4 h after a single oral administration. After a chronic oral administration, a steady state of SBP in SHR rats was attained. The heart weight index and left ventricular weight index were significantly reduced (P < 0.05) in SPH‐treated SHR rats. The malonyldialdehyde (MDA) levels in organs and serum, serum ACE activity, and serum ANG‐II concentration in SPH‐treated SHR rats were significantly lowered (P < 0.05 or P < 0.01) as compared to their controls. Meanwhile there was no significant effect (P > 0.05) on those parameters in WKY rats. These results indicate that SPH can decrease blood pressure in SHR rats and not in WKY rats.     

α‐Glucosidase Inhibitory Activities of Fatty Acids Purified from the Internal Organ of Sea Cucumber Stichopus japonicas

α‐Glucosidase inhibitory activities of the various solvent fractions (n‐hexane, CHCl₃, EtOAc, BuOH, and water) of sea cucumber internal organ were investigated. 1,3‐Dipalmitolein (1) and cis‐9‐octadecenoic acid (2) with potent α‐glucosidase inhibitory activity were purified from the n‐hexane fraction of sea cucumber internal organ. IC₅₀ values of compounds 1 and 2 were 4.45 and 14.87 μM against Saccharomyces cerevisiae α‐glucosidase. These compounds mildly inhibited rat‐intestinal α‐glucosidase. In addition, both compounds showed a mixed competitive inhibition against S. cerevisiae α‐glucosidase and were very stable at pH 2 up to 60 min. The K_I values of compounds 1 and 2 were 0.48 and 1.24 μM, respectively. Therefore, the internal organ of sea cucumber might be a potential new source of α‐glucosidase inhibitors suitably used for prevention of obesity and diabetes mellitus.     

Optimization and Scale‐Up Preparation of Egg White Hydrolysate with Angiotensin I Converting Enzyme Inhibitory Activity

Angiotensin I converting enzyme (ACE) plays an important role in regulation of blood pressure as it converts angiotensin I into angiotensin II (a potent vasoconstrictor). Food protein‐derived ACE inhibitory peptides have been considered as a safer alternative to antihypertensive drugs. In our previous study, three ACE inhibitory peptides were characterized from egg white ovotransferrin and their antihypertensive activity has been validated in spontaneously hypertensive rats. However, it is too costly to prepare these peptides from purified egg white ovotransferrin. The aims of the study were to determine the feasibility of preparing these peptides using egg white and then to optimize the conditions of preparing egg white hydrolysate. Taguchi's method was used to design experiments for optimization, which was established as follows: substrate %, pH of thermoase, time of thermoase digestion, ratio of pepsin to substrate, pH of pepsin, temperature of pepsin, and time of pepsin digestion were 7.5%, pH 8, 90 min, 1%, pH 2.5, 55 °C, and 180 min, respectively. The ACE inhibitory activity (IC₅₀ value) and peptide yield obtained under optimal condition were 30 ± 2 μg/mL and 77.5% ± 0.3%, respectively, which were comparable to the predicted values. Hydrolysate prepared at 150 L reactor showed comparable activity but low peptide yield. Results of this study demonstrated the feasibility of using egg white protein as the starting material to prepare a functional ingredient with potent ACE inhibitory activity.     

Screening of β‐Glucosidase and β‐Xylosidase Activities in Four Non‐Saccharomyces Yeast Isolates

The finding of new isolates of non‐Saccharomyces yeasts, showing beneficial enzymes (such as β‐glucosidase and β‐xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non‐Saccharomyces yeasts. Four isolates were selected because of their both high β‐glucosidase and β‐xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB‐medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β‐glucosidase and β‐xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β‐glucosidase and β‐xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3‐folds) when wines were treated with non‐Saccharomyces isolates. In detail, terpineol, 4‐vinyl‐phenol and 2‐methoxy‐4‐vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2‐phenyl ethanol than those inoculated with other yeasts.     

Comparison of Polyphenol Profile and Inhibitory Activities Against Oxidation and α‐Glucosidase in Mulberry (Genus Morus) Cultivars from China

Mulberry (genus Morus) is a significant source of polyphenols, which can promote positive effects on human health. China has various mulberry cultivars, however, many Chinese mulberry cultivars have been only minimally studied. To solve this lack of research, 8 mulberry cultivars (Da10, Tang10, Yueshen74, Yuefenshen, Longsang, Ningxia1hao, Taiwanguosang, and Baiyuwang) from 4 regions of China were assessed to determine their polyphenol profiles using HPLC‐MS/MS and then tested for their antioxidant and anti‐α‐glucosidase activities in vitro. A total of 18 nonanthocyanins and 4 anthocyanins were quantified in mulberry cultivars; among these polyphenols, chlorogenic acid, quercetin 3‐O‐rutinoside, and cyanidin 3‐O‐glucoside were confirmed as the major phenolic acid, flavonol derivative, and anthocyanin, respectively. Two types of stilbene compounds, piceid, and piceatannol, were detected for the 1st time in all mulberry cultivars. Moreover, the methanolic extracts of different mulberry cultivars showed disparate antioxidant and α‐glucosidase inhibitory activities, and this discrepancy was mainly attributed to varying the anthocyanin content. Based on our results, Taiwanguosang is proposed to be a good candidate suitable for further process due to its high level of anthocyanins.     

Purification,Identification, and In Vivo Activity of Angiotensin I‐Converting Enzyme Inhibitory Peptide,from Ribbonfish (Trichiurus haumela) Backbone

Ribbonfish (Trichiurus haumela) backbone is normally discarded as an industrial waste from fish processing. A method of developing angiotensin I‐converting enzyme inhibitory (ACEI) peptides from ribbonfish backbone was previously optimized. The purposes of the study were to characterize the active peptides in the hydrolysate and to evaluate its in vivo activity. Ribbonfish backbone protein hydrolysate prepared by acid protease was fractionated into 4 fractions (I, MW < 1 kDa; II, MW = 1 to 5 kDa; III, MW = 5 to 10 kDa; and IV, MW > 10 kDa) through ultrafiltration membranes. Fraction I, showing the highest ACEI activity, was further purified using consecutive chromatographic techniques including gel filtration and reversed phase high‐performance liquid chromatography. The purified ACE inhibitory peptide was determined to have a molecular weight of 317.25 Da, with a sequence of Leu‐Trp and an IC₅₀ value of 5.6 μM. Systolic blood pressure of spontaneously hypertensive rats was significantly decreased from 181 ± 2.0 to 161.3 ± 2.3 mm Hg after 4 h of oral administration of Leu‐Trp at a dose of 10 mg/kg of body weight. These results indicated that ribbonfish backbone protein could be used for development of antihypertensive agent.     

Detection of β‐Glucosidase and Esterase Activities in Wild Yeast in a Distillery Environment

The study of β‐glucosidase and esterase in wild yeast, the enzymatic activities of which contribute to the distinctive flavours of grape‐derived alcoholic beverages, was the aim of this work. The study focused on wild yeast isolated from grape pomace and on identifying strains with interesting characteristics by examining their electrophoretic profiles. Zymograms revealed a high level of polymorphism. Some of these wild yeasts may be of interest for improving the quality of the distillate. This study also highlights the necessity of associating enzymatic properties to various environmental conditions, since these play an important role in the expression of wild yeast performance.