Molecular Weight Affected Antioxidant,Hypoglycemic and Hypotensive Activities of Cold Water Extract from Pleurotus citrinopileatus

Cold water extract of P. citrinopileatus (CWEPC) was fractioned into 4 fractions, PC‐I (<1 kDa), PC‐II (1‐3.5 kDa), PC‐III (3.5‐10 kDa), and PC‐IV (>10 kDa), by ultrafiltration. The antioxidant activities, the inhibition of pancreatic α‐amylase, intestinal α‐glucosidase, and hypertension‐linked angiotensin converting enzyme (ACE), as well as the contents of polysaccharides, protein, and phenolic compounds of 4 fractions were determined. The results showed that lower MW fractions exerted a higher antioxidant activity, which was correlated to phenolic contents. The high molecular fraction (PC‐IV) exhibited significantly higher inhibitory activity on α‐amylase, α‐glucosidase, and ACE compared to CWEPC and the other 3 lower MW fractions (<10 kDa), which was more related to protein contents. The inhibition capability of CWEPC and PC‐IV on α‐amylase activity was 1/13.4 to 1/2.7 relative to that of acarbose, respectively. Kinetic data revealed that PC‐IV fraction followed a noncompetitive inhibition pattern on α‐glucosidase activity. The study demonstrated that various MW fractions and types of components contribute to different biological functions of P. citrinopileatus and it is protein constituents but not peptides responsible for the hypoglycemic potential of CWEPC.     

Anti‐acetylcholinesterase,antidiabetic, anti‐inflammatory,antityrosinase and antixanthine oxidase activities of Moroccan propolis

Biological properties of Moroccan propolis have been scarcely studied. In the present work, the total phenols and flavonoids from 21 samples of propolis collected in different places of Morocco or 3 supplied in the market were determined, as well as the in vitro capacity for inhibiting the activities of acetylcholinesterase, α‐glucosidase, α‐amylase, lipoxygenase, tyrosinase, xanthine oxidase and hyaluronidase. The results showed that samples 1 (region Fez‐Boulemane, Sefrou city) (IC₅₀ = 0.065, 0.006, 0.020, 0.050, 0.014 mg mL^?1) and 23 (marketed) (IC₅₀ = 0.018, 0.002, 0.046, 0.037, 0.008 mg mL^?1) had the best in vitro capacity for inhibiting the α‐amylase, α‐glucosidase, lipoxygenase, tyrosinase and xanthine oxidase activities, respectively. A negative correlation between IC₅₀ values and concentration of phenols, flavones and flavanones was found. These activities corresponded to the generally higher amounts of phenols and flavonoids. In the same region, propolis samples have dissimilar phenol content and enzyme inhibitory activities.     

In vitro inhibitory effects of cranberry bean (Phaseolus vulgaris L.) extracts on aldose reductase, α‐glucosidase and α‐amylase

The in vitro inhibitory activities of different seed extracts prepared from cranberry bean mutant SA‐05 and its wild‐type variety Hwachia against aldose reductase, α‐glucosidase and α‐amylase were examined. The results indicated that the polyphenolics‐rich extracts obtained using 800 g kg^?1 methanol and 500 g kg^?1 ethanol demonstrated inhibitory activities against aldose reductase (IC₅₀ of 0.36–0.46 mg mL^?1) and α‐glucosidase (IC₅₀ of 1.32–1.94 mg mL^?1). The 500 g kg^?1 ethanol extracts also showed α‐amylase inhibitory activities (IC₅₀ of 70.11–80.22 μg mL^?1). Subsequent extracts, prepared further with NaCl and H₂O from precipitates of 800 g kg^?1 methanol or 500 g kg^?1 ethanol extracts, exhibited potent α‐amylase inhibitory activities (IC₅₀ of 17.68–38.68 μg mL^?1). A combination of 500 g kg^?1 ethanol extraction plus a subsequent H₂O extraction produced highest polyphenolics and α‐amylase inhibitors. The SA‐05 α‐amylase inhibitor extracts showed greater inhibitory activities than that of Hwachia. Thus, cranberry bean mutant SA‐05 is an advantageous choice for producing anti‐hyperglycaemic compounds.     

Inhibitory activities of kaempferol,galangin, carnosic acid and polydatin against glycation and α‐amylase and α‐glucosidase enzymes

The activities of four natural phenolics, kaempferol, galangin, carnosic acid and polydatin in scavenging free radicals, inhibiting advanced glycation end‐product (AGE) formation, α‐amylase and α‐glucosidase and trapping methylglyoxal (MGO), were evaluated in this study. Carnosic acid and galangin had the highest activity in scavenging free radicals. Kaempferol and galangin had the greatest activity in preventing bovine serum albumin (BSA) against glycation and reducing glycated proteins. Polydatin had the greatest performance in trapping MGO to reduce glycation reaction. However, there was no significant difference for kaempferol, galangin and carnosic acid in inhibiting AGE formation by BSA‐MGO reaction. Kaempferol, galangin and carnosic acid were the competitive inhibitors for α‐amylase, while kaempferol and carnosic acid were noncompetitive inhibitors for α‐glucosidase. However, polydatin showed as a mixed noncompetitive inhibitor for both α‐amylase and α‐glucosidase. The results indicated that the four natural phenolics have potential in inhibiting AGE production and the digestive enzymatic activity with different mechanisms.     

α‐Glucosidase and α‐amylase inhibitory activities of phloroglucinal derivatives from edible marine brown alga,Ecklonia cava

BACKGROUND: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by defects in insulin secretion and action, which can lead to damaged blood vessels and nerves. With respect to effective therapeutic approaches to treatment of DM, much effort has being made to investigate potential inhibitors against α‐glucosidase and α‐amylase from natural products. The edible marine brown alga Ecklonia cava has been reported to possess various interesting bioactivities, which are studied here. RESULTS: In this study, five phloroglucinal derivatives were isolated from Ecklonia cava: fucodiphloroethol G ( 1 ), dieckol ( 2 ), 6,6′‐bieckol ( 3 ), 7‐phloroeckol ( 4 ) and phlorofucofuroeckol A ( 5 ); compounds 1, 3 and 4 were obtained from this genus for the first time and with higher yield. The structural elucidation of these derivatives was completely assigned by comprehensive analysis of nuclear magnetic spectral data. The anti‐diabetic activities of these derivatives were also assessed using an enzymatic inhibitory assay against rat intestinal α‐glucosidase and porcine pancreatic α‐amylase. Most of these phlorotannins showed significant inhibitory activities in a dose‐dependent manner, responding to both enzymes, especially compound 2 , with the lowest IC₅₀ values at 10.8 µmol L^?1 (α‐glucosidase) and 124.9 µmol L^?1 (α‐amylase), respectively. Further study of compound 2 revealed a non‐competitive inhibitory activity against α‐glucosidase using Lineweaver‐Burk plots. CONCLUSION: These results suggested that Ecklonia cava can be used for nutritious, nutraceutical and functional foods in diabetes as well as for related symptoms. Copyright © 2009 Society of Chemical Industry     

Screening grape seeds recovered from winemaking by‐products as sources of reducing agents and mammalian α‐glucosidase and α‐amylase inhibitors

Grape seeds collected from vinification of various grape varieties were extracted by supercritical CO₂ for oil recovery. The defatted residues thus obtained were considered as a re‐utilisable co‐product and assessed for phenolic content, reducing capacity and inhibitory activities against mammalian α‐amylase and α‐glucosidase enzymes. Supercritical CO₂ treatment led to higher recovery of anthocyanins. Reducing capacity of phenolic extracts reached up to ~2200 mmolFe(II) kg^?1, much higher than that of various natural phenolic sources. The anthocyanin‐rich extracts showed the highest inhibitory effectiveness towards α‐glucosidase (I₅₀ value equal to ~40 μg gallic acid equivalents (GAE)/mL ~ half than acarbose). Inhibitory effectiveness towards α‐amylase activity was similar among grape varieties, with I₅₀ values comparable to that of acarbose and correlated with proanthocyanidin contents. These results could pave the way for an efficient processing of grapes, including cascade processes, namely: winemaking, oil extraction from recovered grape seeds and phenolic extraction from defatted grape seeds as potential cost‐effective nutraceuticals.     

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.     

Enhancement of the antioxidant and starch hydrolase inhibitory activities of king coconut water (Cocos nucifera var. aurantiaca) by fermentation with kombucha ‘tea fungus’

Enhancement of antioxidant and starch hydrolase inhibitory properties of king coconut water when subjected to fermentation with the ‘tea fungus’ was evaluated. pH, colour, viscosity, ethanol content, antioxidant activity, total phenolic content, ferulic and p‐coumaric acid contents and starch hydrolase inhibitory activities were analysed for 7 days in fermented and unfermented king coconut water samples. The fermented sample had a statistically significant decrease (P < 0.05) in pH. Colour values indicated the fermented beverage to increase in ‘yellowness’ over time. A statistically significant increase in the total phenolic content and the antioxidant activity (P < 0.05) was observed from day 1 onwards in the fermented sample. The starch hydrolase inhibitory activities in the fermented beverage had statistically significantly increased (P < 0.05) by day 7. Overall, the study highlights an enhancement of the antioxidant and starch hydrolase inhibitory properties of king coconut water as a result of the kombucha‐based fermentation.     

Interaction of aqueous extracts of two varieties of Yam tubers (Dioscorea spp) on some key enzymes linked to type 2 Diabetes in vitro

This study sought to assess the effect of processing of yam flour [from white yam (Dioscorea rotundata) and water yam (Dioscorea alata)] to paste, on the antioxidant properties and inhibition of key enzymes linked to type‐2 diabetes (α‐amylase and α‐glucosidase). The phenolic content (phenol and flavonoid), antioxidant properties, α‐amylase and α‐glucosidase inhibitory properties of the aqueous extracts of the yam products were determined. Processing into paste caused significant (P < 0.05) percentage decrease in their total phenol and flavonoid content of the yam varieties. However, significant increase (P < 0.05) in the antioxidant properties of the yam varieties was observed after processing. Furthermore, the yam extracts inhibited α‐amylase and α‐glucosidase activities in vitro in a dose‐dependent parttern (1–4 mg mL^?1), however, the pasting process caused significant (P < 0.05) decrease in the α‐amylase inhibitory and α‐glucosidase inhibitory activities. Therefore, processing the yam varieties into paste (browned) could potentially increase their antioxidant capacity as well as decreasing their α‐amylase and α‐glucosidase inhibitory properties.     

Improvement in antioxidant activity,angiotensin‐converting enzyme inhibitory activity and in vitro cellular properties of fermented pepino milk by Lactobacillus strains containing the glutamate decarboxylase gene

BACKGROUND: The purpose of this study was to evaluate the functional potential of fermented pepino extract (PE) milk by Lactobacillus strains containing the glutamate decarboxylase (GAD) gene. Three Lactobacillus strains were selected, including L. brevis BCRC 12310, L. casei BCRC 14082 and L. salivarius subsp. salivarius BCRC 14759. The contents of free amino acids, total phenolics content, total carotenoids and the associated functional and antioxidant abilities were analyzed, including angiotensin‐converting enzyme (ACE) inhibition activity, 1,1‐diphenyl‐2‐picylhydrazyl (DPPH) radical‐scavenging ability and oxygen radical absorbance capacity (ORAC). Cell proliferation of fermented PE milk was also evaluated by MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay. RESULTS: Compared to the unfermented PE, fermented PE milk from Lactobacillus strains with the GAD gene showed higher levels of total phenolics, γ‐aminobutyric acid, ACE inhibitory activity, DPPH, and ORAC. The viability of human promyelocytic leukemia cells (HL‐60) determined by the MTT method decreased significantly when the cells were incubated with the PE and the fermented PE milk extracts. CONCLUSION: The consumption of fermented PE milk from Lactobacillus strains with the GAD gene is expected to benefit health. Further application as a health food is worthy of investigation. © 2012 Society of Chemical Industry     

Inhibitory potential of phenylpropanoid glycosides from Ligustrum purpurascens Kudingcha against α‐glucosidase and α‐amylase in vitro

The leaves of Ligustrum purpurascens are used in a Chinese traditional tea called small‐leaved kudingcha, which is rich in phenylpropanoid glycosides (PPGs) and has many beneficial properties. Two critical exoacting glycoside hydrolase enzymes (glucosidases) involved in carbohydrate digestion are α‐glucosidase and α‐amylase. We investigated the properties of PPGs from L. purpurascens for inhibiting α‐amylase and α‐glucosidase activity in vitro and found IC₅₀ values of 1.02 and 0.73 mg mL^?1, respectively. The patterns of inhibiting both α‐amylase and α‐glucosidase were mixed‐inhibition type. Multispectroscopy and molecular docking studies indicated that the interaction between PPGs and α‐amylase and α‐glucosidase altered the conformation of enzymes, with binding at the site close to the active site of enzymes resulting in changed enzyme activity. Our studies may help in the further health use of small‐leaved kudingcha.     

Enzyme activities,dietary fibre components and rheological properties of wholemeal flours from rye cultivars grown in Finland

Total and soluble dietary fibre, total and soluble pentosan and β‐glucan contents, activities of α‐amylase (EC 3.2.1.1) and endo‐β‐xylanase (EC 3.2.1.8) and viscous properties of aqueous suspensions of wholemeal flours during heating were determined in nine winter rye cultivars (Secale cereale L) grown in Finland in 1998–2001. There was marked annual and varietal differences in grain quality. In the rainy summer 1998 the yield was low, grains were small and dietary fibre content of the grains was high. Xylanase activity of the grains was high, which corresponded to the high content of soluble pentosans. In the dry summer of 1999, the pentosan content of the grains was low and β‐glucan content high. The effect of weather conditions and cultivar were also apparent in the differences in falling numbers, amylogram and swelling curve results. The two hybrid rye cultivars Esprit and Picasso had consistently highest falling numbers and amylogram peak viscosities. The activities of α‐amylase and xylanase had a moderate positive correlation with total pentosan content and the content of soluble pentosan. Xylanase activity had better correlation with the viscous properties of flour–water suspensions than α‐amylase. Surprisingly, α‐amylase activity had only a moderate negative correlation with falling number. Copyright © 2005 Society of Chemical Industry