A novel phenolic formulation for treating hepatic and peripheral insulin resistance by regulating GLUT4-mediated glucose uptake.

Chronic insulin resistance suppresses muscle and liver response to insulin, which is partially due to impaired vesicle trafficking. We report here that a formula consisting of resveratrol, ferulic acid and epigallocatechin-3-O-gallate is more effective in ameliorating muscle and hepatic insulin resistance than the anti-diabetic drugs, metformin and AICAR. The formula enhanced glucose transporter-4 (GLUT4) translocation to the plasma membrane in the insulin-resistant muscle cells by regulating both insulin-independent (calcium and AMPK) and insulin-dependent (PI3K) signaling molecules. Particularly, it regulated the subcellular location of GLUT4 through endosomes to increase glucose uptake under insulin-resistant condition. Meanwhile, this phytochemicals combination increased glycogen synthesis and decreased glucose production in the insulin-resistant liver cells. On the other hand, this formula also showed anti-diabetic potential by the reduction of lipid content in the myotubes, hepatocytes, and adipocytes. This study demonstrated that the three phenolic compounds in the formula could work in distinct mechanisms and enhance both insulin-dependent and independent vesicles trafficking and glucose transport mechanisms to improve carbohydrate and lipid metabolism.

Evaluation of Phenolic Phytochemical Enriched Commercial Plant Extracts on the In Vitro Inhibition of α-Glucosidase.

Green tea (GT), cranberry (CR), and tart cherry extracts were evaluated for their ability to inhibit yeast α-glucosidase, relevant to glucose uptake. The total phenolic content (TPC), antioxidant activity, and in vitro inhibitory activity of yeast α-glucosidase were examined for the extracts in the present study. GT had higher TPC and antioxidant activity, but CR demonstrated a greater α-glucosidase inhibitory activity, on phenolic basis. CR was fractionated using LH-20 column chromatography into two fractions: 30% methanol (CME) and 70% acetone (CAE). TPC, antioxidant activity, and yeast α-glucosidase inhibitory activity were determined for the fractions. CAE had a greater TPC and antioxidant activity than CME, but the two fractions had a synergistic effect when inhibiting yeast α-glucosidase. Our findings suggest that CR has the greatest potential to possibly manage post-prandial blood glucose levels via the inhibition of α-glucosidase, and that the effect is through synergistic activity of the extract's phenolic compounds.

Rapid Screening of Natural Plant Extracts with Calcium Diacetate for Differential Effects Against Foodborne Pathogens and a Probiotic Bacterium.

This study focused on advancing a rapid turbidimetric bioassay to screen antimicrobials using specific cocktails of targeted foodborne bacterial pathogens. Specifically, to show the relevance of this rapid screening tool, the antimicrobial potential of generally recognized as safe calcium diacetate (DAX) and blends with cranberry (NC) and oregano (OX) natural extracts was evaluated. Furthermore, the same extracts were evaluated against beneficial lactic acid bacteria. The targeted foodborne pathogens evaluated were Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus using optimized initial cocktails (∼108 colony-forming unit/mL) containing strains isolated from human food outbreaks. Of all extracts evaluated, 0.51% (w/v) DAX in ethanol was the most effective against all four pathogens. However, DAX when reduced to 0.26% and with added blends from ethanol extractions consisting of DAX:OX (3:1), slightly outperformed or was equal to same levels of DAX alone. Subculture of wells in which no growth occurred after 1 week indicated that all water and ethanol extracts were bacteriostatic against the pathogens tested. All the targeted antimicrobials had no effect on the probiotic organism Lactobacillus plantarum. The use of such rapid screening methods combined with the use of multistrain cocktails of targeted foodborne pathogens from outbreaks will allow rapid large-scale screening of antimicrobials and enable further detailed studies in targeted model food systems.

Stimulation of Phenolics, Antioxidant and α-Glucosidase Inhibitory Activities During Barley (Hordeum vulgare L.) Seed Germination.

The rationale of this study was to enhance the nutritional quality of dry barley seeds. In this study we are evaluating the effect of germination on barley seeds relevant to total phenolic contents, antioxidant activity (in terms of DPPH free-radical scavenging) and the in vitro α-glucosidase inhibitory activities. Barley seeds were germinated for 18.5, 24, 30, 48, and 67 h and then extracted in water. The total phenolic contents, antioxidant activities and α-glucosidase inhibitory activities changed with germination time. More specifically, within the first 48 h of germination the total phenolic content increased from 1.1 mg/g fresh weight (0 h) to 3.4 mg/g fresh weight (48 h) and then slightly reduced by 67 h. Similarly, α-glucosidase inhibitory activity was significantly increased from an IC50 128.82 mg/mL (0 h) to an IC50 18.88 mg/mL (48 h) and then slightly reduced by 67 h. Significant maltase inhibitory activity was observed only with 48 h-germinated extract. Antioxidant activities increased continuously from an IC50 15.72 mg/mL at 0 h to and IC50 5.72 mg/mL after 48 h of germination. Based on our observations, barley seed germination was over after 48 h. During the progress of germination phenolic compounds are becoming available and are more easily extracted. After 48 h, lignification is initiated resulting to the decreased total phenolic content and observed antioxidant and carbohydrate hydrolyzing enzyme inhibition activities. The above results indicate the positive effect of germination in barley seeds for enhanced antioxidant and α-glucosidase inhibitory activities.