Karima Dhaouadi

Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis.

Comparative Analysis of Tunisian Wild Crataegus azarolus (Yellow Azarole) and Crataegus monogyna (Red Azarole) Leaf, Fruit, and Traditionally Derived Syrup: Phenolic Profiles and Antioxidant and Antimicrobial Activities of the Aqueous-Acetone Extracts

Quantitative and qualitative analyses of the yellow and red azarole phenolic extracts prepared from leaf, fruit peel/pulp, and syrup were comparatively investigated. The yellow azarole was found significantly richer in polyphenols than the red-fruit species. Hyperoside was the main phenolic in both yellow and red azarole leaves and only in yellow fruits, whereas procyanidin B2 was the major compound in red fruits. Yellow azarole leaf and fruit peel extracts exhibited the strongest antioxidant activities using DPPH (≈168 and 79 μmol TEAC/g fw, respectively) and FRAP (≈378 and 161 μmol Fe(2+)/g fw, respectively) assays. The highest antibacterial activities were recorded for the yellow azarole leaf and fruit peel extracts, especially against Staphylococcus aureus and Streptococcus faecalis . The low phenolic content of the syrups contrasted with their significant antioxidant and antimicrobial potentials, which were correlated to their hydroxymethylfurfural (HMF) (furan derivative amounts) content.

Antioxidant and Antimicrobial Activities of Tunisian Azarole (Crataegus Azarolus L.) Leaves and Fruit Pulp/Peel Polyphenolic Extracts

The polyphenolic extracts prepared from Tunisian azarole (Crataegus azarolus, Rosaceae family) leaves, fruit peel, and pulp parts were investigated. The evaluation of the free 2,2-diphenyl-2-picrylhydrazyl radical-scavenging activity in comparison to that of Trolox, a synthetic antioxidant, showed that the stronger properties were obtained from leaf material followed by fruit peel (2.026 and 1.607 mmol Trolox equivalent antioxidant capacity/g of fresh weight, respectively), whereas fruit pulp extract exhibited weak antioxidant potential (0.883 mmol Trolox equivalent antioxidant capacity/g of fresh weight). Using reverse phase-high phase liquid chromatography-diode array detector and ESI-MS, the phenolic compounds of the extracts were qualitatively and quantitatively determined. The total phenolic content of leaves and fruit peel and pulp were found to be about 152.38, 142.46, and 26.31 mg/100 g of fresh weight, respectively. Isoquercitrin was the main phenolic in the leaves (44.9%), whereas hyperosid (72.01%) and epicatechin (68.41%) were the most abundant compounds in the fruit peel and pulp, respectively. The assessment of the antimicrobial activity of the extracts against a range of Gram positive and Gram negative bacteria revealed that Tunisian azarole leaves and fruit peel extracts exhibited strong potential for inhibiting bacterial growth, especially Staphylococcus aureus and Streptococcus faecalis. minimum inhibitory concentrations and minimum bactericidal concentrations were found in the range of 59.35–118.71 and 42.32–63.49 μg/ml of fruit peel and leaves extracts, respectively.

Short Cooking Time Increases,but Sucrose or SweetenerCounteracts the RadicalScavenging Activities of TeaDecoction as Compared to TeaInfusion

Short Cooking Time Increases, but Sucrose or Sweetener Counteracts the Radical Scavenging Activities of Tea Decoction as Compared to Tea Infusion In contrast to tea infusion (TI), green and black tea decoctions (GTD, BTD) are prepared by cooking tealeaves in boiling water for a relatively long period of time and regularly consumed with sugar. Here, we contrasted the effect of cooking times and sucrose or sweetener “sucralose” on the total phenolic compounds (TPC) content and the potential radical scavenging activities (RSA) of GTD, BTD as compared to the usual TI or dry tealeaves extract. Results showed that GTD and BTD prepared for 15-min exhibited the highest TPC and RSA powerful than TI or GTD, BTD prepared for 30-min or 60-min. Conversely, the addition of sucrose or sucralose had reduced TPC concentration and significantly counteracted the RSA potential of tea extracts. Therefore, 15-min GTD or BTD without sugar showed to be more suitable to preserve the beneficial antioxidant properties of tea after cooking process.