PCL/Yam Polysaccharide nanofibrous membranes loaded with self-assembled HP-β-CD/ECG inclusion complexes for food packaging

In this study, Polycaprolactone (PCL)/Yam Polysaccharide (YP) fiber membranes loaded the ultrasound-mediated assembly of 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD)/Epicatechin gallate (ECG) inclusion complexes were prepared by electrospinning technology for food packaging. Morphology, infrared spectroscopy and X-ray diffraction results showed that the inclusion complexes were successfully assembled. With the addition of inclusion complexes, the average diameter of the fibers increased from 2480.96 to 10179.12 nm, the crystallinity decreased, the thermal stability improved, the hydrophilicity enhanced, and the water vapor permeability enhanced. Meanwhile, thermogravimetry and differential scanning calorimetry results showed that the inclusion complexes formed hydrogen bonds between the fibers, which improved the thermal stability, but the mechanical behavior suffered a certain loss. In addition, the fiber membrane could continuously release ECG within 240 h, which showed excellent antibacterial effects both in vitro and in vivo. These results indicated that the fiber film developed based on electrospinning had a broad application prospect in food packaging.

Preparation, characterization and application of antioxidant packaging films based on chitosan-epicatechin gallate conjugates with different substitution degrees

In this study, chitosan (CS) was conjugated with epicatechin gallate (ECG) to prepare CS-ECG conjugates with different substitution degrees (5.18 %, 6.36 % and 7.74 %). Then, antioxidant packaging films were fabricated by blending CS and CS-ECG conjugates. The impact of CS-ECG conjugates' substitution degree on the functionality of CS/CS-ECG films was determined. CS-ECG conjugates showed UV absorption at 275 nm, proton signal at 6.85 ppm and infrared absorption at 1533 cm-1, assigning to the conjugated ECG. As compared with CS, CS-ECG conjugates exhibited less crystalline state but higher antioxidant activity. The structural characterization of CS/CS-ECG films showed CS and CS-ECG conjugates formed hydrogen bonds. CS/CS-ECG films displayed 26.35 %-29.23 % water solubility, 85.61°-86.96° water contact angle, 3.11-3.41 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 0.29-0.34 cm3 mm m-2 day-1 atm-1 oxygen permeability, 31.54-36.20 MPa tensile strength, 50.12 %-56.40 % elongation at break, as well as potent antioxidant activity and oil oxidation inhibitory ability. Notably, the film containing CS-ECG conjugate with 7.74 % substitution degree had the strongest barrier ability, mechanical property, antioxidant activity and oil oxidation inhibitory ability. Results suggested the substitution degree of CS-ECG conjugates was positively correlated with the barrier, mechanical and antioxidant properties of CS/CS-ECG films.

Anti-adhesive activity of some secondary metabolites against Staphylococcus aureus on 3D printing medical materials

Recent improvements in 3D printing technology have increased the usage of 3D printed materials in several areas. An exciting and emerging area of applying these next-generation manufacturing strategies is the development of devices for biomedical applications. The main aim of this work was to investigate the effect of tannic acid, gallic acid, and epicatechin gallate on the physicochemical characteristics of acrylonitrile butadiene-styrene (ABS) and Nylon 3D printing materials using the contact angle method. The adhesion of Staphylococcus aureus on untreated and treated materials was evaluated by scanning electron microscopy (SEM) analysis and the images were treated by MATLAB software. The results of the contact angle measurements showed a significant change in the physicochemical properties of both surfaces, indicated an increase in the electron donor character of 3D printing materials following treatment. Thus, the ABS surfaces treated with tannic acid, gallic acid, and epicatechin gallate have become more electron donating. Furthermore, our results proved the ability of S. aureus to adhere on all materials with a percentage of 77.86% for ABS and 91.62% for nylon. The SEM has shown that all actives molecules were sufficient to obtain better inhibition of bacterial adhesion, which tannic acid has shown a total inhibition of S. aureus on ABS. From these results, our treatment presents a high potential for utilization as an active coating to prevent bacterial attachment and the eventual biofilm development in medical field.

Epicatechin gallate promotes vascularization in co-culture of human osteoblasts and outgrowth endothelial cells

Prevascularization is crucial for the survival of tissue-engineered bone and further bone repair/regeneration. Since epicatechin gallate (ECG), the most abundant flavanol in green tea, shows potential beneficial effects on endothelial cells and bone cells, we decided to investigate whether it promotes vascularization/angiogenesis and osteogenesis using a co-culture system containing human primary osteoblasts (POBs) and outgrowth endothelial cells (OECs). We found that treatment with ECG (1) significantly enhanced microvessel formation in co-culture of POB and OECs, (2) improved cell viability/proliferation and the angiogenic/osteogenic capacities of OEC/POBs, (3) significantly increased the levels of E-selectin, IL-6, TNF-α, IFN-γ, VEGF, and PDGF-BB in co-cultures of POB and OEC, and (4) upregulated HIF-1α, HIF-2α, NF-κB, iNOS, GLUT1, VEGF, and Ang1/2 but downregulated PHD1 in monocultures of OEC or POB. Our findings demonstrate that ECG promotes angiogenesis and osteogenesis (probably via HIF signaling) in co-cultures of OECs and POBs. ECG thus has potential applications in the promotion of angiogenesis/vascularization in many tissue constructs including those of bone.

Solid fuel derived PM2.5 induced oxidative stress and according cytotoxicity in A549 cells: The evidence and potential neutralization by green tea

PM_2.5 (particulate matter with aerodynamic diameter ≤ 2.5 μm) is a well-known cytotoxic pollutant that capable to induce severe intracellular oxidative stress while the underlying mechanisms remain unclear. Herein, 4 types of PM_2.5 derived from solid fuel burning were selected as stimuli in A549 cells exposure model to evaluate their effects on oxidative stress and inflammatory responses. Although resulting in different responses in cell viability, all PM_2.5 exhibited over 50 % higher oxidative stress than control group, expression as intracellular reactive oxygen species, malondialdehyde and superoxide dismutase levels. The Pearson's correlation results indicated that cations (e.g., Ca²⁺), heavy metals (e.g., Cr and Pb), nPAHs (nitro-polycyclic aromatic hydrocarbons, e.g., 6-nitrochrysene) and oPAHs (oxygenated PAHs, e.g., 9-fluorenone) were the main functioning toxics (r > 0.6). A key finding was the dual-directional regulation function of ECG (epicatechin gallate), that is, it could either increase the low A549 cell viabilities in coal combustion PM_2.5 group or reduce them in charcoal PM_2.5 group (P < 0.05). The dual-directional effects were likely because ECG can activate Nrf2 oxidation signaling pathway then inhibit the inflammatory signaling pathway NF-κB accordingly. Therefore, evidences indicated cytotoxicity of solid fuel derived PM_2.5 were mainly caused by oxidative stress, which was proved to be reversed by green tea, providing a potential therapy method to PM_2.5 and other hazards.

WITHDRAWN: Epicatechin gallate-loaded calcium alginate sponges promote diabetic wound healing through protecting against oxidative stress and modulation of immune response via PI3K/AKT/NFκB signaling pathway

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Pre-concentration of active principles from different varieties of Camellia sinensis extracts by solid sorbents

In this article we studied the phytochemical composition of leaves extracts of different varieties of Camellia sinensis(L.) Kuntze after treatment with 16 selected solid sorbents (namely hydrotalcites, magnesium oxide and hydroxide, zirconium phosphates, and phyllosilicates). The pre-concentration and selective adsorption of the main active principles of this food and medicinal plant [e.g. gallic acid, (-)-epicatechin, (-)-epicatechin gallate, and caffeine] were investigated. The quantities of phytochemicals adsorbed by solids were measured by HPLC analysis, coupled to photodiode array detection and calculated as the difference between the quantities in the parent untreated extracts and those recorded in the filtrates. Caffeine was selectively adsorbed by bentonite to a large extent, while for the remaining phytochemicals different patterns were recorded depending on the type of leaves extract. A comparison with pure chemicals revealed a strong effect of the phytocomplex composition on the adsorption yields. The methodology outlined herein may be useful to obtain tea extracts enriched in selective active principles also for industrial scopes.

Green tea flavanols protect human γB-crystallin from oxidative photodamage

Age related cataract is a major cause of visual loss worldwide that is a result of opacification of the eye lens proteins. One of the major reasons behind this deterioration is UV induced oxidative damage. The study reported here is focused on an investigation of the oxidative stress induced damage to γB-crystallin under UV exposure. Human γB-crystallin has been expressed and purified from E. coli. We have found that epicatechin gallate (ECG) has a higher affinity towards the protein compared to epigallocatechin (EGC). The in vitro study of UV irradiation under oxidative damage to the protein in the presence of increasing concentrations of GTPs is indicative of their effective role as potent inhibitors of oxidative damage. Docking analyses show that the GTPs bind to the cleft between the domains of human γB-crystallin that may be associated with the protection of the protein from oxidative damage.

Recent advances in understanding the anti-diabetic actions of dietary flavonoids

Flavonoids are polyphenolic compounds that are abundant in fruits and vegetables, and increasing evidence demonstrates a positive relationship between consumption of flavonoid-rich foods and disease prevention. Epidemiological, in vitro and animal studies support the beneficial effects of dietary flavonoids on glucose and lipid homeostasis. It is encouraging that the beneficial effects of some flavonoids are at physiological concentrations and comparable to clinically-used anti-diabetic drugs; however, clinical research in this field and studies on the anti-diabetic effects of flavonoid metabolites are limited. Flavonoids act on various molecular targets and regulate different signaling pathways in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibers. Flavonoids may exert beneficial effects in diabetes by (i) enhancing insulin secretion and reducing apoptosis and promoting proliferation of pancreatic β-cells; (ii) improving hyperglycemia through regulation of glucose metabolism in hepatocytes; (iii) reducing insulin resistance, inflammation and oxidative stress in muscle and fat and (iv) increasing glucose uptake in skeletal muscle and white adipose tissue. This review highlights recent findings on the anti-diabetic effects of dietary flavonoids, including flavan-3-ols, flavanones, flavonols, anthocyanidins, flavones and isoflavones, with particular emphasis on the studies that investigated the cellular and molecular mechanisms involved in the beneficial effects of the compounds.