Oxidative stress plays a key role in the pathogenesis of different serious chronic diseases such as cancer, diabetes, cardiovascular and neurodegenerative disorders, etc. Recent research has been focused on the beneficial role of dietary antioxidants against oxidative stress both under in vitro and in vivo conditions. Theobroma cacao L. (cacao tree) is an evergreen tree which is native to South America. It is a plant of great economic importance and its seeds are commonly used to produce cocoa powder and chocolate. In addition to its uses in food industry, cocoa is a rich source of polyphenolic antioxidants. There is a plethora of in vitro and in vivo studies that report cocoa antioxidant capacity. The protective activity of cocoa seems to be due to its phytochemical constituents, especially catechins. However, bioavailability of cocoa polyphenolic constituents following oral administration is very low (nanomolar concentrations). In the present paper, we critically reviewed the available literature on the antioxidant and free radical scavenging activities of cocoa and its polyphenolic constituents. In addition to these, we provide brief information about cultivation, phytochemistry, bioavailability and clinical impacts of cocoa.

Cadmium ion is toxic to organisms and shows persistence because of its nondegradability. Photoreduction of the cadmium ion (Cd­(II)) was studied using a bentonite-supported Zn oxide (ZnO/BT) photocatalyst in an aqueous medium under ultraviolet light. The prepared ZnO/BT photocatalyst was characterized by diffuse reflectance spectroscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, and Brunauer–Emmett–Teller/Barrett–Joyner–Halenda analysis. The effects of main parameters including pH, contact time, initial concentration of cadmium­(II) ion, light intensity, temperature, and the photocatalyst dosage were investigated for obtaining appreciate reduction/removal efficiency. The maximum reduction/removal efficiency of 74.8% was obtained at optimized values which were found to be at pH 5, 6 h contact time, 6 ppm Cd­(II) ion, 200 W UV light, 45 °C temperature, and 4 g/L of ZnO/BT. Reduction/removal of Cd­(II) was significantly affected by light intensity so that the increment in UV intensity from 0 to 200 increased the reduction/removal efficiency from 61.2 to 76.8%. This study reports an inexpensive and environmentally friendly photocatalyst for Cd2+ reduction in real samples and prospective photoelectric materials.

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An electronic nanoswitch is described based on the conformational change of the DNA sequence in the presence of stabilizing ligands. The new electrochemical biosensor was prepared by modifying a screen-printed graphite electrode (SPE) with functionalized SiO2 nanoparticles [(SiO2-N-propylpiperazine-N-(2-mercaptopropane-1-one) (SiO2@NPPNSH)] and Au nanoparticles (AuNPs). These nanoparticles are able to immobilize thiolated G-quadruplex DNA structures (SH-G4DNA). The SH groups on the SiO2@NPPNSH nanoparticles provide a good platform for stabilizing AuNPs on the surface of the electrode. This is due to the fact that AuNPs are able to bind to the organic SH groups on the SiO2@NPPNSH. The SH-G4DNA binds to the modified electrode by a AuNPs-S bond. The structure of SiO2@NPPNSH was characterized by scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA) and infrared (IR) spectroscopy. The morphology of the modified electrode was characterized by SEM. The interaction between G4DNA and the anticancer drug, Tamoxifen (Tam), was studied in Tris-HCl buffer and [Fe(CN)6](3-) using cyclic (CV) and square wave voltammetry (SWV). The G-quadruplex formation and the interaction mechanism were identified by circular dichroism (CD) measurements. The CV current was seen to decrease with increasing concentration of Tam due to interaction between G4DNA and Tam. This biosensor is a simple and useful tool for selecting G-quadruplex-binding ligands.

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