Phenolic antioxidants are ranked by reducing strength and characterized for reversibility using cyclic voltammetry at a glassy carbon electrode. Phenolics with an ortho-diphenol group show a first oxidation peak close to 400 mV (vs. Ag/AgCl) in a model wine solution (12% ethanol, 0.033 M tartaric acid, adjusted to pH 3.6), with a linear concentration dependence below 0.01 mM. Dilution of white wines 10x, and red wines 400x, gave first oxidation peak currents in the 1.5 to 2.2 microA range and 1.9 to 3.4 microC of charge passed by 500 mV, producing values for the concentrations of phenolic antioxidants with low oxidation potentials in the wines. Further peaks in the cyclic voltammograms of the diluted wines correspond to classes of phenolics with higher oxidation potentials, providing a qualitative assessment of wine phenolics based on reducing strength.

As many studies are exploring the association between ingestion of bioactive compounds and decreased risk of non-communicable diseases, the scientific community continues to show considerable interest in these compounds. In addition, as many non-nutrients with putative health benefits are reducing agents, hydrogen donors, singlet oxygen quenchers or metal chelators, measurement of antioxidant activity using in vitro assays has become very popular over recent decades. Measuring concentrations of total phenolics, flavonoids, and other compound (sub)classes using UV/Vis spectrophotometry offers a rapid chemical index, but chromatographic techniques are necessary to establish structure-activity. For bioactive purposes, in vivo models are required or, at the very least, methods that employ distinct mechanisms of action (i.e., single electron transfer, transition metal chelating ability, and hydrogen atom transfer). In this regard, better understanding and application of in vitro screening methods should help design of future research studies on 'bioactive compounds'.

We report the phenomenon of nanosheet rolling during typical aqueous polymerization and study its implications for the self-assembly of polyaniline nanotubes. Specifically, this is done through a detailed morphological and structural characterization of products obtained after 20 min, 1 h in falling pH experiments, and after 20 h at constant pH 2.5 during the oxidative polymerization of aniline with ammonium persulfate in the presence of alanine. The chemical structure has been investigated by FTIR, UV-vis, solidstate 13 C and 15 N NMR, liquid NMR, and XRD, whereas the morphology was imaged using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of self-assembled nanoflakes with different thicknesses ranging from tens to hundreds of nanometers is confirmed through SEM. TEM revealed the presence of very thin layers: nanosheets with sharp and well-defined edges. The presence of hydrogen bonds is confirmed by FTIR and is consistent with XRD results. The stacking of nanosheets and the formation of thicker flakes based on π-π electron interactions have been proposed on the basis of XRD experiments, where self-assembled layers made of cross-linked oxidized aniline structures stack on each other and are stabilized by hydrogen bonds and π-π interactions. In this way, hydrophobic cross-linked oligomers (formed at the beginning of the synthesis at higher pH) minimize their surface energy, self-assembling into well-ordered macromolecular structures. On the basis of the SEM and TEM images and the information obtained from other analytical techniques applied here, the presence of PANI nanotubes formed in the reaction carried out at constant pH of 2.5 is confirmed. The role of the nanosheets in the formation of nanotubes is proposed.

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