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International audience; Gallotannins extracted from gallnuts are commonly added to wine to improve its properties. They consist of mixtures of galloylester derivatives of glucose. However, their composition and properties are not well-established. In this study, methods based on liquid chromatography coupled to ultraviolet–visible detection and mass spectrometry, size-exclusion chromatography, and one-dimensional (31P) and two-dimensional (1H diffusion ordered spectroscopy, 31P total correlated spectroscopy, and 1H/13C heteronuclear single-quantum correlation and heteronuclear multiple-bond correlation) nuclear magnetic resonance spectroscopies have been implemented for extensive chemical characterization of three commercial gallnut tannin extracts. Differences in the proportions of the different constituents (gallic, digallic, and trigallic acids and galloylglucose derivatives) and in the structure and molecular weight distributions of gallotannins were demonstrated between the three extracts, with chains containing 8.5, 12.2, and 12.4 galloyl groups on average for TAN A, TAN B1, and TAN B2, respectively. The antioxidant capacities of the extracts, evaluated using the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method, were similar and related mostly to their total tannin content, with only a limited impact of the tannin composition.

vitamin E; tocopherol succinate; gap junction; connexin 43; liver cells; International audience; Vitamin E is a scavenger molecule trapping free radicals in biological membranes. However, it has also been shown to elicit the formation of reactive oxygen species and apoptosis in cancer cells. In this study, we tested the ability of alpha-tocopherol, tocopherol acetate, tocopherol phosphate and tocopherol succinate (TS) to modulate gap junctional intercellular communication in the rat liver epithelial cell line IAR203, as measured by the transfer of Lucifer yellow. While alpha-tocopherol, tocopherol acetate and tocopherol phosphate moderately reduced the dye transfer, TS at 10 and 25 microM strongly inhibited it, probably via the induction of the hypophosphorylation of connexin 43. Our results show that, besides their interesting antioxidant properties, vitamin E analogs, especially TS, can exert adverse effects on gap junctional intercellular communication, which could explain their controversial effects in carcinogenesis.

The genotoxicity of diesel particles has been widely documented, and their tumor promoting effect has been reported recently using the gap junction intercellular communication (GJIC) assay. In the study, the ability of soluble organic fractions (SOF) of diesel particles emitted from cars equipped (WC) or not (WoutC) with the oxidation catalytic converter (OCC) and of particle SOF from an outdoor high polluted place (OHPP) to inhibit GJIC has been evaluated with two cell lines: a rat liver epithelial cell line (REL cells) and a rat pulmonary alveolar type II cell line (3T cells). With both cell lines, the results demonstrate that GJIC is strongly inhibited by WoutC, whereas it is much less reduced by WC ones: for REL cells, the activity of WC particles is 1/4 off the one of WoutC. Also, the authors show that the inhibition induced by WoutC is associated with a change in the GJ protein localization. Their results clearly show the effectiveness of the OCC technology in reducing both the tumor promoting activity and the genotoxicity of diesel particle SOF. (A)