A Huge PVDF Adsorption Difference Between Resveratrol and ε-Viniferin Allows to Quantitatively Purify Them and to Assess Their Anti-Tyrosinase Property.

Repeated chromatographic analyses of polyphenolic vine stalks extracts allowed us to note a huge adsorption difference on polyvinylidene fluoride (PVDF), between trans-resveratrol 1 and (+)-trans-ε-viniferin 2. We could optimize the conditions (solvent, saturation of the process), for this polymer to adsorb very selectively 2, with regard to the monomer 1 that remains in solution. Since membrane filters made of PVDF are quite often used for HPLC samples filtration, this observation prompted us to inform phytochemists studying plant stilbenoid contents. Based on this background information, we developed a straightforward and inexpensive enrichment process for either 1 and/or 2, from crude Vitis vinifera stalks extracts, allowing to get them in a pure form. Having at hand large amounts of these two pure compounds, they were tested and compared to a set of other relevant molecules for some biological properties: trans-ε-viniferin 2 was shown to be the most powerful tyrosinase inhibitor, among all samples tested.

Novel oligomeric proanthocyanidin derivatives interact with membrane androgen sites and induce regression of hormone-independent prostate cancer.

Prostate cancer is the most common malignancy among men in Western societies, and current therapeutic approaches are evolving to manage growth, recurrence, and mortality neoplasia. Membrane androgen receptors (mARs) have been characterized in human prostate cancer, being preferentially expressed in tumor rather than benign gland areas. Furthermore, mAR agonists (protein-conjugated testosterone) decrease in vitro prostate cancer cell growth and induce apoptosis, whereas in vivo they regress growth of tumor xenografts alone or in combination with taxane drugs. In this respect, targeting mARs might be a novel therapeutic approach in prostate cancer. In our search for new small-molecule ligands of mAR, we report that flavanol dimers B1-B4 (oligomeric procyanidins) decrease in vitro growth of the androgen-sensitive (LnCaP) and androgen-resistant (DU145) human prostate cancer cell lines in the following order: B3 = B4 > B2 ≫ B1 (LnCaP) and B2 ≫ B3 = B4 ≫ B1 (DU145). Some of these analogs were previously shown to trigger signaling cascades similar to testosterone-bovine serum albumin (BSA) conjugate. Galloylation does not confer an additional advantage; however, oleylation increases the dimers' antiproliferative potency by a factor of 100. In addition, we report that B2, oleylated or not, displaces testosterone from mARs with an IC(50) value at the nanomolar range and induces DU145 tumor xenograft regression by 50% (testosterone-BSA 40%). In this respect, oleylated B2 is a potent small-molecule agonist of mAR and could be a novel therapeutic agent for advanced prostate cancer, especially when taking into account the absence of androgenic actions and (liver) toxicity.

Effect of flash release treatment on phenolic extraction and wine composition.

The flash release (FR) process, consisting of rapidly heating the grapes and then applying strong vacuum, has been proposed to increase the polyphenol content of red wines. Its impact on polyphenol extraction kinetics and on the polyphenol composition of red juice and wines was studied over two seasons on different grape varieties (Grenache, Mourvedre, Carignan). The FR process allows fast extraction of all phenolic compounds (hydroxycinnamic acids, flavonols, anthocyanins, catechins, proanthocyanidins) and can be used to produce polyphenol-enriched grape juices. However, the concentration of all polyphenols dramatically decreased throughout fermentation when pressing was achieved immediately after FR. The FR wines made with pomace maceration were also enriched in polyphenols compared to the corresponding control wines. Increasing the duration of high-temperature exposure in the FR treatment further increased extraction of phenolic compounds but also accelerated their conversion to derived species. The tannin-to-anthocyanin ratio was particularly low in the wine fermented in the liquid phase, higher after FR than in the control, and even higher after longer heating. FR resulted in an increased tannin-to-anthocyanin ratio and an increased conversion of anthocyanins to tannin-anthocyanin adducts showing the same color properties as anthocyanins. The tannin-to-anthocyanin ratio was particularly low in the wine fermented in the liquid phase that also contained larger amounts of orange sulfite bleaching-resistant pigments.