Highly Galloylated Tannin Fractions from Witch Hazel (Hamamelis virginiana) Bark: Electron Transfer Capacity, In Vitro Antioxidant Activity, and Effects on Skin-Related Cells

• Published in: Chemical research in toxicology Vol. 21; no. 3; pp. 696 - 704
• Main Authors: Touriño, Sonia, Lizárraga, Daneida, Carreras, Anna, Lorenzo, Sonia, Ugartondo, Vanessa, Mitjans, Montserrat, Vinardell, María Pilar, Juliá, Luis, Cascante, Marta, Torres, Josep Lluís
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.03.2008
• Subjects: 3T3 Cells; Amidines - blood; Animals; Antineoplastic Agents, Phytogenic - pharmacology; Antioxidants - pharmacology; Biphenyl Compounds; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Survival - drug effects; Chromatography, High Pressure Liquid; Cysteamine - chemistry; Electron Transport - drug effects; Erythrocytes - drug effects; Fibroblasts - drug effects; Gallic Acid - chemistry; Hamamelis - chemistry; Hamamelis virginiana; Humans; Keratinocytes - drug effects; Magnetic Resonance Spectroscopy; Melanoma - drug therapy; Melanoma - pathology; Mice; Picrates - chemistry; Plant Bark - chemistry; Skin - cytology; Skin - drug effects; Skin - radiation effects; Solvents; Sulfhydryl Compounds - chemistry; Tannins - pharmacology; Vitaceae
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx700425n

Witch hazel (Hammamelis virginiana) bark is a rich source of both condensed and hydrolizable oligomeric tannins. From a polyphenolic extract soluble in both ethyl acetate and water, we have generated fractions rich in pyrogallol-containing polyphenols (proanthocyanidins, gallotannins, and gallates). The mixtures were highly active as free radical scavengers against ABTS, DPPH (hydrogen donation and electron transfer), and HNTTM (electron transfer). They were also able to reduce the newly introduced TNPTM radical, meaning that they included some highly reactive components. Witch hazel phenolics protected red blood cells from free radical-induced hemolysis and were mildly cytotoxic to 3T3 fibroblasts and HaCat keratinocytes. They also inhibited the proliferation of tumoral SK-Mel 28 melanoma cells at lower concentrations than grape and pine procyanidins. The high content in pyrogallol moieties may be behind the effect of witch hazel phenolics on skin cells. Because the most cytotoxic and antiproliferative mixtures were also the most efficient as electron transfer agents, we hypothesize that the final putative antioxidant effect of polyphenols may be in part attributed to the stimulation of defense systems by mild prooxidant challenges provided by reactive oxygen species generated through redox cycling.