Possible Clues:

• The girl in the can is yellow and acid
• There's something in red wine that takes a lot of beating
• Compound from bark or tea, used for dyeing
• Chemical compound in e.g. tea
• Substance found in red wine and used in dyeing
• It gives red wine an astringent taste
• It gives red wine its color
• Something in red wines
• Bitter substance in wine
• Substance used in leather production