The polyphenols found in grapes are highly diverse compounds and can be broadly classified into four groups:

	Phenolic acids (e.g. gallic acid)
	Anthocyanins (pigments, e.g. malvidin 3-glucoside)
	Simple flavonoids
	Complex flavonoids (proanthocyanidins)

Around 90% of polyphenols are not extracted from the wine making process. The majority remains within the grape skins and seeds and lost from the winery with the marc.

	Grape seed
		60% of extractable grape polyphenols
		Mainly proanthocyanidins (monomeric flavan-3-ols, especially (+)-catechin, (-)-epicatechin, (+/-) gallocatechin, (-)-epicatechin 3-0-gallate; and their oligomers and polymers)
	Grape skin
		30% of extractable grape polyphenols
		Mainly pigmented tannins (flavonoids)
		Resveratrol
	Grape pulp
		Less than 10% of total extractable grape polyphenols