Apples contain an anti-inflammatory flavonoid called quercetin, while red wine contains the flavonoid catechin.
It contains 60 % of tanning matter and a large proportion of catechin similar to that contained in gambier, but much redder.
It contains two coloring principles, catechin and catechu-tannic acid.
It contains a crystallisable principle (margosine) and an astringent principle (catechin).
Catechu tannin and catechin are compounds of the catechol tannin type.