Secondary metabolites

Reagents

Reaction indicating that the test is positive

alkaloids

Dragendorff

Precipitate or orange colouring

flavonoids

Cyanidine

Reddish-brown precipitate

polyphenols

Ferric chloride

Heat then pink-orange or purplished colouring

quinones

Bornstraegen

Blackish-blue or green ± dark colouring

saponosides

Foam Test

Persistent foam, higher than 1cm

sterols and polyterpenes

Liebermann

Crimson or purple ring, changing blue then green

tanins

Stiasny

Catechic precipitate in large flakes

Gallic blue-black deep colouring