Fisetin is a flavonol, a structurally distinct chemical substance that belongs to the flavonoid group of polyphenols. It can be
found in many plants, where it serves as a colouring agent. Its chemical formula was first described by Austrian chemist Josef
Herzig in 1891.

Fisetin can be found in various plants such as Acacia greggii, Acacia berlandieri, in the yellow dye young fustic from Rhus
cotinus (Eurasian smoketree), in Butea frondosa (parrot tree), Gleditschia triacanthos, Quebracho colorado and the genus Rhus and
in Callitropsis nootkatensis (yellow cypresses). It is also reported in mangoes