Quercetin is a secondary metabolite that is mainly present in the boundary layers of plants in order to protect them against antioxidant influences (e.g. oxygen radicals).
Quercetin is the most frequently occurring flavonoid and belongs to the subcategory of flavonols, which are characterized by their bright yellow color (Latin flavus = yellow).
Like all flavonoids, quercetin has antioxidative and antimicrobial effects. However, the content of quercetin decreases to zero when the shell / skin of fruits or vegetables is removed. For example, the shell of the quince has a quercetin content of 180 mg / kg fresh weight, pure pulp contains only trace amounts of quercetin.
Content of quercetin in foods
(in mg/kg fresh weight)
Hertog et al. 1992
Books on Amazon
- Food Chemistry by H.-D. Belitz
- Plant Secondary Metabolites: Occurrence, Structure and Role in the Human Diet
- Plant Secondary Metabolites (Methods in Molecular Biology)
- Biotechnology: Secondary Metabolites