Flavonoids are a widespread family of phytochemicals with
diverse biological functions in plants. Their analysis has increased
due to their recognized physiological actions in humans. Numerous
studies relate the ingestion of polyphenols on diet to a lower risk
of cardiovascular diseases and development of cancers [1]. Apart
from their beneficial properties which have conferred to them a
relevant role in foods as nutraceuticals [2], polyphenols are chemotaxonomic
markers due to their specificity and ubiquity, and they
have proven to be chemical markers for food authentication [3–5].
Polyphenols exhibit a huge variety of structures in nature. Phenolic
acids, divided into two groups: hydroxybenzoic acids with
C6–C1 structures and hydroxycinnamic acids with C6–C3 squeleton,
and flavonoids, formed by a series of condensation reactions
between a hydroxycinnamic acid (B-ring and carbon atoms 2, 3
and 4 of C-ring) and malonyl residues (A-ring), giving rise to a
C6–C3–C6 base structure (Fig. 1). In plants, flavonoids may occur
in various modified forms corresponding to additional hydroxyla-