Abstract
Herbs have been an integral part of human life for ages. Modern allopathic
drugs had an upper hand over traditional medicine in the past century due to their
mounting inefficacy, resistance, cost, and adverse effects that have led to the reclaim of
herbs once again. Herbs holistically confer biological activity due to the presence of
phytochemicals, which are classified broadly as carbohydrates, lipids, terpenoids,
alkaloids, polyphenols, and essential and volatile oils. In this, polyphenols are a vast
group further comprising flavonoids, phenolic acid, stilbenoids, tannins, lignans,
xanthones, quinones, coumarins, phenylpropanoids, and benzofurans. Of this,
flavonoids are hydroxylated phenolic substances with basic C6-C3-C6 rings
substitution, which gives rise to a series of compounds namely, flavonols, flavanones,
flavones, anthocyanidins, flavanonols, chalcones, isoflavones, and flavanols. They are
abundantly found in vegetables and fruits and exhibit antioxidant, free-radical
scavenging activity, anti-cancer, cardioprotective, anti-diabetic, anti-inflammatory,
anti-allergic, and anti-microbial action. The advent of modern molecular techniques
and computational methodologies has thrown light on the molecular mechanism of
action of these flavonoids, which was otherwise obscure. Hence this chapter aims to
review the types, sources, chemistry, and molecular mechanisms of action of the
various phytomolecules of flavonoid groups.