Green Chemistry Approaches to the Synthesis of Flavonoids

In nature, flavonoids constitute a relatively diverse family of aromatic molecules such as flavones, flavonols, flavanones, isoflavone, chalcones, and their derivatives. Natural and synthetic flavonoids have reported diverse biological activity including antimycobacterial, antimicrobial, antiproliferative, antiarrhythmic, antiviral, antihypertensive, antioxidant, and anti-inflammatory. Flavonoids have garnered much attention as potential targets for nutraceuticals and pharmaceuticals. The recent development of ‘‘Green Chemistry’’ has enabled us to manipulate biosynthetic pathways to generate a library of synthetic flavonoids and to diminish the hazards for human health and environmental pollution from conventional methods. This paper presents an exhaustive review of the green synthesis of flavonoids. Green chemistry is the need for the day; hence chalcones can be synthesized in an eco-friendly manner without using solvents. The chalcone synthesis involves the solvent-free solid-state trituration between acetophenone derivatives and substituted benzaldehydes in the presence of NaOH/KOH as a base (Claisen-Schmidt reaction). Using these chalcone derivatives, synthesis of flavonoids can be done. In the pharmaceutical arena, economical bulk production of different types of flavonoids has been successfully established by green chemistry techniques.