Betalains are the yellow and violet pigments that substitute
anthocyanins in plants belonging to the order Caryophyllales.
These pigments have attracted much
attention because of their bioactivities, which range from
an antioxidant capacity to the chemoprevention of cancer.
However, the biosynthetic pathway of betalains
remains under discussion; the main steps have been
characterized in recent years, but multiple side reactions
arepossible.The key enzymes involvedhaveonly recently
been described, providing clues about the regulation of
betalain biosynthesis. In this review, we provide a comprehensive
view of the biosynthetic scheme of betalains
and discuss the different reactions that have been demonstrated
experimentally or proposed in the literature