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Betalains

Betalains get their name from red beets (the genus Beta in the Chenopodiaceae), which are red in color due to the presence of the betalain. Certain betalains are responsible for the reddish flowers in another favorite holiday plant, the Christmas Cactus (Schlumbergera bridgesii). The discovery of betalains in cacti helped taxonomists understand the phylogenetic position of the Cactus family or Cactaceae. The Cactaceae were once classified in their own order near the carrot family (Apiaceae), but now the family is placed in a very different order, the Caryophyllales, along with the only other betalain-producing angiosperm families such as: Achatocarpaceae, Aizoaceae (with ice plants), Amaranthaceae, Basellaceae, Chenopodiaceae (with red beets and saltbushes), Didieriaceae, Nyctaginaceae (with Bougainvillea), Phytolaccaceae (with Pokeweed), and Portulacaceae.

Betalains are synthesised by a long chemical process from a common amino acid called tyrosine, the first step being the manufacture of L-Dopa (found in the animal brain - responsible for movement and mood) as above in alkaloids.

Betalains are a chemotaxonomically important group of water-soluble chromoalkaloids (red-violet betacyanins and yellow betaxanthins), which occur only in certain members of the plant order Caryophyllales (e. g. red beet) and some higher fungi (e. g. fly agaric).

 

  • Betalains are alkaloid pigments that are found in some families of plants belonging to the order Caryophyllales, but in no other plants.

  • Betalains are not found in plants containing anthocyanin pigments. Structurally they are unrelated
  • They have also been found in some fungi
  • They can be divided into betacyanins and betaxanthins based upon their molecular structure.
  • betacyanins generally appear red to red violet in colour
  • betaxanthins generally appear yellow in colour
  • They cause colour in both flowers, fruits and sometimes vegetative organs
  • They are found in the vacuole
  • They are aqueous in solubility
  • Betacyanins absorb in the 535-550nm range
  • Betaxanthins absorb in the 475-480nm range
  • Beetroot contains 2 Betacyanins Betanin and a derivative
  • Little is known about the role of betalains but it is thought they may protect against pathogens

The basic structure of betacyanins

Betalains are synthesized from the amino acid tyrosine through L-DOPA into the two subclasses, betacyanins (reds and purples) and betaxanthins (yellows).