Qualitative and quantitative aspects of betalains biosynthesis in Amaranthus caudatus L. var. pendula seedlings

Seedlings of Amaranthus caudatus L. var. Pendula were used to study the influence of several treatment: white light, 3,4-dihydroxyphenylalanine (DOPA), kinetin, gibberellic acid (GA₃) on betalains biosynthesis. The pigments, betacyanins and betaxanthins, were separated using a Sephadex G-15 column chromatography. Qualitative as well as quantitative differences were observed according to the treatments applied.The amaranthin biosynthesis seemed to be favored in the absence of DOPA. Under the combined effect of kinetin and white light a small quantity of betanin was also synthesized. Adding exogenous DOPA led to a more diversified production which included betacyanins (amaranthin and betanin), betaxanthins (vulgaxanthin and miraxanthin), and even dopachrome. As a general rule, kinetin activated the betalains biosynthesis whereas GA₃ inhibited it. The stimulating effect of white light was always much greater than that of kinetin.Abbreviations GA₃ gibberellic acid - GA₄ gibberellin 4 - BHT 2,6-diter-butyl-4-methylphenol - DOPA 3,4-dihydroxyphenylalanine - Kinetin 6-furfurylaminopurine