Amino acid composition and betaxanthin formation in fruits from Opuntia ficus-indica

In contrast to earlier reports high levels of taurine (2-aminoethanesulfoni c acid) were found in fruit juices of three cultivars of Opuntia ficus-indi ca (L.) Mill. Whereas the occurrence of taurine in plant tissue was thought to be restricted to algae, fungi, and the endosperm of some higher plants, prickly pear proved to be a rich source of dietary taurine. Using L-taurin e as the amino compound, a new betaxanthin was synthesized by partial synth esis. On the basis of chemical and spectral evidence its structure was dete rmined to be the taurine-immonium-conjugate of betalamic acid. Also betalam ic acid could be detected in yellow and orange coloured cultivars of Opunti a ficus-indica for the first time. In spite of the high levels of L-taurine accompanied by the occurrence of betalamic acid, the corresponding betaxan thin could not be detected in the fruit tissue.