Carotenoids and related compounds. Part XXI. Structure of neoxanthin (foliaxanthin)

Abstract

Neoxanthin, a universal pigment in green leaves, has been shown to have the allenic structure 5,6-epoxy-3,3′,5′-trihydroxy-6′,7′-didehydro-5,6,5′,6′-tetrahydro-β-carotene (IVa). Samples of lutein (XI), and of zeaxanthin (III), from various natural sources have been compared and their structures have been confirmed. Attempts to isolate taraxanthin, which Curl has suggested may be identical with neoxanthin, yielded the well known epoxide (XIV) of lutein but no carotenoid possessing the O₄ formulation proposed for taraxanthin.