Carotenoid Composition of Calendula Officinalis Flowers with Identification of the Configuration of 5,8-Epoxy-carotenoids

The carotenoid composition of petals, florets, and full inflorescences of Calendula officinalis grown in sun and shade was investigated by the HPLC-DAD-MS method. The total carotenoid content of flowers grown in the shade was higher than those grown in the sun (1.154 and 0.872 mg/g in petals), while no differences were found in the proportion of individual carotenoids. In all samples, 29 components were identified, from which the main carotenoids, besides lutein, were 5,8-epoxy-carotenoids with 8S and 8 ' R configurations. The main 5,8-epoxy-carotenoid was chrysanthemaxanthin with the 8S configuration and not flavoxanthin with the 8R configuration, as published earlier. In addition, (all-E,8 ' R)- and (9Z,8 ' R)-luteoxanthin were detected in larger amounts. The 5,8-epoxy-carotenoids (flavoxanthin, chrysanthemaxanthin, and luteoxanthin epimers) were also prepared via an acid-catalyzed reaction of the parent carotenoid 5,6-epoxides. The structures of the epimers were elucidated by NMR measurements.