Abstract
Flavonoids are widely distributed in vascular plants and mosses. The basic structure consists of a fifteen-carbon skeleton, i.e. two phenyl rings (A- and B- rings) connected by a three-carbon (C-ring). Flavonoids are substituted with hydroxyl, methoxyl and/or glycosyl groups in various combinations. Moreover, aromatic and aliphatic acids are sometimes attached. About 10,000 kinds of flavonoids have been reported as natural compounds. The functions of flavonoids in living plants are also known well, e.g. pollinator attractants, oviposition stimulants, defensive agents, allelopathy, phytoalexins, etc.
‘Flavonoid Collection’ is a collection of authentic flavonoids isolated from various plants and is stored in the National Museum of Nature and Science, Japan. About 1,000 samples, especially flavonoids, are preserved. In this paper, we describe our research, including utilization of authentic specimens, from which we identified small amounts of flavonoids and reconstructed the blue color of Dutch Iris (Iris × hollandica) flowers. We characterized 17 C-glycosylflavones and an anthocyanin in the flowers of Dutch Iris, using some authentic specimens. Furthermore, we explored the intermolecular copigmentation in the blue flower of Dutch Iris by in vitro reconstruction using the isolated anthocyanin and C-glycosylflavone.
The research using authentic specimens enabled us to accelerate the identification of flavonoids. We plan to re-identify the stored ‘Flavonoid Collection’ using more modern analytical techniques and to construct an online database for further development of flavonoid research and related fields.
