A new flavonoid and other new components from Citrus plants.

A new flavonoid, citflavanone (1), and prenylated phenol derivatives, etrogol (7) and valencic acid (8), were isolated from roots and root barks of Citrus natsudaidai (natsudaidai), C. medica (etrog citron), C. sinensis (valencia orange), and several hybrid seedlings resulting from hyuga-natsu × hirakishu, and characterized. In order to determine the structure of citflavanone (1), prenylation of naringenin (3) was attempted to give 6- and 8-prenylnaringenin (4 and 5, respectively) as well as 6, 8-diprenylnaringenin (6). The location of the prenyl moiety in 4 and 5 was established by means of the long-range selective proton decoupling technique in nuclear magnetic resonance spectrometry.