Ten highly oxygenated flavonoids, including four new compounds, were
isolated from the leaves of
Dancy tangerine. Six were identified as
5,6,7,3‘,4‘-pentamethoxyflavone (sinensetin) (1),
5,6,7,8,4‘-pentamethoxyflavone (tangeretin) (2),
5,6,7,8,3‘,4‘-hexamethoxyflavone (nobiletin) (3),
5-hydroxy-6,7,3‘,4‘-tetramethoxyflavone (4),
5,7-dihydroxy-6,8,3‘,4‘-tetramethoxyflavone (5), and
5-hydroxy-6,7,8,3‘,4‘-pentamethoxyflavone (5-O-desmethylnobiletin)
(6) by direct comparison with authentic
samples, comparing their spectroscopic data with those reported in the
literature or by simply
interpreting their spectral data. The new compounds were
elucidated as 5,7,8,3‘,4‘- pentamethoxyflavanone (7), 5,6,7,8,3‘,4‘-hexamethoxyflavanone
(8), 7-chloro-3,5,6,8,3‘,4‘-hexamethoxyflavone
(9),
and 7-chloro-3,5,6,8,4‘-pentamethoxyflavone (10) on the
basis of chemical and spectroscopic studies.
Keywords: Citrus; Dancy tangerine leaves; polymethoxyflavone; chloride
polymethoxyflavone;
polymethoxyflavanone