| Abstract: | Valencia orange (C. sinensis) and Robinson tangerine [(C. paradisi × C. reticulata) × (C. reticulata)] were examined for flavonoids. Thirteen flavonoids were isolated, six of which are new constituents of citrus peel. These are: 3,5,6,7,3′,4′-hexamethoxyflavone, 3,5,7,8,3′,4′-hexamethoxyflavone, 5-hydroxy-3,7,8,3′,4′-pentamethoxyflavone, 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone, 5,7,8,4′-tetramethoxyflavone and 5,7,8,3′,4′-pentamethoxyflavone. The latter three flavonoids are reported for the first time as natural products. A method is described for readily obtaining small quantities of 5,7,8,4′-tetramethoxy and 5,7,8,3′,4′-pentamethoxyflavones from their 5,6,7-trimethoxy analogs. |
