Flavanoids exist as secondary plant metabolites, which displays a wide variety of biological effects. The polymethoxylated flavones, such as nobiletin and tangeretin, present in Citrus reticulata peels are of great interest due to their pharmacological effects. Separation and isolation of these structurally very similar flavones has been achieved by using commercially available ion exchange resins. The strong cation exchange resin [H+] selectively adsorbs the tangeretin and other phenolic compounds present in the matrix in comparison to the hexamethoxylated flavone, i.e. nobiletin. The cation exchange resin can be used successfully to isolate nobiletin and tangeretin from a plant extract. Purity of the isolated compounds was monitored by HPLC using a C-18 column with photometric detection at 280 nm. The structures of the isolated compounds have been confirmed by NMR and tandem mass spectrometry. (C) 2005 Elsevier B.V. All rights reserved.