Bioactive Polymethoxyflavones and Flavanone Glycosides from the Peels of Citrus Deliciosa

Six biologically active flavonoids were isolated from the fruit peels of Citrus deliciosa. Analysis off their spectral data (UV, MS, 1H, 13C and 2D NMR experiments) confirmed their structures as four polymethoxyflavones (5-0-demethylnobiletin 1; tangeritin 2; nobiletin 3 and 5,7,8,3’,4’-pentamethoxyflavone 4) as well as two flavanone glycosides (hesperetin-7-0-glucoside 5 and hesperidin 6). The IH NMR assignment of3 and the isolation of 5 from Rutaceae is reported for the first time. The isolated flavonoids displayed antibacterial activities against a series of G +ve and G –ve bacteria. The chemotaxonomic value of the present findings has been verified, and some of the isolated flavonoids may provide good markers for chemotaxonomical studies of Citrus species.