A New Anthraquinone from the Root of Cassia fistula and Their Antitobacco Mosaic Virus Activity

The plant of Cassia fistula L., (Leguminosae) can be found in various countries in Asia, South Africa, Mexico, China, West Indies, East Africa and Brazil 1 .In China, it has been widely used as traditional Chinese medicine for treatment of diarrhea, gastritis, ringworm and fungal skin infections 2 .Previous phytochemical studies of C. fistula have shown the presence of anthraquinones 3 , steroids 4 , chromones 5,6 and flavonoids 7 .Continuing the efforts to discover bioactive metabolites from local plants, we now investigated the chemical constituents of the root of C. fistula, leading to the isolation of a new anthraquinone (1) (Fig. 1).The structures of the isolated compounds were determined by means of spectroscopic methods including 1D and 2D NMR techniques and compounds 1 exhibited modest in vitro antitobacco mosaic virus activity.UV spectra were obtained using a Shimadzu UV-2401A spectrophotometer.IR spectra were obtained in KBr disc on a Bio-Rad Wininfmred spectrophotometer.ESI-MS were measured on a VG Auto Spec-3000 MS spectrometer. 1 H, 13 C and 2D NMR spectra were recorded on Bruker DRX-500 instrument with TMS as internal standard.Column chromatography was performed on silica gel (200-300 mesh), or on silica gel H (10-40 µm, Qingdao Marine Chemical Inc., China).Preparative HPLC was used an Agilent 1100 HPLC equipped with ZORBAX-C18 (21.2 mm × 250 mm, 7.0 µm) column and DAD detector.The roots of Cassia fistula L., (Leguminosae) were collected on Dehong Prefecture, Yunnan Province, P.R. China, in