Three new lignans from Rudbeckia laciniata

Three Rudbeckia species, R. bicolor, R. hirta, and R. laciniata, are wide spread in Korea. Extracts from the plants have been used as traditional Chinese medicine in the treatment of the common cold, and urinary diseases. Various phytochemical constituents, sesquiterpenes, flavonoids, polyacetylenes, and carotenoids have been reported from the genus Rudbeckia and a wide range of biological activities, including antitumor, antioxidant, antibacterial, and antifungal activities were studied. In a continuing search for bioactive constituents from Korean Compositae medicinal plants, we performed a phytochemical investigation of a MeOH extract from the aerial parts of R. laciniata. By repeated column chromatographic separation of the extract three new furofuran lignans (1-3), together with one known lignin (4) were isolated. The identification and structural elucidation of these new compounds were based on 1D and 2D NMR and HR-FABMS data. The cytotoxic activities of the isolated compounds (1-4) were evaluated by determining their inhibitory effects on human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) in vitro using the sulforhodamine B (SRB) assay.