Cytotoxic constituents from the leaves and stems of Panax quinquefolius.

Four new isolates including one new butanediamide glycoside (1), one new flavonoid glycoside (2) and two new flavonone glycosides (3, 4) were identified from the leaves and stems of Panax quinquefolius, among which 1 possessed the firstly reported N,N'-(5-hydroxy-1,3-phenylene) butanediamide skeleton with an unique 6/9 ranged dual-ring structure. The structures were elucidated by the NMR data, ECD analysis and chemical acid hydrolysis. All the compounds (1-4) were tested for their cytotoxicity against two human cancer cell lines of HepG₂, A549 and HCT116 by the MTT method. Outstandingly, compound 1 exhibited targeted inhibitory proliferation of HCT116 cell with IC₅₀ value of 12.1 μM, whereas compounds 3 and 4 exhibited targeted inhibitory proliferation of HepG₂ cell with IC₅₀ values of 15.3 and 17.3 μM, as well as no obvious cytotoxicity of compounds 1-4 against A549. [ABSTRACT FROM AUTHOR]