Phytochemical analysis of two Weigela florida cultivars, ``Pink Poppet'' and ``Jean's Gold''

Nine different oleanane-type glycosides were extracted and isolated by various chromatographic methods from two Weigela florida cultivars, ``Pink Poppet'' and ``Jean's Gold''. From the roots of W. florida ``Pink Poppet'', three monodesmosidic oleanolic acid saponins 1, 4, 5 were obtained, together with one hederagenin ester 6 from the leaves, and six bidesmosidic saponins 2,3,6-9 were isolated from the leaves of W. florida ``Jean's Gold''. Among compounds 1-9 , three were previously undescribed (1-3) and six (4-9) were already published in the literature. Their structures were assigned by spectroscopic analysis mainly 2D NMR and mass spectrometry (ESI-MS). The cytotoxicity of the isolated compounds 1,3,4,6,7,9 , against mouse colon carcinoma (CT26), mouse melanoma (B16) and human liver cancer (HepG2) cell lines, was evaluated by MTS assay. The ester group at C-28 and/or the primary alcohol function at C-23 led to a negative effect, whereas monodesmosidic oleanolic acid glycosides displayed a good cytotoxicity with IC 50 ranging from 2.19 to 2.83 mu M. A key sequence in the structure of the molecules was proposed for the cytotoxicity.