Phytochemical analysis of two Weigela florida cultivars, “Pink Poppet” and “Jean’s Gold”

Abstract

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 IC50 ranging from 2.19 to 2.83 μM. A key sequence in the structure of the molecules was proposed for the cytotoxicity.