Investigation of the endemic Malagasy plant Bussea sakalava Du Puy & R. Rabev. (Fabaceae) for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of the four new diphenylpropanes 1-4 and the new cycloheptadibenzofuran 5; compound 5 has a previously unreported natural product skeleton. The structure elucidation of these compounds was based on the analysis of their 1D and 2D NMR and mass spectroscopic data. Compounds 1-5 were tested for antiproliferative activity against the A2780 human ovarian cancer cell line.In our continuing search for biologically active natural products from tropical rainforests as part of an International Cooperative Biodiversity Group (ICBG) program, we obtained an ethanol extract from the roots of a plant identified as Bussea sakalava Du Puy & R. Rabev. (Fabaceae) from Madagascar. This extract showed moderate antiproliferative activity against the A2780 human ovarian cancer cell line with an IC 50 value of 10 µg/mL. The extract was selected for examination on the basis of this activity and the absence of previous phytochemical studies of the species.Previous studies on the genus Bussea indicated the presence of azetidine-2-carboxylic acid and 3-hydroxyproline in seeds of different Bussea species,2 , 3 and the cytotoxicity and high trypanocidal activity of a methanol extract of stem bark of Bussea occidentalis has been reported.4Fractionation of a dichloromethane fraction of an ethanol extract of B. sakalava by C-18 open column and high performance liquid chromatography (HPLC) yielded four new diphenylpropanes named bussealins A-D (1 -4) and a cycloheptadibenzofuran derivative named bussealin E (5). Herein we report the structural elucidation of these new compounds and their antiproliferative properties against the A2780 human ovarian cancer cell line.* To whom correspondence should be addressed. Tel: (540) (Table 1) and were consistent with the molecular formula. The above data suggested that 1 had a diphenyl propane skeleton. The complete 1 H and 13 C NMR assignments and the connectivities were determined from analysis of a combination of COSY, HMQC, and HMBC data. Three mutually coupled methylene groups were revealed by the cross peaks observed in the COSY spectrum. In the HMBC spectrum, H-1 (δ H 2.41) showed correlations with C-2 (δ C 33.0), C-3 (δ C 30.6), C-1' (δ C 140.2), and with C-2' and C-6', both of which had the same chemical shifts (δ C 108.7). The A 2 substitution pattern of the A ring of 1 was established by HMBC correlations from the signal at δ H 6.18 (H-2' and H-6') to C-1 (δ C 36.5), C-1' (δ C 140.2), C-3' (δ C 151.3), C-4' (δ C 134.7) and C-6' and C-2' (δ C 108.7), as well as the correlation from one OCH 3 group at δ H 3.75 to C-4' (δ C 134.7). The proton substitutions on the B ring were assigned based on the 3 J HMBC correlations between H-3 (δ H 2.52) and C-6" (δ C 120.5), and between H-5" (δ H 6.38) and C-1" (δ C 123.4). Moreover, the H-5" proton showed HMBC correlations to C-6" (δ C 120.5), C-4" (δ C 147.8) and C-3" ...

Melicope madagascariensis (Rutaceae) is an endemic plant species of Madagascar that was first classified as a member of the genus Euodia J. R. & G. Forst (Rutaceae) under the scientific name Euodia madagascariensis Baker. Based on morphological characteristics, Thomas Gordon Hartley taxonomically revised E. madagascariensis Baker to be M. madagascariensis (Baker) T.G. Hartley. Chemotaxonomical studies have long been used to help the identification and confirmation of taxonomical classification of plant species and botanicals. Aiming to find more evidences to support the taxonomical revision performed on E. madagascariensis, we carried out phytochemical investigation of two samples of the plant. Fractionation of the ethanol extracts prepared from two stem bark samples of M. madagascariensis (Baker) T.G. Hartley led to the isolation of seven known furoquinoline alkaloids 1–7 and two known methoxyflavones 8 and 9. The presence of furoquinoline alkaloids and methoxyflavones in the title species is in agreement with its taxonomic transfer from Euodia to Melicope. Antiprotozoal evaluation of the isolated compounds showed that 6-methoxy-7-hydroxydictamnine (heliparvifoline, 3) showed weak antimalarial activity (IC50 = 35 µM) against the chloroquine-resistant strain Dd2 of Plasmodium falciparum. Skimmianine (4) displayed moderate cytotoxicity with IC50 value of 1.5 µM against HT-29 colon cancer cell line whereas 3,5-dihydroxy-3′,4′,7-trimethoxyflavone (9) was weakly active in the same assay (IC50 = 13.9 µM).Graphical Abstract

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Investigation of the endemic Madagascar plant Leptadenia madagascariensis Decne. (Apocynaceae) for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of the four new cardenolides 1-4. The structure elucidations of these compounds were based on analyses of their 1D and 2D NMR spectra and mass spectrometric data. The cardenolides were strongly antiproliferative to the A2780 ovarian cancer cell line, with IC 50 values of 0.18, 0.21, 0.17 and 0.29 μM line, and to the H460 human lung cancer cell line, with IC 50 values of 0.16, 0.68, 0.37 and 0.48 μM respectively.

Investigation of the endemic Madagascan plant Uvaria sp. for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of two new acetogenins. The structures of these two compounds were elucidated based on analysis of their 1D and 2D NMR spectra, circular dichroism and mass spectrometric data, together with chemical modification. The two acetogenins display weak antiproliferative activity against the A2780 ovarian cancer, the A2058 melanoma, and the H522 lung cancer cell lines.