The essential oils of six Helichrysum species from Madagascar were investigated and 46 components were identified by GC, GC-MS and 13 C-NMR spectrometry. The main constituents were 1,8-cineole for H. gymnocephalum (59.7%) and H. bracteiferum (27.3%);ˇ-pinene for H. selaginifolium (38.2%); (E)-caryophyllene for H. cordifolium (55.6%), H. faradifani (34.6%) and H. hypnoides (34.0%).

Background: Malaria is known as tazo or tazomoka in local terminology in Madagascar. Within the context of traditional practice, malaria (and/or malaria symptoms) is commonly treated by decoctions or infusions from bitter plants. One possible approach to the identification of new antimalarial drug candidates is to search for compounds that cure or prevent malaria in plants empirically used to treat malaria. Thus, it is worth documenting the ethnobotanical data, and testing the antiplasmodial activity of the extractive from plants.

Bioassay-guided fractionation of an ethanol extract of a Madagascar collection of the bark of Scutia myrtina led to the isolation of three new anthrone-anthraquinones, scutianthraquinones A, B and C (1-3), one new bisanthrone-anthraquinone, scutianthraquinone D (4), and the known anthraquinone, aloesaponarin I (5). The structures of all compounds were determined using a combination of 1D and 2D NMR experiments, including COSY, HSQC, HMBC, and ROESY sequences, and mass spectrometry. All the isolated compounds were tested against the A2780 human ovarian cancer cell line for antiproliferative activities, and against the chloroquine-resistant Plasmodium falciparum strains Dd2 and FCM29 for antiplasmodial activities. Compounds 1, 2 and 4 showed weak antiproliferative activities against the A2780 ovarian cancer cell line, while compounds 1 – 4 exhibited moderate antiplasmodial activities against P. falciparum Dd2 and compounds 1, 2, and 4 exhibited moderate antiplasmodial activities against P. falciparum FCM29

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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