One hundred and ninety plants, of which 51 are used to treat malaria in traditional medicine, were collected in five different ecosystems of Madagascar for a screening programme devoted to the search of naturally-occurring antimalarial compounds. Thirty-nine plants, of which 12 are used as herbal antimalarials, were found to display in vitro activity against Plasmodium falciparum with a median inhibitory concentration (IC50) lower than 5 microg/ml while 9 had an IC50 ranging from 5 to 7.5 microg/ml. Seventeen of them exhibited cytotoxic effects on murine P388 leukemia cells with an IC50 < 10 microg/ml. The biological activities were mostly located in the ethyl acetate fractions. Bioassay-directed fractionation is underway to isolate the active constituents.
A species new to science is formally described and named as Clerodendrum kamhyoae Phillipson & L. Allorge. It is the third species of Clerodendrum L. (Lamiaceae) to be described from Madagascar that combines a long slender corolla tube with cauliflory, attributes that are uncommon in the genus. The prolific production of flowers along the trunk of the new species is quite extraordinary. Its possible relationships with other species of the genus are discussed and certain aspects of its reproductive biology are described. We provide line drawings, photographs and a distribution map for the new species, as well as an assessment of its conservation status using IUCN Categories and Criteria.
Catharanthus makayensis L. Allorge, Phillipson & Razakamal. (Apocynaceae), a species new to science from Madagascar is described and illustrated. It differs from all other species in the genus by the hexagonal cross-section of its stems, and by a combination of flowering and fruiting characters. Its 5-6 mm long filiform sepals are clearly much narrower and longer than all other species with the exception of Catharanthus coriaceus Markgr., but the latter species is highly distinct with its pendulous fruits, as opposed to erect fruits of Catharanthus makayensis and all other species of the genus. Catharanthus makayensis and Catharanthus roseus (L.) G. Don are the only species to have a magenta, rather than white to pale yellow eye. The corolla lobes and the flower buds of Catharanthus makayensis are pure white or tinted pale pink whereas Catharanthus roseus typically has pink lobes. The relationships of the new species with the eight other species of Catharanthus G. Don are discussed and an identification key to the Malagasy species of the genus is provided.
Résumé
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