A new sesquiterpene from South African wild ginger (Siphonochilus aethiopicus (Schweinf) B.L. Burtt).

A new eusdesmane sesquiterpenoid, characterised as 5-acetoxy-9aß-hydroxy-4aαH-3,5α, 8aß-trimethyl-4, 4a, 6, 7, 8a, 9-hexahydronaphtho-([2, 3 b]-dihydrofuran-2-one)-8-one or phaeusmane F acetate (1) has been isolated from the rhizomes of the South African variety of wild ginger (iphonochilus aethiopicus (Schweinf) B.L. Burtt). The compound was obtained after a series of column and gel filtration chromatography. Its structure was elucidated by NMR and Mass-Spectrometric analyses, including 1 D-, 2 D-NMR and HR-LCMS. This is an initial report of the compound from a Siphonochilus sp. Previously isolated similar compounds from the plant material were 4aαH-3,5α,8aß-trimethyl-4,4a,8a,9-tetrahydronaphtho[2,3b]-furan-8-one (siphonochilone) (2), 9aß-hydroxy-4aαH-3,5α,8aß-trimethyl-4,4a,8a,9-tetrahydronaphtho-([2,3b]-dihydrofuran-2-one)-8-one (3), 4aαH-3,5α,8aß-trimethyl-4,4a,8a,9-tetrahydronaphtho-([2,3b]-dihydrofuran-2-one)-8-one (4), 2-hydroxy-4aαH-3,5α,8aß-trimethyl-4,4a,8a,9-tetrahydro-naphtho[2,3b]- furan-8(5H)-one (5), 4aαH-3,5α,8aß-trimethyl-4,4a,8a-trihydronaphtho-([2,3b]-dihydrofuran-2-one)-8-one (6).[Formula: see text].

Two New Antiprotozoal Diterpenes From the Roots of Acacia nilotica.

The powdered roots of the medicinal plant Acacia nilotica were extracted with hexane and ethyl acetate, and the extracts were subjected to column chromatography for the isolation of potentially bioactive compounds and their screening against kinetoplastid pathogens. NMR and HREI mass spectrometric analyses identified two new diterpenes, characterized as 16, 19-dihydroxycassa-12-en-15-one (Sandynone, 1) and (5S, 7R, 8R, 9R, 10S, 13Z, 17S)-7,8:7,17:16,17-triepoxy-7,8-seco-cassa-13-ene (niloticane B, 2). The previously reported (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-diene-7,17-diol (3), (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol-17-al (4), and (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol (5) a, mixture of stigmasterol (6a) and sitosterol (6b), and lupeol (7) were also isolated. Several column fractions displayed significant activity against a panel of Trypanosoma and Leishmania spp., and from the most active fraction, compound 4 was isolated with high purity. The compound displayed high activity, particularly against T. brucei, T. evansi, and L. mexicana (0.88-11.7 µM) but only a modest effect against human embryonic kidney cells and no cross-resistance with the commonly used melaminophenyl arsenical and diamidine classes of trypanocides. The effect of compound 4 against L. mexicana promastigotes was irreversible after a 5-h exposure, leading to the sterilization of the culture between 24 and 48 h.

Antiplasmodial activity of a novel diarylheptanoid from Siphonochilus aethiopicus.

The Nigerian and South African varieties of Siphonochilus aethiopicus were examined for their phytochemical constituents. The ethyl acetate extract of the rhizomes of the South African variety yielded a novel diarylheptanoid, 2,3-diacetoxy-7-(3'',4''-dihydroxy-5''-methoxyphenyl)-1-(4'-hydroxy-3'-methoxyphenyl)-5-heptene and the flavonoid 3,7-dimethoxyquercetin. From the hexane extract of the Nigerian variety, siphonochilone and another flavonoid, 3,4',7-trimethylkaempferol were isolated. The isolated compounds were characterised by NMR spectroscopic techniques and mass spectrometry. The diarylheptanoid was then assayed for antiplasmodial activity in vitro using a Plasmodium falciparum growth inhibition assay. At the concentrations tested, the compound inhibited parasite growth by 69 - 74%, without producing cytotoxic or significant haemolytic effects. The antiplasmodial activity of the compound is likely mediated by direct mechanism(s) in erythrocytic - stage parasites.