Étude par rm13c d'alcaloïdes à squelette acridinone 9(10h) et pyrido(4,3b) carbazole(6h)

Pyridocarbazole alkaloids from Ochrosia borbonica: lipid-lowering agents inhibit the cell proliferation and adipogenesis of 3T3-L1 adipocyte via intercalating into supercoiled DNA

Bioassay-guided fractionation of an ethanolic extract of Ochrosia borbonica led to the isolation of two known pyridocarbazole alkaloids, ellipticine (1) and 9-methoxyellipticine (2), and six known monoterpenoid indole alkaloids (3-8). Lipid-lowering assay in 3T3-L1 cell model revealed that 1 and 2 could significantly inhibit the lipid droplet formation (EC₅₀ = 0.41 and 0.92 μmol·L^-1, respectively) and lower triglyceride levels by 50%-60% at the concentration of 1 μmol·L^-1, being more potent than the positive drug luteolin (EC₅₀ = 2.63 μmol·L^-1). A mechanistic study indicated that 1 and 2 could intercalate into supercoiled DNA, which consequently inhibited the mitotic clonal expansion of 3T3-L1 cells at the early differentiation phase, leading to the retardance of following adipogenesis and lipogenesis. These findings suggest that 1 and 2 may serve as promising leads for further development of anti-obesity drugs.

Indole and aminoimidazole moieties appear as key structural units in antiplasmodial molecules

From a library of compounds of natural sources, a big series of molecules was chosen by random sampling to evaluate their in vitro antimalarial activity against Plasmodium falciparum and their antifungal activity against Candida sp. From 184 molecules tested, no molecules were active against Candida sp. (MIC>10μg/ml) whereas 13 clearly showed high antiplasmodial activity in vitro, with an IC(50) less than 1μg/ml against the chloroquine-resistant strain of P. falciparum FcM29-Cameroon. The molecules with the best antiplasmodial efficacy were 10-hydroxy-ellipticin (IC(50): 0.08μg/ml), tchibangensin (IC(50): 0.13μg/ml), ellipticin hydrochloride (IC(50): 0.17μg/ml), usambarensin (IC(50): 0.23μg/ml), 7S,3S-ochropposinine oxindole (IC(50): 0.25μg/ml), 3,14-dihydro-ellipticin (IC(50): 0.25μg/ml), tetrahydro-4',5',6'17-usambarensin 17S (IC(50): 0.26μg/ml), ellipticine (IC(50): 0.28μg/ml), aricin (IC(50): 0.3μg/ml), 10-methoxy-ellipticin (IC(50): 0.32μg/ml), aplysinopsin (IC(50): 0.43μg/ml), descarbomethoxydihydrogambirtannin (IC(50): 0.46μg/ml) and ochrolifuanin A (IC(50): 0.47μg/ml). Among these 13 promising molecules, all except descarbomethoxydihydrogambirtannin, ochrolifuanine A and usambarensine presented here novel biological activities since they had never been described in the literature for their antiplasmodial activity. In spite of the large diversity of the molecules which have been tested, it is interesting to note that the ones active against Plasmodium are all indole derivatives (and one is both indolic and aminoimidazolic). To find new antiplasmodial compounds, ethnopharmacological approaches studying traditional medicine treatments for malaria is largely used but random research produced here an interesting yield (7%) of new antiplasmodial hits and appears therefore complementary to the traditional medicine way.

Alkaloids from the Australian rainforest tree Ochrosia moorei

High-throughput screening of a plant and marine invertebrate extract library to find natural products that down-regulate expression of pro-inflammatory genes associated with the glucocorticoid receptor ligand complex led to the identification of bioactive CH2Cl 2 extracts from stems and leaves of the Queensland tree Ochrosia moorei. Bioassay-guided purification of the stem extract enabled the isolation of four alkaloids including two new compounds, ochrosamines A (1) and B (2), and the known compounds ellipticine (3) and 9-methoxyellipticine (4). The leaf extract also afforded 3 and 4 as well as apparicine (5) and desoxycordifoline (6). The structures of the two new compounds were assigned from interpretation of 2D NMR and high-resolution ESIMS data. Ellipticine and 9-methoxyellipticine were the most active components, and both displayed IC 50 values of 90 microM. Apparicine and desoxycordifoline were only very weakly active, and ochrosamines A and B were inactive.

Carbazole alkaloids from Murraya koenigii

Two new alkaloids, 9-carbethoxy-3-methylcarbazole and 9-formyl-3-methylcarbazole, and a known metabolite, 3-methyl-carbazole were isolated from the roots of Murraya koenigii. All three compounds were identified by detailed spectral analyses including 2D NMR studies and their structures confirmed by synthesis. Of the two new metabolites, the 9-formyl compound displayed weak cytotoxicity against both mouse melanoma B16 and adriamycin-resistant P388 mouse leukemia cell lines.