Isoflavonoid glycosides from the roots of Baphia bancoensis.

Chemical investigation of the methanol extract of the roots of Baphia bancoensis led to the isolation and characterization of three new isoflavonoid glycosides (1-3). Their structures were determined on the basis of spectroscopic studies andchemical evidence. Antibacterial activity of isolated compounds was evaluated against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa.

Five labdane diterpenoids from the seeds of Aframomum zambesiacum.

Five labdane diterpenoids, (3-5), zambesiacolactone A (7) and zambesiacolactone B (8), were isolated from the seeds of Aframomum zambesiacum (Baker) K. Schum., along with five known labdanes and a linear sesquiterpene, nerolidol. Their structures were elucidated by spectroscopic analysis. Their antiplasmodial activity was evaluated in vitro against Plasmodium falciparum. Compound 3 was the most active with an IC(50) value of 4.97 microM.

Flow Thermolysis Rearrangements in the Indole Alkaloid Series: Strictamine and Akuammicine Derivatives. The Absolute Configurations of Ngouniensine and epi-Ngouniensine.

Flow thermolysis of strictamine (1) generated two of the predictable rearrangement products, resulting from [1,5]-sigmatropic shifts: akuammicine (2) and indolenine 9. Besides formation of these two compounds, a quite different pathway gave rise to a novel rearrangement leading to indole 6, with the framework of the natural alkaloid ngouniensine (19). Rearrangement to the ngouniensine skeleton became the major pathway when the akuammicine derivatives 10, 12, and 17 were submitted to thermolysis, generating compounds 11, 13 + 15, and 18, respectively. These results allowed us to assign the absolute configuration of (-)-ngouniensine (19) (3R,20R) and that of (-)-epingouniensine ((-)-21) (3R,20S).

Four new dammarane saponins from Zizyphus lotus.

Five dammarane-type saponins were isolated by means of centrifugal partition chromatography from the leaves of Zizyphus lotus. Their structures were elucidated using a combination of 1D and 2D 1H and 13C NMR spectra and mass spectroscopy. One of these glycosides is the known jujuboside B (5). Three are new jujubogenin glycosides, identified as 3-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyljujubogenin-20-O-(2,3,4-O-triacetyl)-alpha-L-rhamnopyranoside (1), 3-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyljujubogenin-20-O-alpha-L-rhamnopyranoside (2), and 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[(4-sulfo)-beta-D-glucopyranosyl-(1-->3)]-alpha-L-arabinopyranosyljujubogenin (3). The last is a new sulfated derivative of jujubasaponine IV, identified as 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[(4-sulfo)-beta-D-glucopyranosyl-(1-->3)]-beta-D-galactopyranosyl-(20R,22R)-16beta,22:16alpha,30-diepoxydammar-24-ene-3beta,20-diol (4).

Antiplasmodial activity of alkaloids from various strychnos species.

The in vitro antiplasmodial activities of 69 alkaloids from various Strychnos species were evaluated against chloroquine-resistant and chloroquine-sensitive lines of Plasmodium falciparum. The compounds, comprising mainly indolomonoterpenoid alkaloids, exhibited a wide range of biological potencies in the antiplasmodial assays. The most active alkaloids were also tested for cytotoxicity against HCT-116 colon cancer cells to determine their antiplasmodial selectivity. As a result of these studies, structure-activity relationships for these alkaloids have begun to emerge. Alkaloids presenting four types of bisindole skeleton exhibited potent and selective activities against Plasmodium. They were sungucine-type (IC(50) values ranging from 80 nM to 10 microM), longicaudatine-type (IC(50) values ranging from 0.5 to 10 microM), matopensine-type (IC(50) values ranging from 150 nM to 10 microM), and usambarine-type alkaloids. Within the last structural type, isostrychnopentamine (49) and ochrolifuanine A (46) were found to be active against chloroquine-sensitive and -resistant strains (IC(50) values of 100-150 and 100-500 nM, respectively), and dihydrousambarensine (51) exhibited a 30-fold higher activity against the chloroquine-resistant strain (IC(50) = 32 nM) than against the chloroquine-sensitive one.