Cytotoxic diterpenoids from Podocarpus madagascariensis from the Madagascar rainforest.

Bioassay-directed fractionation of an extract of the root and bark of Podocarpus madagascariensis resulted in the isolation of a new totarol diterpenoid (1) in addition to the three known cytotoxic diterpenoids 19-hydroxytotarol (2), totaradiol (3), and 4beta-carboxy-19-nor-totarol (4). The structure of the new compound 1 was established as methyl-13-hydroxy-14-isopropyl-9(11),12,14(8)-podocarpatriene-19-oate on the basis of 1D and 2D NMR spectroscopic interpretation and methylation of 4. All the compounds exhibited cytotoxic activity against the A2780 ovarian cancer cell line.

Ipomoeassins A-E, cytotoxic macrocyclic glycoresins from the leaves of Ipomoea squamosa from the Suriname rainforest.

The new glycoresins, ipomoeassins A-E (1-5), have been isolated from the leaves of Ipomoea squamosa. The structures were elucidated by spectroscopic analyses and chemical transformations. The absolute configurations of C-5 (ipomoeassins 3-5) and C-11 (ipomoeassins 1 and 2) were determined by their derivatives with (R)- and (S)-MPA. All the isolates were active in the A2780 human ovarian cancer cell line assay, and 4 showed the highest activity with an IC(50) value of 35 nM.

The bioactive Taxol conformation on beta-tubulin: experimental evidence from highly active constrained analogs.

The important anticancer drug Taxol (paclitaxel) binds to tubulin in a stoichiometric ratio and promotes its assembly into microtubules. The conformation of microtubule-bound drug has been the subject of intense study, and various suggestions have been made. In this work we present experimental and theoretical evidence that Taxol adopts a T-shaped conformation when it is bound to tubulin.

Shared ectomycorrhizal fungi between a herbaceous perennial (Helianthemum bicknellii) and oak (Quercus) seedlings.

• Ectomycorrhizal infection of Quercus seedlings can be low at a distance from established ectomycorrhizal vegetation. Here we investigate whether Helianthemum bicknellii, a herbaceous ectomycorrhizal perennial of prairies and oak savannas, creates patches of elevated ectomycorrhizal infection of Quercus seedlings. • We performed two studies. First, ectomycorrhizas of H. bicknellii were compared with ectomycorrhizas of Quercus spp. Second, soil bioassays were conducted with Quercus macrocarpa seedlings grown in soils from near H. bicknellii; near established Quercus spp.; or distant from ectomycorrhizal vegetation. • Eight species associated with H. bicknellii were identified: Cenococcum geophilum, Russula aff. amoenolens, an unknown Pezizalean fungus, Laccaria laccata, Tomentella sp., Lactarius mutabilis, Russula aff. pectinatoides, and Cortinarius sp. Internal transcribed spacer restriction fragment length polymorphism (ITS RFLP) patterns of all species except Cortinarius sp. matched to ectomycorrhiza from Quercus. In the bioassay, ectomycorrhizal infection was higher in near-Helianthemum soils than in distant soils, but lower than in near-Quercus soils. • These results demonstrate that H. bicknellii, a common herbaceous plant of oak savannas, shares ectomycorrhizal partners with Quercus and provides patches of increased ectomycorrhizal infection of Quercus seedlings.