Preparation, stereochemistry, and cytotoxic activity of the melampolides from Mikania minima

2α-Acetoxy-15-acetylartemisiifolin, a new Anti-trypanosomal Sesquiterpene Lactone from Mikania guaco

Mikania guaco Bonpl. methanol extract showed an interesting activity against Trypanosoma cruzi with an IC50 of 4 μg/mL. Bioassay-guided fractionation of the methanol extract resulted in the isolation of a new sesquiterpene lactone, 2α-acetoxy, 15-acetylartemisiifolin (1), which was shown to be active (IC50 = 25 μM) against the amastigote form of T. cruzi,. The chemical structure of 1 was elucidated using 2-D NMR techniques and mass spectrometry.

Sesquiterpene lactones from Mikania micrantha and Mikania cordifolia and their cytotoxic and anti-inflammatory evaluation

The guaianolide 8-epi-mikanokryptin (1) and the melampolide 11Hβ-11,13-dihydromicrantholide (2) along with known sesquiterpene lactones (3-13) and other constituents were isolated from the aerial parts of different populations of Mikania micrantha and Mikania cordifolia collected in several states of Mexico. The relative and absolute configurations of 1 were determined by X-ray diffraction and CD analysis, respectively. Considering the (1)H and (13)C NMR chemical shift similarities and the H-H coupling constant values, a [(1)D(14), (15)D5] conformation was established for micrantholides (2, 8-13). We tested nearly all the sesquiterpene lactones for antiproliferative activity in human cancer cell lines, and they exhibited moderate activity. Additionally, in a mouse ear model of edema induced by TPA, the anti-inflammatory activities were marginal.

Antiviral constituents against respiratory viruses from Mikania micrantha

Phytochemical investigation of the dried aerial parts of Mikania micrantha led to the isolation of a new sesquiterpene, 3beta-acetoxy-1,10-epoxy-4-germacrene-12,8;15,6-diolide (1), along with six known constituents: 1,10-epoxy-4-germacrene-12,8;15,6-diolide (2), dihydromikanolide (3), potassium mikanin 3-sulfate (4), mikanin (5), alpinetin (6), and ergosta-7,22-dien-3beta-ol (7). Their structures were elucidated by spectroscopic methods, and the molecular structures and stereochemistry of sesquiterpene lactones 1-3 were revealed by single-crystal X-ray analysis. Compound 2 showed moderate activity against respiratory syncytial virus (IC(50) = 37.4 uM) and parainfluenza type 3 virus (IC(50) = 37.4 uM) with a therapeutic index (TI) of 16.0 for both compounds. Compound 4, the main component of M. micrantha, exhibited inhibitory activity against parainfluenza type 3 virus with IC(50) (19.7 uM) and TI (24.0) values comparable to those of ribavirin, serving as a positive control.

NMR spectroscopic, mass spectroscopic, X-ray crystallographic, and theoretical studies of molecular mechanics of natural products: farformolide B and sesamin

Two natural products, farformolide B and sesamin were isolated from Farfugium japonicum and Cinnamomum kanehirae, respectively. The structures of the two natural products, including their relative stereochemistry, were elucidated using spectroscopic data and theoretical calculations. The molecule 1 (farformolide B) is newly recognized by X-ray crystallography. The two compounds were also investigated by a theoretical analysis using the B3LYP/6-31G* method of the Gaussian 03 package program. The theoretical results were supplemented by experimental data to determine the optimal geometric structures of the two compounds. The calculated molecular mechanics were found to compare well with the experimental data. Several important thermodynamic properties of the two products, including ionization potentials, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, energy gaps, heat of formation, atomization energies, and vibration frequencies, were also calculated. The study also provided a good understanding of the stereochemical structure and thermodynamic properties of the two molecules.

Synthesis of (+)-8-deoxyvernolepin and its 11,13-dihydroderivative. A novel reaction initiated by sulfene elimination leads to the 2-Oxa-cis-decalin skeleton

The title compounds are interesting candidates for antifungal screening. This paper describes the enantiospecific synthesis of these compounds starting from (+)-costunolide isolated from a commercially available extract. We used two novel reactions as key synthetic steps in this work: the acid-induced cyclization of an delta,epsilon-epoxy ester, which stereoselectively gave a hydroxymethyl-substituted delta-lactone, with the hydroxyalkyl group in the desired beta-equatorial disposition, and a reaction cascade, initiated by a base-promoted sulfene elimination, which led to a 10-oxiranyl-2-oxa-cis-decalin from the mesylate of a trans-fused delta-lactone. We also found that the reaction between selenium dioxide and the 1,5-diene system of elemanolides gave selenadecalins analogous to natural eudesmanolides. Our results prove that the synthetic strategy employed, on the basis of biomimetic concepts, is a useful procedure for the enantiospecific preparation of (+)-vernolepin-related compounds from accessible germacrolides.