Parametric sensitivity analysis for the helium dimers on a model potential

Potential parameters sensitivity analysis for helium unlike molecules, HeNe, HeAr, HeKr and HeXe is the subject of this work. Number of bound states these rare gas dimers can support, for different angular momentum, will be presented and discussed. The variable phase method, together with the Levinson's theorem, is used to explore the quantum scattering process at very low collision energy using the Tang and Toennies potential. These diatomic dimers can support a bound state even for relative angular momentum equal to five, as in HeXe. Vibrational excited states, with zero angular momentum, are also possible for HeKr and HeXe. Results from sensitive analysis will give acceptable order of magnitude on potentials parameters.

Evaluation of antimicrobial activity and toxic potential of extracts and triterpenes isolated from Maytenus imbricata

The phytochemical study of hexane/ethyl ether (1:1) extract of the roots of M. imbricata, Celastraceae, resulted in the isolation and characterization of six known triterpenes: 11α-hydroxylup-20(29)-en-3-one, previously isolated from this species besides, 3β,11α-di-hydroxylup-20(29)-ene, 3,7-dioxofriedelane, 3-oxo-29-hydroxyfriedelane, tingenone and 6-oxo-tingenol. The chemical structures of these triterpenes were established by spectrometric data (IR, ¹H and 13C NMR) and through comparison with literature data. The hexane/ethyl ether (1:1), ethyl acetate and methanol extracts, and 11α-hydroxylup-20(29)-en-3-one, tingenone and 6-oxo-tingenol, showed antimicrobial properties on in vitro assays. All extracts and triterpenes, except 3β,11α-di-hydroxylup-20(29)-ene, presented toxicity demonstrated by the larvicidal effect test using Artemia salina.

Tropical biodiversity: has it been a potential source of secondary metabolites useful for medicinal chemistry?

The use of natural products has definitely been the most successful strategy in the discovery of novel medicines. Secondary metabolites from terrestrial and marine organisms have found considerable use in the treatment of numerous diseases and have been considered lead molecules both in their natural form and as templates for medicinal chemistry. This paper seeks to show the great value of secondary metabolites and emphasize the rich chemical diversity of Brazilian biodiversity. This natural chemical library remains understudied, but can be a useful source of new secondary metabolites with potential application as templates for drug discovery.

Chemical characterization by GC-MS and phytotoxic potential of non-polar and polar fractions of seeds of Dioteryx odorata (Aubl.) Willd. from Venezuelan regions

Dipteryx odorata (Aubl.) Willd. is a tall arboreal species native to Central and Northern South America. This paper describes the chemical characterization and phytotoxic potential of polar and non-polar extracts from D. odorata seeds. Structural determinations were accomplished by chemical derivatization and analyzed by GC/MS. The chemical composition of the non-polar fraction (hexane and dichloromethane) presented fatty acids as major constituent. Medium polar and polar fractions (ethyl acetate and ethanol: water) contained carboxylic acid and high 6,7-Dyhidroxycoumarin-β-D-glucopyranoside content, not previously reported for seeds of D. odorata. Extracts showed a significant level of phytotoxic activity, correlated to the content of coumarin derivatives, predominantly in the polar fraction.