Minor sesquiterpenes from the volatile oil from leaves of Guarea guidonia Sleumer (Meliaceae).

The essential oil from leaves of Guarea guidonia was subjected to chromatographic separation procedures to afford nine sesquiterpenes; two of them are new eudesmane derivatives. The chemical structures of the obtained compounds were characterised by spectrometric analysis, mainly mass spectrometry and NMR.

Aplicação de técnicas cromatográficas e espectrométricas como ferramentas de auxílio na identificação de componentes de óleos voláteis / Use of chromatographic and spectrometric techniques to help the identification of volatile compounds

A metodologia usual aplicada para análise de óleos voláteis, tais como CG, CG-EM, índice de Kovats e, em alguns casos, sistemas computacionais especialistas, não permitem a identificação de compostos desconhecidos os quais devem ser isolados para que tenham suas estruturas moleculares elucidadas. Essa limitação é ainda maior quando tais óleos apresentam potencial biológico uma vez que existe grande dificuldade no isolamento das substâncias ativas, as quais devem ser obtidas em seu estado puro para avaliação da atividade. Assim, este trabalho descreve uma metodologia de separação não usual (cromatografia rápida em sílica e sílica impregnada com AgNO3) associada a técnicas espectrométricas (EM, RMN de ¹H e RMN de 13C) as quais permitiram a purificação e caracterização de compostos de óleos voláteis contendo estruturas ainda não conhecidas e/ou biologicamente ativas.

The usual techniques applied for analyzing the chemical constitution of volatile oils, such as GC, GC-MS, Kovats Index and, in some cases, specialist computational systems, do not allow the identification of the unknown or biologically active compounds which must be isolated in order to have their molecular structures elucidated. This problem is higher if the oils present biological potential, which will induce in the isolation of active substances, once these substances must be obtained in their pure state to activity evaluation. Thus, this paper describes an unusual chromatographic separation (flash chromatography on SiO2 and SiO2/AgNO3) associated to spectrometric techniques (MS, ¹H NMR and 13C NMR), which lead to the purification and structural elucidation of the unpublished and/or biologically active constituents from volatile oils.

Synthesis and preliminary biological evaluation of beta-carotene and retinoic acid oxidation products.

Synthesis of the beta-carotene oxidation product, 2,3-dihydro-5,8-endoperoxy-beta-apo-carotene-13-one (1) was achieved in six steps starting from beta-ionone. Photo-oxygenation of all trans-retinoic acid (8) and 13-cis-retinoic acid (9) produced a mixture of 5S*,8S*-epidioxy-5,8-dihydroretinoic acid (10) and 13-cis-5S*,8S*-epidioxy-5,8-dihydroretinoic acid (11). Methylation of the crude photo-oxygenation mixture afforded the corresponding methyl esters 12 and 13, respectively, both of which underwent ready aerial oxidation yielding hitherto unknown oxidation products of retinoic acid identified as methyl 5S*,8S*-epidioxy-9,10beta-epoxy-5,8,9,10-tetrahydroretinoate (14) and methyl 13-cis-5S*,8S*-epidioxy-9,10beta-epoxy-5,8,9,10-tetrahydroretinoate (15). Evaluation of 1, all trans-retinoic acid (8), 13-cis-retinoic acid (9), and the photo-oxygenation products 10-15 in a panel of five cancer cell lines showed 1 to be inactive and that 11 is significantly cytotoxic compared with the other retinoic acid analogs suggesting the requirement of the carboxylic acid moiety and the cis-geometry of the 13(14) double bond for cytotoxic activity.

Terpenoids from Guarea guidonia.

The volatile oil and the methanol extract from the leaves of Guarea guidonia, Meliaceae, were individually submitted to chromatographic separation. A sesquiterpene (2S*)-eudesma-5,7-dien-2-ol, together with six known ones, were isolated from the volatile oil. The methanolic extract afforded two known and two new triterpenes (23S*)-cycloart-24-ene-3 beta,23-diol and (23R*)-cycloart-24-ene-3 beta,23-diol, besides three known sesquiterpenes, one known diterpene and two steroids. Their structures were established on the basis of spectrocopic data, mainly by 1H and 13C NMR spectroscopic analyses.