Saponinas triterpênicas de Tocoyena brasiliensis Mart. (Rubiaceae)

The present communication reports the isolation and identification of four triterpenoid saponins from the chloroform extract of the leaves of Tocoyena brasiliensis: 3-O-β-D-quinovopyranosyl quinovic acid, 3-O-β-D- quinovopyranosyl cincholic acid, 3-O-β-D-glucopyranosyl quinovic acid and the 28-O-β-D-glucopyranosyl ester derivative of quinovic acid as binary mixtures, respectively. From the ethanol extract a flavonoid identified as ramnazin-3-O-rutinoside was obtained. The structures of these compounds were assigned by data analysis of ID and 2D NMR spectrometry and comparison with data recorded in the literature for these compounds.

Characterization of flavonoid and naphthopyranone derivatives from Eriocaulon ligulatum using liquid chromatography tandem mass spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI-MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (1H-13C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple-Bond Correlation (HMBC), 1H-15N HMBC, 1H- 1H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p-Cl and p-Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p-NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.