Estudo fitoquímico de Vellozia graminifolia (Velloziaceae)

Abstract

Vellozia graminifolia (Velloziaceae) was collected at the Chapada da Diamantina, State of Minas Gerais, and identified by Professora Nanuza Luiza de Menezes of the Instituto de Botânica da Universidade de São Paulo (IB-USP). The investigation of the hexane extract of the roots, stems and pods led to the isolation of a mixture of aliphatic alkanes, a mixture of pentacyclic triterpenes (lupenone, aamirone, b-amirone and lupeol), monoisoprenylated flavonoids 3,5-dihydroxy-3',4'- dimethoxy-6,7:2,1-[2-(1-metyletenyl)furo] flavone, 5-hydroxy-3,3',4'-trymethoxy- 6,7:2,1-[2-(1-metyletenyl)furo] flavone and of the diterpene 3b-hydroxylabd-8(17)- en-15-oic acid. The ethyl acetate extract furnished a mixture of the monoisoprenylated flavonoids 4'-hydroxy-3,5,3'-trymethoxy-6,7:2, l-[2-(1-methyl ethenyl)furo] flavone and 3,5,3',4'-tetramethoxy-6,7:2,1-[2-(1-methyl ethenyl)furo] flavone. The structural determination of these natural products was made on the basis of spectral data, including 2D-NMR techniques such as the 1H-Detected Heteronuclear Multiple-Quantum Coherence (HMQC), 1H-Detected Multiple-Bond xxxvi Heteronuclear Multiple-Quantum Coherence (HMBC) and Nuclear Overhauser Effect Spectroscopy (NOESY), together with the aid of chemical analysis. To the best of our knowledge, 3,5-dihydroxy-3',4'-dimethoxy-6,7:2,1-[2-(1- metyletenyl)furo] flavone is hitherto unreported as a natural product. The diterpene of the labdane series was identified for the first time in Velloziaceae family. The use of high resolution gas chromatography coupled to mass spectrometry allowed to observe the presence, in the hexane extract of Vellozia graminifolia, of triterpenes common to the Vellozia genus. The use of HRGC at high temperatures coupled to mass spectrometry proved to be useful as an alternative method for the identification of flavonoids in mixtures.