16,17-Seco- and 2,3:16,17-di-Seco-pregnanes from Guarea guidonia

Abstract

Dois novos seco-e di-seco-pregnanos, 2α,3β-diidróxi-2β,19-hemicetal-16,17-seco-pregn-17-en-16-oato de metila (1) e ácido 2,3:16,17-di-seco-pregn-17-en-3-óico-16-oato de metila-19-hidróxi-2-carboxílico-2,19-lactona (2), foram isolados da casca do caule de Guarea guidonia. Suas estruturas foram determinadas com base em dados espectrais, particularmente RMN uni-e bidimensionais e massas. Os esqueletos pregnânicos incomuns seco-e di-seco destes compostos estão sendo relatados pela primeira vez em Meliaceae, assim como a ocorrência de pregnanos no gênero Guarea.Two new seco-and di-seco-pregnanes, 2α,3β-dihydroxy-16,17-seco-pregn-17-ene-16-oic acid methyl ester 2β,19-hemiketal (1) and 2,3:16,17-di-seco-pregn-17-ene-3-oic acid-16-oic acid methyl ester-19-hydroxy-2-carboxylic acid-2,19-lactone (2), have been obtained from the trunk bark of Guarea guidonia. Their structures have been established by a combination of 1D-and 2D-NMR spectroscopic techniques and MS data. The unique seco-and di-seco-pregnane carbocyclic skeletal types as found in compounds 1 and 2 are being reported in the Meliaceae for the first time as well as the occurrence of pregnanes in the genus Guarea.Keywords: Guarea guidonia, Meliaceae, seco-pregnane, di-seco-pregnane IntroductionSpecies of Guarea (Meliaceae) are found throughout tropical America and also in Africa. 1 This genus has been the subject of a number of investigations and is known as a rich source of secondary metabolites, including limonoids, sesqui-, di-and triterpenes and steroids.2-5 Guarea guidonia L. Sleumer is a tree widely distributed in Brazil and the wood bark of this plant is employed in traditional medicine as an abortive and febrifugal agent and the seeds are used to treat rheumatism while the leaves and fruits are reported to be toxic to cattle. 6,7 Moreover, seed extracts of G. guidonia were shown to have anti-inflammatory activity in rats while antiviral properties against pseudo-rabies virus were reported for crude extracts of leaves and fruits. 7,8 In previous works sesquiterpenes were isolated from the stem bark of a specimen of G. guidonia occurring in south-eastern Brazil 3 while a specimen of G. guidonia collected in the central-western region of Brazil afforded a number of constituents, including di-, tri-and sesquiterpenes and steroids from the leaves 4 and compounds of the sesquiterpene, limonoid and coumarin types from the trunk bark. 5 In the course of the investigation of the trunk bark of the latter specimen, 5 the CHCl 3 -soluble fraction of the ethanol extract was shown to contain two minor steroidal derivatives which, nevertheless, were not further isolated. The present study of the trunk bark of this same specimen has now allowed the isolation of these constituents which were characterized as two novel seco-and di-seco-pregnane derivatives (1 and 2). Their structural elucidation was mainly based on 1D and 2D NMR spectroscopic techniques. Results and DiscussionCompound 1 was obtained as an oil. Its molecular formula was established as C 22 H 34 O 5 by NMR s...

Flavonoids and a neolignan glucoside from Guarea macrophylla (Meliaceae)

“…1 H and 13 C 1D and 2D NMR were recorded at 500 MHz ( 1 H) and 125 MHz ( 13 C) on a Varian ® spectro meter using TMS as the internal standard with DMSO-d 6 and CD 3 OD as solvents. The high resolution ESI mass spectra were obtained from a Bruker Apex III 70e Fourier transform ion cyclotron resonance mass spectrometer (Bruker Daltonics, Billerica, USA).…”

“…3 Furthermore, some biological activities, particularly antiprotozoal, have been demonstrated experimentally. 4,5 Several phytochemical studies on the genus Guarea have been published and a wide variety of secondary metabolites including coumarins, 4 sesquiterpenes, 6 diterpenes, 4,7 and triterpenes have been identified. 8 Guarea macrophylla is a tall tree found in the south and southeast of Brazil and in the Amazon region.…”

Sesquiterpenos de sementes de Guarea guidonia (Meliaceae)

“…Na medicina popular é utilizada no tratamento de reumatismo, hidropsia e tumores artríticos, tendo, ainda, propriedades adstringentes, purgativas, febrífugas, abortivas, eméticas e anti-inflamatórias. 1 Estudos fitoquímicos prévios dos extratos hexânico e etanólico da casca do tronco desta espécie, além do óleo volátil de suas folhas, resultaram no isolamento de limonoides, 2-3 esteroides, 4 seco-esteroides, 5 cumarinas, 2 di-, 4,6,7 tri-4 e sesquiterpenos. 2,4,8 O presente trabalho trata do estudo fitoquímico de sementes de um espécime de G. guidonia, que levou ao isolamento de sete sesquiterpenos, sendo dois deles inéditos: 6α-etoxieudesm-4(15)-eno-1β-ol (1), eudesm-4(15)-eno-1β,6α-diol (2), 5-epi-eudesm-4(15)-eno-1β,6β-diol (3), eudesm-4(15)-eno-1β,5α-diol (4), eudesm-4(15),7-dien-1β-ol (5), (7R*)-oposit-4(15)-eno-1β,7-diol (6) e (7R*)-5-epioposit-4(15)-eno-1β,7-diol (7) (Figura 1).…”