Fatty acids and terpenoids from Trigonia fasciculata

Abstract

A fração lipídica do extrato hexânico das raízes de Trigonia fasciculata foi analisada por CG/EM sob a forma de seus ésteres metílicos, identificando-se dezessete ácidos graxos, sendo o ácido oléico (38,8%) o principal componente. A análise por CG/EM da fração menos polar da parte insaponificável do extrato hexânico das raízes permitiu identificar quinze sesquiterpenos não oxigenados, sendo o α-santaleno (28,4%) o componente majoritário. Cromatografia em gel de sílica da fração mais polar permitiu o isolamento de dois triterpenos conhecidos, ácido betulínico e friedelina, e o diterpeno inédito 7-(2-hidroxiacetil)-10-hidroxitetradecaidro-1-metileno-4b,7,10a-trimetilfenantreno (6α-hidroxi-15-oxo-allodevadarool). Todas as substâncias isoladas e identificadas são inéditas para a espécie. A determinação estrutural foi realizada por derivatização química, comparação com dados da literatura, análise espectral, incluíndo RMN 2D (COSY, HETCOR e COLOC), e cristalografia de raios X.The fatty portion of the hexane extract from roots of Trigonia fasciculata has been determined by GC/MS analysis of the methyl ester mixture. Seventeen fatty acids were identified and oleic acid (38.8%) was the major component. The GC/MS analysis of the less polar fraction of the nonsaponifiable part of the root hexane extract allowed the identification of fifteen sesquiterpenes and α-santalene (28.4%) was the major component. Chromatography over silica gel of the more polar fraction allowed the isolation of two known compounds: betulinic acid and friedelin, and a novel diterpene 7-(2-hydroxy-acetyl)-10-hydroxy-tetradecahydro-1-methylene-4b,7,10a-trimethylphenantrene (6α-hydroxy-15-oxo-allodevadarool), all unknown for the species. Structure determination was accomplished by chemical derivatization, comparison to literature data and spectral analysis, including 2D NMR (COSY, HETCOR, COLOC) and X-ray crystallography. Keywords Results and DiscussionTFRH, the clear viscous brownish extract obtained after hexane extraction of ground roots of T. fasciculata, yielded a precipitate after standing at room temperature. Silica gel chromatography column of the precipitate allowed the isolation of friedelin and betulinic acid. Coarse chromatography of the mother liquor yielded a non-polar fraction after elution with hexane designated TFRH(1). Hydrolysis with KOH/EtOH 1:1 solution, yielded the free fatty acids mixture (TFRH(1)/FA) and a unsaponifiable 407 Fatty Acids and Terpenoids from Trigonia fasciculata Vol. 14, No. 3, 2003 portion (TFRH(1)/NS) after usual work up. Methylation of an aliquot of TFRH(1)/FA with BF 3 /MeOH 14% solution followed by GC/MS analysis of the methyl ester mixture allowed the identification of the fatty acids listed in the Experimental Section. Silica gel chromatography of TFRH(1)/NS yielded a yellowish fraction by elution with hexane. 1 H and 13 C NMR analysis indicated its terpenoid character. GC/MS analysis of this fraction, followed by comparison of the mass spectra obtained for each compound with a computer library data ban...

Dolabranes from the Chinese Mangrove, Ceriops tagal

“…Dolabrane diterpenoids are a small group of natural products reported mainly from plants. To date, only 37 dolabranes have been characterized from the plant genera Araucaria , Croton , Dichapetalum , Endospermum , Erythroxylum , Fagonia , Givotia , Helichrysum , Mallotus , Petalostigma , Rondeletia, Trigonia , and Thujopsis ,− ,− and from the liverwort Schistochila aligera , whereas 18 dolabranes have been identified from the mangrove, Ceriops tagal . Obviously, C. tagal is a valuable source for the production of dolabranes.…”