Uma nova substância, denominada habenariosídeo {[(2R)-2-[(2,3,4,6-tetra-O-acetil-b-Dglicopiranosil)oxi]-2-(2-metilpropil)-1,4-dioxo-1,4-butanodiil]bis(oximetileno-4,1-fenileno) bis-b-D-glicopiranosídeo}, foi isolada das frações polares do extrato etanólico de Habenaria petalodes Lindl. (Orchidaceae), juntamente com duas substâncias conhecidas e estruturalmente relacionadas, a loroglossina e a militarina. Os flavonóides: isoquercitrina, isorramnetina 3-O-b-D-glicopiranosídeo e isorramnetina 3,7-di-O-b-D-glicopiranosídeo, também foram isolados. As estruturas do habenariosídeo e das demais substâncias foram determinadas pela análise dos dados de EM, IV, UV e RMN mono e bidimensional e comparação com os dados publicados na literatura.
IntroductionThe Brazilian flora is exceedingly rich and comprises more than 56,000 endemic plant species. Among the 22,000 members of the family Orchidaceae that have been described worldwide, approximately 1,800 grow endemically in Brazil. 1 In spite of its size and diversity when compared with other plant families, a relatively small number of orchid species have been investigated regarding their chemical composition, with about 300 secondary metabolites reported so far. These included, among others, flavonoids, terpenoids, quinones, phenanthrenes, stilbenes, lignans, and glucosylated benzyl esters of succinic, malic, tartaric and citric acids. [2][3][4][5][6] The phytochemical investigations of Brazilian Orchidaceae are also restricted to few published works: a report concerning the presence of methylated C-glycosylflavones as taxonomic markers in fifteen orchids, 7 and the investigation of the floral composition of other twenty-one species. 8 The genus Habenaria (Orchidaceae) comprises over 600 species of which around 170 occur in Brazil. 9 However, to the best of our knowledge only Habenaria repens Nutt. was chemically investigated so far, resulting in the identification of habenariol, a compound with potent feeding deterrent activity. [10][11][12] In the present paper we report the first phytochemical investigation of Habenaria petalodes Lindl., describing the isolation and structure elucidation of six compounds (1-6), including a new 2-malic acid derivative (4) denominated habenarioside. Cota et al. 1099 Vol. 19, No. 6, 2008
Results and DiscussionThe whole plant was extracted by maceration with ethanol and the extract was subjected to liquid-liquid partition between CH 2 Cl 2 and MeOH:H 2 O (1:1) to afford an organic and a hydroalcoholic fraction. The latter was subjected to solid phase extraction (SFE) using RP-18 cartridges followed by semi-preparative RP-HPLC to yield six compounds (Figure 1-2).The ESI-MS of compounds 1 and 5 exhibited quasimolecular ion peaks ([M + Na] + ) at m/z 765 and m/z 749, respectively. Their molecular weight, together with their UV, 1 H and 13 C NMR data were in accordance with those reported for loroglossin (1) and militarin (5). 5,14 Habenarioside (4) which was given the trivial name habenarioside as it is a mono-glucosylated derivative of hab...