Do extrato hexânico de Eleocharis sellowiana foram isolados o novo triterpeno 3α-hidroxi-13α,17α,21β-hopano-15,19-diona e hexadecanoato de E-fitila, caracterizados por dados de RMN e EM.A new triterpene named 3α-hydroxy-13α,17α,21β-hopan-15,19-dione and E-phytyl hexadecanoate were isolated from the hexanic extract of Eleocharis sellowiana. NMR and MS experiments determined the molecular structures.
Keywords: Eleocharis, Cyperaceae, hopane-like triterpene
IntroductionThe genus Eleocharis R. Br. (Cyperaceae, Cyperoideae, Scirpeae) includes about 200 species, occurring in wet environments like swamps, lakes and rivers margins. Their aerial parts are formed by simple, not ramified stalks that end in a spiciform inflorescence formed by numerous very inconspicuous flowers. Their subterraneous parts are formed by roots and stem (called rhizome or stolon, depending on its form). E. sellowiana Kunth occurs in Mexico, Colombia, Paraguay and Brazil. This species is widely distributed in São Paulo State. 1 As many other plants from wet environments like swamps, lakes and rivers margins, Eleocharis species are subject of only a few studies. According to the literature 2 only E. dulcis Trin., E. coloradoensis (Britt.) Gilly, E. acuta R. Br., E. microcarpa Torr. and E. smallii L. had been subjected to phytochemical analysis before.In continuation of our phytochemical analysis of Eleocharis genus, 3 the hexanic extracts of E. sellowiana (subterraneous and aerial parts) were subjected to a detailed chromatographic analysis resulting in the isolation of a new pentacyclic triterpene named 3α-hydroxy-13α,17α,21β-hopan-15,19-dione (1) and E-phytyl hexadecanoate (2) (Figure 1). On the other hand, when the hydrogens H-16 were irradiated, only the hydrogen H-17 was observed. The absence of polarization transference between H-17 and H-21 points out to a very small coupling constant between these hydrogens and consequently to a cis-D/E rings fusion with a β-isopropyl group. The C/D rings fusion should be a cis-fusion with the hydrogen H-13 in a α-position. that corroborated with the hydroxyl group at C-3 (m/z 207, 16%, 1a and m/z 189, 100%, 1b) and with carbonyl groups location at D-and E-rings (m/z 318, 85%, 1c; m/z 300, 24%, 1d; m/z 303, 20%, 1e; m/z 277, 32%, 1f) (Figure 4). Compound 2 (C 28 H 48 O), isolated from the hexanic extract of E. sellowiana (aerial part), was identified as Ephytyl hexadecanoate by comparison of their 1 H and 13 C NMR and MS data with those previously published. 7 The occurrence of compound 2 in the genus Eleocharis is described here for the first time.
Results and Discussion
Experimental
GeneralThin layer chromatography (TLC): Silica gel 60 F 254 Al sheets (Merck); detection at 254 and 365 nm and with anisaldehyde in acidic ethanol solution, 8 CC = column chromatography. 1 H, 13 C NMR and 2D experiments Varian Inova-500 (Palo Alto, CA, USA) spectrometer at 11 tesla. Chemical shifts of the compounds were recorded in CDCl 3 solutions and were quoted relative to TMS for 1 H NMR (δ 0.0) and to CDCl 3 (δ 77.0)...
