A Labdane diterpene from the aerial parts of Egletes viscosa less

Abstract

Um novo labdano glicosilado, 8α-hidroxilabd-14(15)-eno-13(S)-O-β-D-ribopiranosídeo, foi isolado das partes aéreas de Egletes viscosa Less, juntamente com o 13-epi-esclareol, barbatol, tarapacol, espinasterol, ternatina e triacontano. As estruturas dos compostos isolados foram elucidadas pelo uso de métodos espectrométricos e preparação de derivados químicos.A new labdane glycoside, 8α-hydroxylabd-14(15)-ene-13(S)-O-β-D-ribopyranoside, was isolated from the aerial parts of Egletes viscosa Less, along with 13-epi-sclareol, barbatol, tarapacol, spinasterol, ternatin and triacontane. The structures of the isolated compounds were elucidated by the use of spectrometric methods and preparation of chemical derivatives. Keywords: Asteraceae, Egletes viscosa, diterpene glycoside, 8α-hydroxylabd-14(15)-ene-13(S)-O-β-D-ribopyranoside IntroductionEgletes viscosa Less (Asteraceae) is an annual herb mostly native to intertropical Americas. It is known in the Northeast of Brazil as "macela" or "macela-da-terra" and grows throughout the margins of river and lakes as soon as the raining season ends. The flower buds are largely sold in the herbal stores and used in the folk medicine as emmenagogue, diaphoretic, 1 stomachic and antidiarrhoeal. 2 Previous studies with E. viscosa have reported the isolation of biologically active flavonoids and diterpenoids. [3][4][5][6][7][8][9][10][11][12][13][14] Recently, Lee et al reported the isolation of labdane diterpene glycosides and flavonoids from the entire plant native from Peru. 15 In continuation of the work with this species, we report now the isolation of the new labdane glycoside 8α-hydroxylabd-14(15)-ene-13(S)-O-β-D-ribopyranoside 1 in addition to 13-epi-sclareol, 16 barbatol, 17 tarapacol, 18 spinasterol, 19 ternatin, 7, 20-23 and triacontane from the aerial parts of E. viscosa. The complete proton and carbon assignments of the known compounds and of the new diterpene 1, including the unpublished 13 C and 1 H NMR data of the new derivatives 2-4 were accomplished by the use of a series of 2D NMR experiments such as 1 H-1 H COSY, HMQC and HMBC. Results and DiscussionCompound 1 was isolated as a white solid. Its molecular formula was determined as C 25 H 44 O 6 from the NMR and EImass spectroscopy measurements (m/z = 440). The absorption band in the IR spectrum at 3400 cm -1 was consistent with hydroxyl groups. Inspection of the 1 H NMR spectrum indicated the presence of three angular methyl groups at δ 0.81 (s, H-19 and H-20) and 0.88 (s, H-18), two methyls attached to oxygenated tertiary carbons at δ 1.11 (s, H-17) and 1.35 (s, H-16), and an anomeric hydrogen at δ 4.32 (d, J 6.4 Hz,. Moreover, the presence of a vinyl moiety was suggested by the signals at δ 5.92 (dd, J 17.8, 10.9, H-14); 5.22 (dd, J 17.8, 1.2, H-15a) and 5.17 (dd, J 10.9, 1.2, H-15b). The 13 C NMR spectral data of 1 confirmed 1375 Silva-Filho et al. Vol. 18, No. 7, 2007 the β-ribopyranosyl unit by the signals at δ 98.6 (C-1´), 73.1 (C-3´), 71.3 (C-2´), 68.2 (C-4´) and 65.1 (C-5´); 24 together with 20 carbon ...

The association between drugs and herbal products: In vitro enhancement of the antibiotic activity by extracts of dry floral buttons of Egletes viscosa L. (macela)

“…The level of flavonoids was particularly high. Studies of E. viscosa have reported the isolation of biologically active flavonoids and diterpenoids and of new labdane glycosides, which display the most diverse biological activities [15].…”

Diterpenoids

“…28 A nor-labdane arabinoside has been obtained 29 from Conyza blinii, a plant used in Chinese folk medicine, whilst other labdane glycosides have been isolated from Aster reitchianus 30 and from the bitter fern, Gleichenia quadripartita. 31 Labdanes have been reported as constituents of Orthosiphon labiatus, 32 Egletes viscosa, 33 and Aquilegia hybrida. 34 16-Hydroxycommunic acid has been shown 35 to be a cytotoxic constituent of Podocarpus fasciculus.…”