Characterization of the fraction components using 1D TOCSY and 1D ROESY experiments. Four new spirostane saponins from Agave brittoniana Trel. spp. Brachypus

Abstract

A careful NMR analysis, especially 1D TOCSY and 1D ROESY, of two refined saponin fractions allowed us to determine the structures of four new saponins from a polar extract of the Agave brittoniana Trel. spp. Brachypus leaves. A full assignment of the 1H and 13C spectral data for these new saponins, agabrittonosides A-D (1-4), and one previously known saponin, karatavioside A (5) is reported. Their structures were established using a combination of 1D and 2D (1H, 1H-COSY, TOCSY, ROESY, g-HSQC, g-HMBC and g-HSQC-TOCSY) NMR techniques and ESI-MS. Moreover, the work represents a new approach to structural elucidation of saponins in refined fractions by NMR investigations.

Characterization of three saponins from a fraction using 1D DOSY as a solvent signal suppression tool. Agabrittonosides E–F. Furostane Saponins from Agave brittoniana Trel. spp. Brachypus

“…This is the same as the sequence observed in Agabrittonoside A. [1] The anomeric proton signal of the sixth sugar, glucose, H-1 glc (δ 4.80) showed long-range correlations to H-26 (δ 3.59 and 3.92) and C-26 (δ 75.2).…”

“…These peaks are consistent with an empirical molecular formula of C 61 H 100 O 33 , which was supported by comparative analysis of the 13 C NMR and 13 C DEPT spectroscopic data. The NMR spectrum of compound 1 (Tables 1 and 2) was similar to that previously described for the saponin from A. brittoniana, [1] Agabrittonoside A, with modifications in the spirostane cycle.…”

“…(ssp. Brachypus), [1] we report here the structural elucidation of a fraction obtained after repeated chromatography processes.…”

Saponins of Agave: Chemistry and bioactivity

“…), 2.14 to 2.29 (H-1eq. ), 3.92 to 4.06 (H-2), 43.4 to 45.7 (C-1), 69.7 to 72.7 (C-2) and 83.4 to 84.8 (C-3) (Jain, 1987;Macias et al, 2007Macias et al, , 2010Perez et al, 2013;Perez et al, 2014;Uniyal et al, 1991b;. Three spirostanol glycosides with 2b-OH have been reported from Agave utahensis.…”

“…The 1 H and 13 C chemical shifts of this double bond are completely unaffected by hydroxyl substitutions in ring A (Macias et al, 2007;Perez et al, 2013), 12-oxo group (Perez et al, 2013(Perez et al, , 2014, glycosylation at C-10 (Abdel- Gawad et al, 1999) or even the type of sapogenin skeleton (i.e. furostan or spirostan) (Abdel-Gawad et al, 1999;Macias et al, 2010;Perez et al, 2014;Zou et al, 2006).…”