Components of Ether-Insoluble Resin Glycoside (Convolvulin) from Seeds of Quamoclit pennata

Abstract

The so-called resin glycosides are well known as purgative ingredients, which are characteristic of some crude drugs such as Mexican Scammony Root, Orizaba Root, Jalapae Tuber, Pharbitidis Semen, and Rhizoma Jalapae Braziliensis. These drugs all originate from Convolvulaceae plants and can be roughly divided into an ether-soluble resin glycoside called jalapin and an ether-insoluble resin glycoside called convolvulin.1) In a previous paper, 2) we reported the isolation and structural elucidation of a new glycosidic acid called quamoclinic acid A that was obtained along with three organic acids, 2S-methylbutyric, n-decanoic, and n-dodecanoic acids, upon alkaline hydrolysis of the jalapin fraction of the seeds of Quamoclit pennata BOJER. Further, we isolated four genuine jalapins, quamoclins I, II, III, and IV, from the fraction.2) This paper deals with the component organic and glycosidic acids of the convolvulin fraction of the seeds of this plant.The alkaline hydrolysis products of the convolvulin fraction previously obtained 2) were fractionated into organic acid and glycosidic acid fractions. Gas chromatography (GC) of the former revealed the presence of isobutyric, 2-methylbutyric, and tiglic acids. Further, the organic acid fraction was methylated with diazomethane-ether and then examined using GC; it exhibited four peaks assignable to methyl tiglate, methyl nilate, methyl 7-hydroxydecanoate, and methyl 7-hydroxydodecanoate.The organic acid fraction was acylated with p-bromophenacyl bromide followed by chromatographic separation to give p-bromophenacyl 2-methylbutyrate (1), p-bromophenacyl tiglate (2), p-bromophenacyl nilate (3), p-bromophenacyl 7-hydroxydecanoate (4), and p-bromophenacyl 7-hydroxydodecanoate (5) (Fig. 1). The absolute configuration of 1 was defined as S by comparison of the specific rotation with an authentic sample, 3) and that of 3 was considered to be 2R,3R by comparisons of the specific rotation and the 1 H-NMR spectrum of 3 with those of an authentic sample. 3)However, the absolute value of the specific rotation of 3 was approximately 6-fold greater than that of p-bromophenacyl nilate (3Ј) previously obtained in a similar process as that used for 3 from the convolvulin fraction of Pharbitidis Semen.3) Thus the optical purities of 3 and 3Ј were examined using their 1 H-NMR spectra of (Ϫ)-a-methoxy-a-trifluoromethylphenylacetic acid (MTPA) esters 4) (3a from 3; 3Јa from 3Ј), and it was confirmed that 3 did not contain its enantiomer, while 3Ј was a mixture of p-bromphenacyl esters of the 2R,3R-and the 2S,3S-nilic acid in the ratio of approximately 6 : 5 on the basis of the ratio of intensities of signals due to H 3 -5 of the (2R,3R)-form and that of the (2S,3S)-form.The alkaline hydrolysis of 4 and of 5, with subsequent diazomethane-ether treatment, gave methyl 7-hydroxydecanoate (4a) and methyl 7-hydroxydodecanoate (5a), respectively. The configurations at C-7 of 4a and 5a were determined using Mosher's method. 4) Compounds 4a and 5a were converted into the corresponding (Ϫ)-MTPA ester...

Identification and Characterization of Component Organic and Glycosidic Acids of Crude Resin Glycoside Fraction from Calystegia soldanella

“…1). 4) The absolute configurations of 1 and 3 were defined as S and 2S,3S, respectively, by comparison of the specific rotations and 1 H-NMR spectral data for (ϩ)-a-methoxy-a-trifluoromethylphenylacetic acid (MTPA) ester (3a) of 3 with those of authentic samples (Fig. 1).…”

“…1). 4) Acidic hydrolysis of the glycosidic acid fraction gave aglycone and monosaccharide fractions. Methylation of the former with trimethylsilyldiazomethane-hexane yielded methyl 11S-jalapinolate (4), which was identified by 13 C-NMR spectral data of 4 and 1 H-NMR spectral data of (ϩ)-MTPA ester (4a) of 4 ( Fig.…”

“…was dissolved in 1 M KOH (10 ml) and heated at 95°C for 1 h. After cooling, the reaction mixture was adjusted to pH 4 with 1 M HCl and shaken with ether (30 mlϫ4). The ether layer was dried over MgSO 4 and evaporated in vacuo to give an oil (organic acid fr., 63 mg). The H 2 O layer was chromatographed over MCI gel CHP20 (solvent, H 2 O→acetone).…”

“…in 1 M HCl (2 ml) was heated at 95°C for 1 h. The reaction mixture was diluted with H 2 O (5 ml) and then extracted with ether (5 mlϫ6). The ether extract was dried over MgSO 4 and concentrated in vacuo to give a residue (15 mg). Treatment of the residue with trimethylsilyldiazomethane-hexane, followed by evaporation, gave a powder, which was chromatographed over a silica gel column [solvent, hexane-EtOAc (10 : 1→ 5 : 1→2 : 1→1 : 1)] to afford methyl jalapinoate (4, 5 mg The aqueous layer was neutralized with Amberlite MB-3 (Organo Co., Tokyo) and then evaporated in vacuo to give a monosaccharide fr.…”

Five New Resin Glycoside Derivatives Isolated from the Convolvulin Fraction of Seeds of <i>Quamoclit pennata</i> after Treatment with Indium(III) Chloride in Methanol

“…10,11) On the other hand, we reported the structures of seven glycosidic acids, quamoclinic acids B, C, D, E, F, G, and H along with isobutyric, 2S-methylbutyric, 2R-methyl-3R-hydroxybutyric (2R,3R-nilic), (E)-2-methylbut-2-enoic (tiglic), 7S-hydroxydecanoic, and 7S-hydroxydodecanoic acids upon alkaline hydrolysis of the crude convolvulin fraction of the seeds. 12,13) However, despite numerous attempts, isolation of pure resin glycosides from the crude convolvulin fraction 11) of the seeds of Q. pennata has been unsuccessful, until now. Previous results suggested that resin glycosides in the crude convolvulin fraction possessed at least one carboxyl group.…”