Saponins from the Compositae Plants: Structures of the Saponins from Aster scaber Thunb
Many triterpene saponins have been isolated from plants belonging to a variety of families such as Leguminosae, Campanulaceae, Cucurbitaceae, and Araliaceae. Compositae, one of the largest families of the flowering plants, comprises more than 13,000 species, which make up more than 10% of all such plants. Nevertheless, very few plants of this family have been investigated as far as saponins are concerned.
KeywordsMethyl Ester Anomeric Proton Triterpene Saponin Methyl Glycoside Anomeric Proton Signal
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References and Notes
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- 3.The sugar species were determined by GC of the methanolysis product after trimethylsilylation. The absolute configurations of the component sugars were determined according to the method reported by Hara et al. 8 Thus, L-cysteine methyl ester and the hydrolysate of scaberoside Hcl methyl ester were heated in pyridine at 60° C for 1 hr, and the resulting mixture of methyl 2-(polyhydroxyalkyl)thiazolidine-4(R)-carboxylates was analyzed by GLC after trimethylsilylation. The absolute configuration of glucuronic acid was determined as D in the same way after conversion of scaberoside Hcl methyl ester to the corresponding glucoside by NaBH4 reduction of the carbomethoxyl group of the methyl glucuronopyranosyl group.Google Scholar
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- 6.Identification of the methylated sugars were performed using the method established by Prof. K.Mihashi, Faculty of Pharmaceutical Sciences, Fukuoka University (unpublished), using standard samples prepared by his group. All standard samples were prepared according to the authorized method and identity was established by checking 1HNMR and 13C NMR spectra, and comparison of the physical data with those reported. The GC retention times and CI-MS spectra of the standard samples were measured in advance. Those of the samples were measured in the same conditions and compared with those of the standard samples. GC: glass column (3 mm i.d. x 1 m) packed with 2% OV17 on Uniport HP (80–100 mesh, GC-MS grade), carrier gas, He (20 ml/min); oven t emperature, 130–190° C (elevation rate 3° C/min). CI-MS: reactant gas, isobutane (1.0–1.5 x 10-5 Torr. in the ion source), ion source temperature, 270° C, ionization voltage, 150 eV, scan range, m/z 100400, scan interval, 4 sec.(instrument. Shimadzu Auto GC-MS 6020 equipped with GC-MS PAC 500 data analyzer).Google Scholar