Development of simultaneous methods for diosgenin and phytosterols analysis in yam
Date Issued
2005
Date
2005
Author(s)
Yu, Chia-wen
DOI
zh-TW
Abstract
Dioscorea (or Chinese yam) is a common raw material for drug and health food manufacture. Similar but separated analytical assays were generally conducted to determine contents of two groups of biological active compounds, phytosterols and diosgenin. One gas-liquid and one high performance of liquid chromatographic methods were established to simultaneously determine these two groups of compounds both belonging to steroids. The methods included acidic and alkali hydrolysis, solvent extraction and chromatographic analysis. A DB-5 (poly(phenylmethyl) siloxane, 5% phenyl) capillary column was selected for gas-liquid chromatography. The retention time of diosgenin peak was among those of phytosterols. A C18 column was selected for liquid chromatography and gradient of acetonitrile-methanol mixed solvent was used as eluant. The diosgenin with high polarity was eluted out at higher acetonitrile ratio 95:5 (v/v) and the phytosterols were eluted out at lower ratio 65:35 (v/v). The major phytosterols found in yam were beta-sitosterol, stigmasterol and campesterol. Two detection systems, ultraviolet absorption at 205nm (UV205) and evaporative light scattering detection (ELSD), were used and compared for detection sensitivity and stability. The UV205 had higher sensitivity with detection limits in the range of 0.03~0.09 ug which was ten-times higher than ELSD, but ELSD tolerant higher level of noise and did not have baseline interference caused by solvent gradient. Lipid extraction prior acid hydrolysis was found to be necessary to avoid absorption effects of fibers and acid resistant residues. Trails for extracting efficiency were conducted on Soxhlet extracting apparatus and on soak-and-shake extraction. The results indicated that sequential extraction using hexane and methanol as solvent on Soxhlet apparatus yielded the highest determining values. Hexan-isopropanol (1:2, v/v) mixture also served as an efficient solvent as well as mixture of chloroform-methanol (2:1, v/v). Phytosterol contents were determination on three representative Taiwanese yam cultivars, D. pseudojaponica, D. alata L., Tainun 2, and D. alata L. var. purpurea). Phytosterols were found in all samples and the total phytosterol contents were in the range of 9.9~30.1mg/100g. Diosgenin was only found in D. pseudojaponica samples included tubers, leaves, vines and the content of edible tuber portion was 15.2 mg/100g.
Subjects
山藥
薯蕷皂配基
植物固醇
氣相層析法
液相層析法
yam
diosgenin
phytosterol
GC
HPLC
Type
thesis
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