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Preparation and Antioxidative Activity of Flavonoids from Corn Silk (Zea mays L.)

Author: LiuJun
Tutor: LiuJingBo
School: Jilin University
Course: Of Food Science
Keywords: Corn Flavonoids Antioxidant Isolation and Purification
CLC: R285
Type: Master's thesis
Year: 2011
Downloads: 235
Quote: 1
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Abstract

Corn silk (dried cut stigmata of maize female flowers, Zea mays L.ssp. mays, Poaceae) is a famous traditional herb drug in China. It has many pharmacological activities and other biological activities which were very good for human health. While the flavonoids in corn silk are considered to be responsible for its broad therapeutic effects. In this study, fully-developed, mature Maydis stigma of zea mays L was used as plant material. The detection method of flavonoids in corn silk was established firstly. Then both the conventional extraction methods and supercritical fluid extraction method were employed to prepare flavonoids from corn silk. The advantages and disadvantages of these extraction methods were studied. Box–Behnken design combined with response surface methodology (RSM) was employed to study the effects of three independent variables (temperature, pressure and co-solvent amount) on the extraction yield of the flavonoids and to develop a model equation that could predict and determine the optimum conditions for the highest flavonoid yield.The prepared extract of corn silk was resuspended in warm water and then partitioned sequentially with petroleum ether (bp, 40-60°C), acetic ether, n-butanol and water. Four in-vitro antioxidant models (total antioxidant activity, DPPH radical scavenging activity, reducing power and iron-chelating capacity) were employed in this study to evaluate the antioxidant activities of all the extracted fractions from corn silk. From the results, N-butanol fraction (BF) demonstrated the highest total phenolic content and total flavonoids content accompanied with the highest antioxidant activity compared to other fractions through all antioxidant assays, with EC50 values of 45.95±4.78μg/mL, 65.93±5.38μg/mL, 23.12±2.66μg/mL, 78.16±4.07μg/mL, respectively. The results obtained in this investigation reveal that the total antioxidant activity may be attributed to the presence of phenolics and flavonoids constituents in all the fractionsBF was subjected to open column chromatography on normal phase silica gel, macroporous resin, ODS and Sephadex LH-20, with different organic solvent as mobile phase. TLC analysis was performed on silica gel. The structure of the isolated compounds was identified through the interpretation of the spectra and the comparation of spectral data (UV, and NMR) with reported values. Two flavone glycosides showing potent antioxidant activity were isolated from BF and both the two isolated flavone glycosides, particularly isoorientin-2?′-O-α-L-rhamnoside, demonstrated significant total antioxidant activity, even greater than those of the reference antioxidants. The antioxidant activity assessment of the two flavone glycosides, by using the four in-vitro antioxidant models, showed that they were potent antioxidant compounds.The two isolated flavone glycosides prepared in this study were used as reference and HPLC method was established and optimized to qualitate and quantitate the flavonoids the flavonoids in corn silk. The present investigation may provided the evidence for the utilization of corn silk as a kind of herb drugs and the possibility of using corn silk as source of low-cost natural antioxidant.

Preparation and Antioxidative Activity of Flavonoids from Corn Silk (Zea mays L.)

Abstract

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