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Mechanism of Outfields Enhancing Extraction Flavonoids from Ginkgo Biloba and the Effect of Separation Methods on Antioxidant Activtity

Author: OuYangNaNa
Tutor: LiXiangZhou
School: Central South University of Forestry Science and Technology
Course: Forest Chemical Process Engineering
Keywords: Ginkgo biloba flavonoids Microwave-assisted extraction Ultrasonic-assisted extraction Outfields enhancing mechanism Antioxidant
CLC: S792.95
Type: Master's thesis
Year: 2008
Downloads: 65
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Abstract


Series researches of Ginkgo biloba leaves which have important bioactive compounds by new technologies of outfields enhancing extraction were studied in this dissertation. The technology condition of microwave-assisted and ultrasonic-assisted extraction of flavonoids from Ginkgo biloba leaves were optimized by orthogonal experiment. From microcosmic and dynamic points, during the whole extraction changes of microcosmic, dynamic characteristics and outfields enhancement mass-transfer mechanism were all studied and analyzed by optical microscope and scanning electron microscope respectively. The variation of antioxidant activity about extraction of Ginkgo biloba (EGB) by different extracting techniques in separation methods such as solvent extraction, macroporous resin purification were systematical-ly investigated. The main research contents and results are as follows:1. Ginkgo biloba flavonoids were extracted from Ginkgo biloba leaves by solvent reflux extraction (SRE), microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) through orthogonal experiment. The optimum extraction conditions were as follows respectively:by SRE ethanol volume fraction as 80%, ratio of material to liquid as 1:40, reflux temperature as 80℃,extraxtion time as 180 min; by MAE ethanol volume fraction as 80%, ratio of material to liquid as 1:25, extraxtion temperature as 70℃,extraxtion time as 15 min; by UAE ethanol volume fraction as 80%, ratio of material to liquid as 1:20, extraxtion temperature as 50℃,extraxtion time as 40 min; the flavonoids yield by these three methods were 3.10%,4.09%,3.68% respectively.2. Optical microscope and scanning electron microscope (SEM) were employed to study cell-rupure and enhancing mass-transfer mechanism of SRE, MAE and UAE were discussed. The results showed that different extraction ways and time had different effect on cell organization. Microwave and ultrasonic fields made cellwall rupure more easier and lowered the mass-transfer resistance. With extraction time prolonged, the disruption of celluar structures were more obvious, so the effective ingredients could be dissolved and permeated into solvent easily.3. Dynamic characteristics of Ginkgo biloba flavonoids under different outfields extraction were studied concerning heating temperature, solution concentration and solid/liquid ratio.The figures of yield to time and ln[(C∞/C∞-C] to time implied that MAE extracting could reach its equilibtium quickly and be stable at the intial stage, the extraction process corresponded to first-rate dynamic equation characteristics. So higher temperature and solvent concentration would increase yield than lower ones at the first period of extraction.However, the flavonoids yield increased slowly under UAE which could be explained that the influence of temperature to process was lower than MAE owing to cavitation effect, the extraction process corresponded with first-rate dynamic equation characteristics. Better extraction effect could be obtained under lower temperature, the ratio of solid to liquid and high solution concentration.4.The influence of separation technology of solvent extraction and resin adsorption on the antioxidant activity of EGB by MAE and UAE were researched.The results showed that samples of resin adsorption and UAE had better antioxidant ability than solvent extraction and MAE.In solvent extraction technology, for scavenging DPPH free radicals, the aqueous portion extracted by ethyl acetate had the strongest activity, the IC50 value were 1.44μg/mL by MAE and 1.23μg/mL by UAE respectively; for scavenging OH free radicals, the aqueous portion extracted by ethyl acetate had the strongest activity, the IC50 value were 5.42μg/mL by MAE and 5.47μg/mL by UAE respectively; for scavenging O2- free radicals, the aqueous portion extracted by petroleum ether had the strongest activity, the IC50 value were 1.08μg/mL by MAE and 1.10μg/mL by UAE respectively.In resin adsorption technology, for scavenging DPPH free radicals, ethanol concentration was 30% as eluate had the strongest scavenging activity, the IC50 value were 1.65μg/mL by MAE and 1.47μg/mL by UAE respectively; for scavenging OH free radicals, ethanol concentration was 80% as eluate had the strongest scavenging activity, the IC50 value were 1.05μg/mL by MAE and 1.25μg/mL by UAE respectively; for scavenging O2- free radicals, ethanol concentration 10%,30%,50% as eluate had better effect on scavenging O2- free radicals.

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CLC: > Agricultural Sciences > Forestry > Forest tree species > Broad-leaved trees > Ginkgo
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