| In recent years, the industry of developed rapidly. Planting area expands unceasingly. Comprehensive development and utilization of penoy are important projects. In this study, peony was raw material, using ultra-high pressure-assisted extraction to acquire flavonoids, using aqueous two-phase system to refine and purify, and finally exploring its antioxidant activity and stability. The main results of this thesis are as follow:1. Using ultra-high pressure-assisted method to extract flavonoids from peony flowers. The optimum conditions were:extraction pressure350 Mpa,70% ethanol concentration, solid-liquid ratio 1:40, dwell time 9 min. The order of the factors that affected the peony flavonoids content as follows:extraction pressure>ethanol concentration>solid-liquid ratio>dwell time. Under these conditions, the extraction rate of peony flavonoids was (1.399±0.040)%.2. Using aqueous two-phase extraction and liquid-liquid extraction method for the separation and purification of flavonoids. For aqueous two-phase extraction, choicing ammonium sulfate as split phase salt, the volume ratio of ethanol to water was 1:1, flavonoids were extracted three times, and finally removed impurities by ethanol precipitation. In the result, flavonoids extraction was 94.09%, the extract purity was 47.21%; For the liquid-liquid extraction, choicing n-butanol as the extraction agent, the flavonoids concentration of the bottom phase was 15 mg/ml, two phase ratio was 1.5:1 and extracting times was three. In the result,flavonoids extraction was 96.21%, the extract purity was 29.94%;Through comparing different purification method, aqueous two-phase systems could be precisely controlled the polarity of the organic phase by changing ethanol concentration in order to achieve maximum separation of flavonoids and impurities, therefore the extraction rate and purity of flavonoids is relative high; Macroporous resin method to obtain the purity of flavonoids higher than the extraction method. However, due to the long elution time, temperature, light and other external conditions are difficult to control, resulting in some loss of poor stability flavonoids and relatively low yield of flavonoids.3. Through LC-MS technique, we can determine the seven kinds of flavonoids from peony, namely kaempferol glycosides (hexose+hexose), luteolin glycosides (hexose+pentose), luteolin apple acid glucoside, apigenin glycosides (hexose+ pentose), luteolin monoglycoside (hexose), kaempferol monoglycoside (hexose), apigenin monoglycoside (hexose). Ultra-high pressure influenced flavonoids components content and structure. At 250-350 Mpa condition, two glycoside content decreased, but monoglycoside content continues to rise. This may be ascribed to that two glycoside structure was unstable at this pressure condition, easy to lose carbohydrate chain to form monoterpene glycosides.Ultra-high pressure affect peony antioxidant activity of flavonoids.With the enhanced extraction pressure and the extension of time, the ability of lipid peroxidation inhibition, the DPPH free radical scavenging activities, the hydroxyl radical scavenging ability, the superoxide anion free radical scavenging activities of peony flavonoids all showed an increasing trend. It has a certain relationship with the increase of total flavonoids and partially changing in the structure of flavonoids component.4. Thermal degradation of Peony flower anthocyanin showed one class order kinetics, which displaied thermal degradation rate constant increasing with temperature and light. Greater light intensity would lead to weaker sensitivity to temperature changes of peony flower anthocyanin thermal degradation reaction. Strong stability of complexes formed with stabilizer (or auxiliary toner) by ionic interactions, van der Waals, and hydrophobic interactions, which could prevent nucleophilic group attacks to fade. The present work showed that malonate and Mn2+could be used as a stabilizer to improve the stability of anthocyanins, and anthocyanins have better stability under low pH conditions (pH=2,3). The response value was defined as anthocyanins retention rate and three factors and three levels of response surface analysis experiments were conducted based on the single factor experiment. The results showed that the effect of anthocyanins factors on the stability were malonic acid concentration> pH> Mn2+ concentration. Malonate concentration 88 mmol/L; Mn2+ concentration 6.2 mmol/L; pH 2.6 were optimal conditions, under which anthocyanin retention rate reached 79.21% and the stability increased nearly three-fold in comparasion with the control group. |
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