【作者】 宋艳；

【导师】 汪云；

【作者基本信息】 江南大学 ， 分析化学， 2008， 硕士

【摘要】 黑玉米是玉米的一个新品种,其籽粒角质层不同程度地沉淀黑色素,外观乌黑发亮。黑玉米不仅色泽独特,而且营养丰富,富含水溶性黑色素、多种氨基酸和各种人体必需的微量元素。本课题以黑玉米为研究对象,对黑玉米中黑色素的提取工艺、组成、抗氧化性及营养成分氨基酸进行了研究。研究内容主要包括以下三个部分:1.黑玉米中黑色素的提取工艺及组成研究;2.黑玉米和黄玉米提取物的抗氧化性研究;3.毛细管电泳-电化学法检测黑玉米皮中三种氨基酸的含量。黑玉米色素属天然花青苷色素。通过正交实验确定了黑色素的最佳提取条件:95%的乙醇溶液、料液比1:30、pH=1、提取时间45 min;并采用液质联用(LC-MS)技术对山东和山西两种黑玉米中花青苷的种类进行了确定,其中山东黑玉米中主要含有两种花青苷,分别是矢车菊和天竺葵花青素;山西黑玉米中主要含有三种花青苷,分别是矢车菊、天竺葵和芍药花青素。为了研究其抗氧化活性和比较抗氧化效果,本实验以常见的黄玉米与黑玉米为原材料,进行了一系列抗氧化性能实验。用不同极性的溶剂对玉米中的抗氧化性物质进行超声提取,并对所得提取物进行清除DPPH·自由基实验,得出黄玉米和黑玉米各自的不同溶剂提取物中抗氧化性最强的部分;以两种玉米提取物中抗氧化性最强的部分为材料,进行邻苯三酚自氧化抑制实验和抑制猪油自氧化实验,并对两种玉米提取物中抗氧化性最强的部分进行总黄酮含量的测定。结果表明:黄玉米和黑玉米各自的不同溶剂提取物中抗氧化性最强的部分均为80%乙醇提取物;黄玉米乙醇提取物中总黄酮含量为16.2mg/8g,黑玉米乙醇提取物中总黄酮含量为51.5mg/8g,三种抗氧化实验均说明黑玉米抗氧化性比黄玉米好,具有较好的清除自由基和抗氧化的能力。采用OPA为柱前衍生化试剂,用毛细管电泳-电化学检测(CE-ED)的方法测定了黑玉米中亮氨酸、缬氨酸和丙氨酸的含量。以直径为300μm的碳圆盘电极为工作电极,研究了运行缓冲液pH值、检测电压、分离电压和进样时间对三种氨基酸分离和检测的影响,得到了最佳电泳条件:100mmol/L硼砂(pH7.8)为运行缓冲液、检测电压0.95V(vs.SCE)、分离电压18kV、进样时间6s。在优化条件下,三组分可在18 min内完全分离,检出限分别为2.5×10-4 g/L、2.5×10-4 g/L、5.0×10-4 g/L。该方法准确、简单易行,样品处理简单,为氨基酸分离测定提供了一种快速灵敏的检测方法。更多还原

【Abstract】 Black corn is a new corn species, which color is different from other corn, mainly because there is a plenty of black pigment in its epidermis. It is rich in water-soluble black pigment , a variety of essential amino acids and various trace elements. Taking black corn as experimental material, studied the extraction and composition of black corn pigment, evaluated antioxidative activities of corn by a series of antioxidative tests and determined the contents of amino acids in black corn epidermis. The thesis mainly includes the following three parts :1. study on extraction technology and composition of black corn pigment. 2. study on the antioxidative activities of extracts from black corn and yellow corn. 3. determination of three amino acids in black corn epidermis by capillary electrophoresis with electrochemical detection (CE-ED).Firstly, black corn pigment is a natural anthocyanin pigment. The effects of different factors on extraction of pigment with orthogonal test were investigated. The optimal parameters of extraction of black corn pigment were as fellows: ethanol–water (95:5, v/v) as extracting solvent, solid-liquid ratio 1:30, extracting time 45 min. Liquid chromatography-mass spectrometry (LC-MS) were applied to determine the components of black corn pigments. The results showed that there were two major anthocyanins in ShanDong sample: cyanidin and pelargonin, and three major anthocyanins in ShanXi sample: cyanidin, pelargonin, and paeonidin.Secondly, to compare the antioxidative activity with other common corn, we chose yellow corn and black corn as the raw materials to carry on a series of antioxidative tests. The different fractions of corn antioxidative extracts were obtained using solvents with different polarities. The antioxidative activity of these extracts were assessed for 1,1-Diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging activity to find the strongest antioxidative fractions in both corns. Taking the strongest antioxidative fractions as experimental objects, their antioxidiative activities were investigated by two different methods in scavenging superoxide anion (O2-) generated by pyrogallol autoxidant system and restrainning lard oxidation. The total flavonoids contents of ethanolic extract from the both corns were determined. The results showed that ethanol-water antioxidative extract fraction had the strongest antioxidative capacities among the five fractions in both corns .The total flavonoids contents of ethanolic extract were 16.2 mg/8g and 51.5 mg/8g for yellow corn and black corn, respectively. Three antioxidative experiments shown that the antioxidative activity of black corn was better than that of yellow corn.Finally, using o-phthaldehyde (OPA) as a pre-column derivative agent, the contents of leucine, valine and alanine in black corn epidermis were determined by CD-ED in this paper. A 300μm diameter carbon disk electrode was used as the working electrode, the effects of several factors such as pH of running buffer, separation voltage, injection time, and detection potential were investigated to acquire the optimum conditions. The optimum CE-ED conditions were as fellows: applied potential to the working electrode at 0.95V (vs.SCE), 100 mmol/L borate solution (pH 7.8) as running buffer, injection time 6s, the analytes could be well separated within 18 min at a separation voltage of 18 kV in a 100 mmol/L borax running buffer . The detection limits (S/N=3) were 2.5×10-4 g/L、2.5×10-4 g/L、5.0×10-4 g/L, for leucine, valine and alanine, respectively. This method is accurate and feasible, the sample preparation is simple, which provided a fast and sensitive determination method for amino acids.更多还原