大叶钩藤总生物碱提取溶剂的研究及钩藤碱的纯度测定

目的:筛选大叶钩藤总生物碱工业化提取的适宜溶剂,分离纯化得到钩藤碱并测定其纯度。方法:用不同的溶剂提取大叶钩藤的总生物碱,柱层析分离得到钩藤碱晶体,用HPLC测定晶体的纯度。结论:溶剂的选择直接影响总生物碱的提取量,氯仿是大叶钩藤总生物碱工业化提取的适宜溶剂,用通过柱层析可以得到纯度高达为95.49%的钩藤碱晶体。     

大叶千斤拔黄酮类成分提取及抗氧化活性研究

通过单因素试验及响应面试验优化大叶千斤拔总黄酮的乙醇回流提取工艺条件,并对提取物的抗氧化活性进行评价。结果表明：优化后的提取工艺条件为提取时间52 min,料液比（m_{大叶千斤拔}∶V_乙醇）1∶6 （g/mL）,乙醇体积分数70%,提取温度60 ℃,该条件下提取物的总黄酮含量为75.47 μg/mg;提取物对ABTS⁺自由基、DPPH自由基清除能力的IC₅₀分别为0.044 9,0.212 3 mg/mL,总抗氧化能力及对Cu²⁺和Fe³⁺还原能力的IC₅₀分别为0.389 6,0.221 9,0.731 7 mg/mL。说明建立的最佳提取工艺可有效获取大叶千斤拔总黄酮成分;大叶千斤拔黄酮类物质具有较强的体外抗氧化活性。     

Purification and properties of polyphenol oxidase from oil bean (Pentaclethra macrophylla Benth) seeds

Polyphenol oxidase extracted from oil bean (Pentaclethra macrophylla) seeds was purified 165-fold over the crude enzyme extract. The apparent molecular weight of the enzyme by gel filtration was 110.8 k ± 9.0 k while SDS-PAGE indicated a single species of molecular weight 28.0 k. A copper content of 1.9 mg g^?1 corresponds to one copper atom for each of the four subunits. The purified enzyme oxidised pyrogallol, catechol, 4-methylcatechol and L-dihydroxyphenylalanine but had low activity towards tyrosine. p-Cresol, caffeic acid and cholorogenic acid were not oxidised. Thio-compounds were strong inhibitors of the enzyme. The phenolic compounds tyrosine, resorcinol and orcinol inhibited catechol oxidation but became oxidised in the process.     

水苎麻叶挥发性成分分析及其抗菌活性研究

采用GC-MS分析方法对水苎麻叶中的挥发性成分进行分析。从中鉴定出20个组分,其中油酸含量最高,占44.47%。抗菌活性实验结果显示,挥发性成分对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、酿酒酵母菌具有抑制和杀灭作用。     

Forage quality and tannin concentration and composition of a collection of the tropical shrub legume Flemingia macrophylla

A collection of 23 Flemingia macrophylla (Willd.) Merrill accessions of different growth habits and contrasting digestibility and one Flemingia stricta reference accession were assessed for forage quality with particular emphasis on digestibility, condensed tannin concentration and fiber content. Large differences in in vitro dry matter digestibility (IVDMD) (356 to 598 g kg^?1), content of crude protein (CP) (121 to 254 g kg^?1) and extractable condensed tannins (CT) (0 to 268 g kg^?1), protein‐binding capacity of extractable CT or astringency (1.7 to 7.9 protein‐binding entities) (PBE) and monomer composition of extractable CT were detected. IVDMD and extractable CT were negatively correlated and extractable CT was positively correlated with protein‐binding capacity. Prodelphinidin was positively and propelargonidin negatively correlated with protein‐binding capacity of extractable CT. The accessions CIAT 18438, CIAT 21083, CIAT 21090 and CIAT 22082 were superior to the most widely used accession CIAT 17403 in terms of forage quality and could be an option in production systems with acid infertile soils. In future evaluations, particular attention needs to be paid to chemical and structural features related to the composition of extractable CT and their effect on nitrogen utilization by ruminants. Copyright © 2006 Society of Chemical Industry     

Investigation into Pentaclethra macrophylla seed oil: Identification of hexacosanoic (C26:0) and octacosanoic (C28:0) fatty acids

The fatty acid composition of seed oil from Pentaclethra macrophylla was analysed by gas-liquid chromatography and mass spectrometry. Linoleic acid (56.6%) was the major fatty acid with oleic (16.1%) and lignoceric (10.5%) acids making a significant contribution. Two long-chain fatty acids not commonly found in vegetable oils were identified. These were shown to be hexacosanoic (C26:0) and octacosanoic (C28:0) acids; 4.8% and 1.0% of each acid being present, respectively. The oil content of the seeds was 42.0%.     

Biochemical changes during the natural fermentation of the african oil bean (Pentaclethra macrophylla) for the production of Ugba

Changes in the activities of major enzymes and in the proportion of the principal chemical components during the nataral fermentation of ugba from African oil bean (Pentaclethra macrophylla Bentham) were studied. The activities of the enzymes were related to changes in chemical composition. α-Amylase, proteolytic and lipolytic enzyme activity remained detectable throughout the 72-h fermentation period, and reached a maximum at 24-36 h. The levels of amino nitrogen, ammonia nitrogen, reducing sugar, titratable acidity and pH increased with time. A seven-fold increase in the amino nitrogen level occurred during the fermentation. The temperature of the fermentation and the moisture level reached maximum values at 24 h and 48 h of fermentation respectively. These results could provide useful indices for the improved evaluation of ugba fermentation.     

The ruminal degradability of fibre explains part of the low nutritional value and reduced methanogenesis in highly tanniniferous tropical legumes

BACKGROUND: Limited forage quality and low methanogenesis from fermentation of tropical shrub legumes is often attributed to high contents of condensed tannins (CTs), but characteristics of the fibre may be important, too. Using the rumen‐simulation technique an attempt was made to separate the influence of tannins and fibre on ruminal digestion and methanogenesis. Legumes with CTs (Calliandra calothyrsus, Flemingia macrophylla) and plants free of CTs (Vigna unguiculata, Brachiaria humidicola) were used. To separate effects, either CTs were inactivated using polyethylene glycol or purified fibres free of CTs were obtained. In experiment 1, legumes replaced one third of grass in the diet and urea was supplemented. In experiment 2, only purified fibres and casein were incubated. RESULTS: Purified fibres had a different degradability (low in legumes with CTs). Lignin prevented mainly hemicellulose from being degraded while the extent of degradation of hemicellulose seemed to have determined methanogenesis. In the mixed diets these effects were small when the supply of N was sufficient. When CTs were inactivated, fibre degradation was still lower with Calliandra than with Vigna. CONCLUSION: Properties of fibre, especially lignification, of CT‐rich plants help to explain the low feeding value of such forages, but CTs represent the over‐riding factor. Copyright © 2008 Society of Chemical Industry