虎杖根中黄酮类化合物对脂氧合酶活性抑制

从虎杖根中提取黄酮类化合物,并研究了提取出的虎杖根黄酮类化合物对大豆和毛尖茶叶中脂氧合酶活性的抑制作用,并与人工合成抗氧化剂BHA和BHT的抑制作用进行比较,结果表明:虎杖根中黄酮类化合物提取率为16. 92%。虎杖根黄酮类化合物对大豆(毛尖茶叶)脂氧合酶活性抑制:IC50=12. 53(9. 17) mg/m L; BHA:IC50=1. 89(1. 98) mg/m L; BHT:IC50=1. 77(1. 76) mg/m L,虎杖根黄酮类化合物对大豆脂氧合酶和毛尖茶叶中的脂氧合酶活性都有一定的抑制作用。     

紫外分光光度法研究不同摊放时间毛尖茶叶脂氧合酶活性的变化

采用紫外分光光度法,以亚油酸钠为反应底物,研究都匀团山、高寨地区不同部位毛尖茶叶在摊放不同的时间时,毛尖茶叶中脂氧合酶酶活性的变化。结果表明:团山毛尖茶叶随着摊放时间的延长,LOX活性都是慢慢降低,而高寨地区的则是先上升后降低,在摊放到第三天时LOX活性有一个最大值。高寨和团山地区毛尖茶成叶的LOX活性比嫩叶高,高寨地区毛尖茶叶LOX活性总体都比团山地区的高。     

脂氧合酶的研究进展

脂氧合酶是植物代谢途径的关键酶,该酶在植物体中主要作用于亚油酸和亚麻酸,生成的产物对植物的生长发育有很重要的作用,文章对脂氧合酶的结构,可能催化机理,脂氧合酶活性的测定以及活性的抑制进行了讨论,并对脂氧合酶模型化合物的研究进展进行了综述。     

查尔酮化合物抗炎活性与作用机制的研究进展

查尔酮化合物具有抗炎作用并有多种作用机制。介绍查尔酮化合物具有代表性的抗炎作用机制：抑制NF-κB通路、激活Keap1-Nrf2-ARE通路、抑制环氧合酶和5-脂氧合酶活性以及抑制醛糖还原酶活性，为新型有效抗炎药的开发提供新思路。     

甜茶叶中黄酮类化合物提取条件研究

用正交实验方法考察了甜茶叶中黄酮类化合物的最佳提取条件。研究结果表明 ,在80℃条件下 ,用 6倍于叶重的 70 %乙醇加热提取 3次 ,每次 50min ,甜茶叶中黄酮类化合物提取的效果最好。     

甜茶叶中黄酮类化合物提取条件研究

用正交实验方法考察了甜茶叶中黄酮类化合物的最佳提取条件。研究结果表明，在80℃条件下，用6倍于叶重的70％乙醇加热提取3次，每次50min，甜茶叶中黄酮类化合物提取的效果最好。     

植物脂氧合酶的研究进展

植物代谢的关键酶是脂氧合酶(LOX),该酶直接或间接参与植物的生长、发育、成熟和衰老的调控过程。对脂氧合酶的酶学特性、脂氧合酶与防虫及抗病害的关系、植物脂氧合酶活性的抑制、脂氧合酶对果实、粮食的储藏及食品质量的影响等方面进行了介绍,并对脂氧合酶在果实成熟过程中作用,对储存、产品质量的影响等方面的研究进展及现状进行展望。     

黄酮类化合物抗肝细胞癌HepG2细胞系的研究进展

大量研究表明,在肿瘤治疗中,从中药中提取的黄酮类化合物具有抗肿瘤活性,或与化疗药物联合使用可提高化疗效率。作者综述了黄酮类化合物诱导的抑制Hep G2细胞系的细胞内信号通路,介绍了黄酮类化合物抗HBV/HCV活性的研究现状,并对黄酮类化合物在癌症治疗中的应用进行了展望。     

红薯叶黄酮类化合物的提取及其抗氧化活性的测定

采用不同方法提取红薯叶中的黄酮类化合物,通过比较提取率及黄酮类化合物的含量,确定用体积分数为60%的乙醇提取为最佳的提取方法,同时采用烘箱贮存法测定了红薯叶黄酮类化合物在猪油中的抗氧化活性.结果表明,红薯叶黄酮类化合物具有明显的抗氧化效果,且抗氧化活性随用量的增加而增强,抗氧化效果好于抗坏血酸和柠檬酸.     

红薯叶茎中黄酮的提取工艺研究

通过液相萃取法提取红薯叶茎中黄酮类化合物。比较了红薯叶茎中的黄酮类化合物含量,考察了不同提取剂、提取时间等因素对红薯叶中黄酮类化合物提取率的影响。实验结果表明:红薯叶中的黄酮类化合物的含量高于茎中的黄酮类化合物含量,60%乙醇-水溶液提取效率最好为。较佳工艺条件为:红薯叶25 g,以60%乙醇-水溶液提取4 h,可提取黄酮类化合物约32 mg以上。     

Effects of rosemary extracts and major constituents on lipid oxidation and soybean lipoxygenase activity

Rosemary (Rosemarinus officinalis L.) leaves were extracted with three different solvents, namely hexane, acetone and methanol. A reverse-phase high-performance liquid chromatography system in combination with a mass detector was used to quantitate the content of carnosol, carnosic acid and ursolic acid in the rosemary extracts. All rosemary extracts showed strong inhibitory effects on lipid oxidation and soybean lipoxygenase activity.     

Caulerpenyne and Related Bis‐enol Esters Are Novel‐Type Inhibitors of Human 5‐Lipoxygenase

Caulerpenyne (CYN) is a sesquiterpene from green algae with known inhibitory properties against soybean lipoxygenase. Here we introduce a detailed structure–activity study elucidating the inhibitory effects of CYN and a library of six synthetic CYN analogues on isolated human 5‐lipoxygenase (5‐LO) and cellular 5‐LO in polymorphonuclear leukocytes. Essential structural elements are identified and a structurally simplified inhibitor is introduced. The modes of 5‐LO inhibition by CYN and the synthetic inhibitors cannot be assigned to any of the known categories of lipoxygenase inhibitors. These compounds clearly interfere directly with 5‐LO and represent rather small and flexible molecules, with unique structures among 5‐LO inhibitors identified thus far.     

从竹叶中同步提取多糖、茶多酚和黄酮的研究

研究高压脉冲电场法同步提取竹叶中黄酮、茶多酚和多糖的工艺。以竹叶为原料,在电场强度、脉冲数、提取介质pH和料液比4个单因素实验的基础上,采用L9(34)正交实验确定最优化工艺。结果表明,采用高压脉冲电场法进行同步提取,竹叶黄酮、茶多酚和多糖提取率分别可达到2.48%,0.93%和3.54%,竹叶黄酮与多糖的提取率比传统方法提高了25%以上,但茶多酚的提取率略有降低。该工艺可同步有效地从竹叶中提取黄酮、茶多酚和多糖,对于综合开发竹叶活性成分具有指导意义。     

不同加工方式茶叶的抗过敏活性

对几种云南大叶茶及同种茶叶加工的红茶和绿茶水提取液进行透明质酸酶体外抑制实验和肥大细胞组胺抑制实验 ,评价它们的抗过敏活性。结果表明 :不同加工方式的同种茶叶 ,抗过敏活性存在差异 ,红茶抗过敏作用较绿茶强。同时测定其茶叶多酚含量 ,初步试验表明 ,茶叶中存在除儿茶素外的其它抗过敏有效成分     

Highly simplified preparation of tea flavonoids from surplus tea leaves by the novel three-phase extraction and purification

A novel three-phase extraction and purification procedure was developed to prepare high-quality flavonoids from surplus tea leaves. Flavonoids were selectively extracted in ethyl acetate (EtOAc) by the EtOAc-water-leaf three-phase extraction, with 91.2% extraction efficiency, more than 50% higher than the traditional water extraction. The EtOAc extracts were purified by the EtOAc-water- montmorillonite/charcoal three-phase adsorptive purification at 98% recovery. Highly purified flavonoids were obtained with less than 1.0% caffeine. The overall flavonoid recovery reached 90.3%, more than 40% higher than traditional methods. This procedure highly simplified the processes and significantly increased the recovery of flavonoid production from tea leaves.     

Potential role of lipoxygenases in defense against insect herbivory

The potential role of the plant enzyme lipoxygenase in host resistance against the corn earwormHelicoverpa zea was examined. Lipoxygenase is present in most of the common host plants ofH. zea, with highest activity in the leguminous hosts such as soybean and redbean. Treatment of dietary proteins with linoleic acid and lipoxygenase significantly reduced the nutritive quality of soybean protein and soy foliar protein. Larval growth was reduced from 24 to 63% depending upon treatment. Feeding byH. zea on soybean plants caused damage-induced increases in foliar lipoxygenase and lipid peroxidation products. Larvae feeding on previously wounded plant tissue demonstrated decreased growth rates compared to larvae feeding on unwounded tissue. Midgut epithelium from larvae feeding on wounded tissues showed evidence of oxidative damage as indicated by significant increases in lipid peroxidation products and losses in free primary amines. The potential role of oxidative and nutritional stress as a plant defensive response to herbivory is discussed.     

Chemical composition and lipoxygenase activity in soybeans as affected by genotype and environment

Environmental and genetic influences on the chemical composition and lipoxygenase activity of 24 soybean genotypes (groups IV-S and V) were determined. The soybeans were grown at two climatically different locations within the state of Georgia. Oil and protein contents and fatty acid composition of the oil in soybeans were affected by the environment. Five genotypes from group IV-S has a fatty acid composition of the oil different from the other genotypes in the group. These differences appeared to be genetically controlled. The level of lipoxygenase activity in soybeans also appeared to be genetically controlled and not influenced by the environment. The study indicated that soybean genotypes could be selected for a specific climatic region based on oil fatty acid composition and lipoxygenase activity.     

Bioactive compounds, antioxidant, xanthine oxidase inhibitory, tyrosinase inhibitory and anti-inflammatory activities of selected agro-industrial by-products

Evaluation of abundantly available agro-industrial by-products for their bioactive compounds and biological activities is beneficial in particular for the food and pharmaceutical industries. In this study, rapeseed meal, cottonseed meal and soybean meal were investigated for the presence of bioactive compounds and antioxidant, anti-inflammatory, xanthine oxidase and tyrosinase inhibitory activities. Methanolic extracts of rapeseed meal showed significantly (P < 0.01) higher phenolics and flavonoids contents; and significantly (P < 0.01) higher DPPH and nitric oxide free radical scavenging activities when compared to that of cottonseed meal and soybean meal extracts. Ferric thiocyanate and thiobarbituric acid tests results showed rapeseed meal with the highest antioxidant activity (P < 0.01) followed by BHT, cotton seed meal and soybean meal. Rapeseed meal extract in xanthine oxidase and tyrosinase inhibitory assays showed the lowest IC(50) values followed by cottonseed and soybean meals. Anti-inflammatory assay using IFN-γ/LPS stimulated RAW 264.7 cells indicated rapeseed meal is a potent source of anti-inflammatory agent. Correlation analysis showed that phenolics and flavonoids were highly correlated to both antioxidant and anti-inflammatory activities. Rapeseed meal was found to be promising as a natural source of bioactive compounds with high antioxidant, anti-inflammatory, xanthine oxidase and tyrosinase inhibitory activities in contrast to cotton and soybean meals.     

Relative inhibitory potencies of flavonoids on 12-lipoxygenase of fish gill

The relative efficacy of 10 flavonoid compounds and some common antioxidants in inhibiting 12-lipoxygenase of fish gill was determined. Lipoxygenase activity was measured by oxygen consumption with polarography and formation of hydroxy fatty acid using thin layer chromatography with autoradiography. Generally, the inhibition of 12-lipoxygenase by flavonoids was noncompetitive. The lipoxygenase product pattern did not change in the presence of flavonoids. Fisetin (3,3′,4′,7-tetrahydroxyflavone) and quercetin (3,3′,4′,5,7-pentahydroxyflavone) were the most potent inhibitors of 12-lipoxygenase, with IC₅₀'s of 0.25 and 0.4 μM respectively. These were compared with IC₅₀'s values of 5, 1000 μM for BHA (t-butylhydroxyanisole) and BHT (t-butylhydroxytoluene) respectively. Possible inhibitory mechanisms and relationships between flavonoid structure and inhibitory potencies are discussed.     

Two soybean genotypes lacking lipoxygenase-1

The U.S. Department of Agriculture soybean germplasm collection (6,499 accessions) was screened for genotypes with greatly reduced or missing lipoxygenase-1 (L-1) [linoleate: O₂ oxidoreductase, EC 1.13.11.12] and lipoxygenase-2 and L-3 (L-2 and L-3) activity. The L-1 assay used linoleic acid dispersed in Tween-20 at pH 9.0 as the substrate (acid assay) and the L-2 and L-3 assay used linoleic acid methyl ester dispersed in ethanol at pH 7.0 as the substrate (ester assay). The spectrophotometric assay based on conjugated diene formation at 234 mm was used in the qualitative screening procedure. Two plant introductions (PI), 133226 from Indonesia and PI 408251 from Korea lacked L-1 activity. Oxygen uptake, electrophoresis and isoelectric focusing confirm the lack of detectable L-1 activity in the seed of these two genotypes. Radial diffusion against soybean seed lipoxygenase antiserum showed that the two genotypes are missing a precipitin band that normal soybean genotypes and purified lipoxygenase from soybean seed exhibit. Neither the L-1 variants nor any other accessions tested had greatly reduced activity with the ester assay. An erratum to this article is available at .