Effect of the degree of sulfation on the physicochemical and biological properties of Pleurotus eryngii polysaccharides

Polysaccharides extracted from Pleurotus eryngii were chemically modified by sulfation and the effects on the structural and biological properties of the polysaccharides were investigated as a function of the degree of sulfation. ¹³C NMR spectroscopy demonstrated that polysaccharides from P. eryngii were mainly composed of β-(1 → 3)-glucans with β-(1 → 6) branches. The structure of the sulfated polysaccharides was confirmed by FT-IR and their degree of substitution (DS) was determined to be 0.12–0.92. When P. eryngii polysaccharides were sulfated they were shown to be effective in inhibiting cancer cell growth in a dose-dependent way. Furthermore, their DPPH radical quenching effects were improved with increasing degree of sulfation. Thus, it seemed that the chemical modification of P. eryngii polysaccharides by sulfation effectively enhanced their potential biological properties.     

Evaluation of reducing power and radical scavenging activities of water and ethanol extracts from sumac (Rhus coriaria L.)

The purpose of this study was to determine the reducing power, metal chelating, and radical scavenging capabilities of water and ethanol extracts of sumac (Rhus coriaria L.), comparatively. The water and ethanol extracts of sumac were evaluated for their radical scavenging activities by means of the DPPH and DMPD assays. Water extract of sumac (R. coriaria L.) scavenged radicals effectively with EC₅₀ values of 36.4 ??g/ml for DPPH free radical and 44.7 ??g/ml for DMPD cation radical. Similarly, the total reducing power of water extract was found higher than ethanol extract in both potassium ferricyanide reduction (FRAP) and cupric ions reduction capacity methods (CUPRAC). 2,2′-Bipyridine was used to determine the metal chelating activity and the result of water extract was found higher than ethanol extract. Total phenolic and total flavonoid contents of both extracts were studied as well. The values of water extract were found to be higher than that of ethanol extract. The present study found that water extracts of sumac (R. coriaria L.) have effective antioxidant and radical scavenging activities as compared to ethanol extracts.     

New nitrogen-containing bromophenols from the marine red alga Rhodomela confervoides and their radical scavenging activity

In addition to nine known bromophenol derivatives, five new nitrogen-containing bromophenols were isolated from an ethyl acetate extract of the marine red alga Rhodomela confervoides. By using spectroscopic methods, the structures of the new compounds were identified as 3-(2,3-dibromo-4,5-dihydroxybenzyl)pyrrolidine-2,5-dione (1), methyl 4-(2,3-dibromo-4,5-dihydroxybenzylamino)-4-oxobutanoate (2), 4-(2,3-dibromo-4,5-dihydroxybenzylamino)-4-oxobutanoic acid (3), 3-bromo-5-hydroxy-4-methoxybenzamide (4), and 2-(3-bromo-5-hydroxy-4-methoxyphenyl)acetamide (5). All of these bromophenols showed potent scavenging activity against DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals, with IC(50) values ranging from 5.22 to 23.60μM. These compounds also displayed moderate activity against ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonate) radicals, with Trolox Equivalent Antioxidant Capacity values (TEAC) ranging from 2.11 to 3.58mM. The results obtained in this study demonstrate that the bromophenols obtained from R. confervoides may have potential application in food and/or pharmaceutical fields as natural antioxidants.     

槲皮素-锌(Ⅱ)配合物清除自由基的活性研究

为改善槲皮素的水溶性,将其制成锌(Ⅱ)配合物,测定了槲皮素-锌(Ⅱ)配合物对四种自由基——DPPH·、·OH自由基、O-2·自由基以及烷基自由基的清除能力,并同VC、BHT进行了比较。并通过体内实验,测定其在小鼠体内的总抗氧化能力。结果表明:在实验质量浓度范围内(0.05～1.2mg/mL),槲皮素-锌(Ⅱ)配合物对DPPH·、·OH自由基、O-2·自由基的清除率可达90.51%、85.65%和79.81%;其对烷基自由基的抑制率为82.67%,且其抗氧化活性强于VC和BHT。小鼠体内的总抗氧化能力的测定结果显示,槲皮素-锌(Ⅱ)配合物在高剂量时具有最大抗氧化力,为12.7980±0.9131单位/mL血清。结果表明,槲皮素-锌(Ⅱ)配合物是一种有效的自由基清除剂。     

枇杷核黄酮类物质微波法提取及对羟自由基清除作用研究

本文对微波法提取枇杷核中黄酮类物质进行了研究，通过单因素及L9（3^4）正交试验，得到最佳工艺条件：m（乙醇溶液）／m（枇杷核）=15，提取功率为296W，时间120s提取3次，50％的乙醇溶液。按此最佳方法总黄酮提取率为1．41％。微波法与传统溶剂提取法比较，具有提取时间短、提取率高等优点。同时研究了该提取物对羟自由基清除作用，黄酮类物质对羟自由基的清除作用呈线性相关，相关系数R^2为0．9865。     

26种市售食醋抗氧化性的比较

测定了不同品种食醋中酚类、黄酮类化合物含量及DPPH自由基清除活性,并分析了总酚、总黄酮含量与DPPH自由基清除活性的相关性。结果显示,不同品种食醋的自由基清除作用和它们含有的酚类及黄酮类成分相关,相关系数分别为0.952 3和0.869 1。总酚含量、总黄酮含量可作为评价食醋抗氧化性的指标,总酚含量、总黄酮含量、DPPH自由基清除率可作为鉴别不同品种食醋的指标。     

Enzymatic Synthesis and Antioxidant Activity of 1‐Caffeoylglycerol Prepared from Alkyl Caffeates and Glycerol

Caffeic acid (CA) as a strong antioxidant has lower solubility in nonpolar media, which limits its application in the food industry. To increase the lipophilicity of CA, 1‐caffeoylglycerol (1‐CG) was synthesized by lipase‐catalyzed transesterification of alkyl caffeates in solvent‐free system and its antioxidant capacity was investigated. Methyl caffeate was screened as the appropriate substrate from tested alkyl caffeates with a yield of 90.63%. Ethyl acetate was used for extracting 1‐CG from enzymatic reactants and could be easily recycled. The produced 1‐CG had 2.5‐ and 10‐fold lower values of half maximal inhibitory concentration (IC₅₀) (10.86 and 3.99 μM) than butylated hydroxyanisole by 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging and β‐carotene‐linoleic acid assays, respectively. Thus, 1‐CG is an excellent antioxidant for application in the functional food industry. Using alkyl caffeates and glycerol as substrates to produce 1‐CG catalyzed by immobilized lipase in a solvent‐free system is a simple, selective, and safe bioprocess that can readily be achieved in the food industry, and the product 1‐CG could be widely applied in food, nutraceutical, and biotechnological products.     

Radical Scavenging Activity of Lipophilized Products from Lipase-Catalyzed Transesterification of Triolein with Cinnamic and Ferulic Acids

Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.     

一些天然提取物对超氧自由基和羟基自由基的清除作用

皮肤衰老与自由基有着密切关系。利用邻苯三酚自氧化产生超氧自由基（Ｏ２）,Ｆｅｎｔｏｎ反应产生羟基自由基（ＯＨ）,以比色法测定了一些天然提取物对这二种自由基的清除作用,结果表明：这些提取物大都具有清除作用,其中以芦丁、槲皮素,黄芪总黄酮较强。     

冬凌草硒多糖的制备、表征及抗氧化活性分析

本研究以济源冬凌草多糖为原料，选用化学合成方法对多糖进行结构修饰。采用UV、FT-IR、SEM、TGA、HPLC等方法对冬凌草多糖以及硒多糖结构特征进行了表征；通过DPPH（1,1-二苯基-2-三硝基苯肼）自由基法、羟自由基法等4种方法对其抗氧化活性进行了探究。结果：制备的硒多糖中硒质量分数为1.35 mg/g。硒化修饰后，冬凌草多糖的基本骨架得到保留，单糖种类未发生改变，但其分解温度降低、稳定性下降，多糖形貌也发生明显变化，球状与条状形貌增多，片状形貌减少。此外，在体外抗氧化性实验中，当硒多糖质量浓度为1.6mg/mL时，对DPPH自由基、ABTS自由基、羟自由基清除率分别为68.68%、86.69%、45.12%，均强于冬凌草多糖。