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91.
目的:制备北沙参多糖及其铁配合物,对其理化性质、结构特征和生物活性进行研究。方法:采用水提醇沉法制备北沙参多糖,经三氯化铁共热合成得到多糖铁配合物,利用紫外-可见光谱、红外光谱、高效阴离子交换色谱、透射电镜、差热-热重联用热分析仪等对多糖及其铁配合物的理化性质和结构特征进行测定,并考察其清除羟自由基和对α-葡萄糖苷酶的抑制作用。结果:北沙参多糖的提取率为18.4%,是由葡萄糖和甘露糖组成,其物质的量比为1.00∶4.25,制备得到的多糖铁配合物中铁离子质量分数为19.31%,是以聚合的β-FeOOH微核为核心,多糖在其表面配合形成的多糖铁(Fe3+)表面配合物。结果表明,北沙参多糖及其铁配合物均具有清除羟自由基和对α-葡萄糖苷酶的抑制作用,且经铁修饰后的多糖对羟自由基清除作用和对α-葡萄糖苷酶的抑制能力明显增强。结论:北沙参多糖经铁修饰后,对羟自由基清除作用和对α-葡萄糖苷酶的抑制能力均得到提高。 相似文献
92.
The electrochemical oxidation of hydroquinone and substituted hydroquinones has been studied over graphite and platinum electrodes in different alcohol media. The results have shown that good yields of the corresponding alkoxy-substituted phenols can be obtained with high selectivities towards the hydroquinone monoalkyl ether. A mechanism is put forward to explain the formation of the alkoxyphenol through the creation of a quinhydrone complex, formed between the hydroquinone and benzoquinone, which is then attacked by the alcohol acting as a nucleophile.In this study, the effect of sulfuric acid as supporting electrolyte and acid catalyst was compared with that of methanesulfonic acid. It was found that sulfuric acid gave the best yield for different alkoxyphenols. The alcohols under investigation were C1-C8, and it was found that the longer the chain length of the alcohol, the slower the tendency to produce alkoxyphenols. Branched alcohols such as secondary and tertiary alcohols showed no reactivity towards the quinhydrone complex. Some of the yields obtained are as follows: 4-methoxyphenol (97%), 4-ethoxyphenol (71.4%) and 4-propoxyphenol (81.1%). 相似文献
93.
朱小树 《化学推进剂与高分子材料》2007,5(1):65-66
介绍了一种含环氧基聚酯的羟值测定方法,即乙酰氯法。通过对其酰化原理分析,选用乙酰氯作酰化剂、二氯甲烷作酰化溶剂,测定含环氧基聚酯的羟值。结果发现无抱团现象,测定结果误差较小。 相似文献
94.
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96.
K. Hanaoka 《Journal of Applied Electrochemistry》2001,31(12):1307-1313
Antioxidant vitamins and enzymes such as superoxide dismutase, catalase and glutathione peroxidase are considered to function as scavengers against reactive oxygen species and to provide protection against reactive oxygen species, including free radicals. Although antioxidants such as L-ascorbic acid, d-catechin and quercetin dehydrate show superoxide dismutation activity, using reduced water produced in the cathode side by electrolysis as a solvent instead of 2 mM NaC1 solution of the same pH level as the reduced water increased the superoxide dismutation activity of these antioxidants. Moreover, neither the reduced water nor its electrolyte solution showed any superoxide dismutation activity by itself. On the other hand, the reduced water was able to decrease hydrogen peroxide levels. It has been found that the behaviour of H2 in reduced water, which was activated by a platinum electrode, differed from that of H2 introduced by bubbling of hydrogen gas. The former decreased H2O2, whereas the latter did not. These results suggest strongly that the increase in superoxide dismutation activity, with a proton donor such as L-ascorbic acid, is due to an increase in the dissociation activity of water while the scavenging activity for H2O2 is due to activated dissolved H2 in the reduced water. 相似文献
97.
Moldavian balm (Dracocephalum moldavica L., Lamiaceae) is a perennial herb native to central Asia and naturalized in eastern and central Europe. It is commonly consumed as a food-related product and as a herbal preparation because of its reputed medicinal properties. Despite its importance, few reports exist in the literature regarding the chemistry or antioxidant activity of this species. In this study, the aerial material of Moldavian balm collected from Iran was extracted by Soxhlet using seven solvents of different polarity, viz., petroleum ether, dichloromethane, acetonitrile, ethyl acetate, methanol, n-butanol and water. The qualitative-quantitative chemical composition of each extract was determined using high-performance liquid chromatography coupled to photodiode array detection. For each extract, the total phenolic content was estimated as was the in vitro antioxidant activity using the iron(III) reduction assay, the β-carotene-linoleic acid bleaching assay and the 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonate) free radical scavenging assays. Hydroxylated cinnamic acids, their derivatives and flavonoids were identified and quantified within the extracts, with rosmarinic acid being the most abundant component identified. The extracts demonstrated different degrees of potency within each assay, however, the observed pattern was not necessarily replicated between assays indicating the importance of the use of more than one screening technique to estimate the antioxidant activity of plant extracts. 相似文献
98.
99.
类黄酮的最新研究进展(Ⅰ)--抗氧化研究 总被引:4,自引:0,他引:4
综述了目前有关类黄铜的抗氧化研究进展,包括淬灭单线态氧、消除不同自由基(如羟自由基、过氧化物等)、抗脂质氧化活性以及类黄铜酚羟自由基的稳定性等.还概述了类黄酮的结构与抗氧化活性的相关性. 相似文献
100.
石榴皮提取物体外抗氧化活性比较研究 总被引:2,自引:0,他引:2
研究石榴皮提取物的体外抗氧化作用。采用羟自由基(.OH)、超氧阴离子自由基(.O2-)、2,2-二苯代苦味酰基自由基(DPPH.)的生成体系,研究石榴皮提取物及绿茶多酚、没食子酸为对照,对自由基的清除能力和对小鼠肝组织匀浆脂质过氧化抑制作用。结果表明:石榴皮提取物对羟自由基、超氧阴离子、DPPH.的半清除率分别为I:C50=71.37 mg/mL、SC50=557.55 mg/mL、DC50=31.98 mg/mL;没食子酸对这3种自由基的半清除率分别为I:C50=51.85 mg/mL、SC50=289.2 mg/mL、DC50=37.65 mg/mL;绿茶多酚对这3种自由基的半清除率分别为:IC50=66.67 mg/mL、SC50=1043.91 mg/mL、DC50=22.48 mg/mL。石榴皮提取物对小鼠肝组织匀浆的脂质过氧化半抑制率EC50=5.21 mg/mL、没食子酸半抑制率EC50=22.82 mg/mL、绿茶多酚半抑制率EC50=3.47 mg/mL。研究表明石榴皮提取物较没食子酸和绿茶多酚具有良好的清除自由基及抑制脂质过氧化的能力。石榴皮提取物能有效清除羟自由基、超氧阴离子自由基、DPPH.自由基,抑制脂质过氧化作用,具有进一步研究和开发价值。 相似文献