Free radical involvement in the oxidation of Victorian brown coal

Electron spin resonance spectroscopy has been used to investigate free radical involvement in the oxidation of Victorian brown coal. Fresh, wet Yallourn brown coal exhibits two superimposed e.s.r. signals due to organic free radicals. The free radicals responsible for the narrow signal interact reversibly with atmospheric oxygen while the broad signal changes intensity dramatically during prolonged exposure to air. Coal:oxygen complex formation may explain these observations. Results also suggest that the free radical content of brown coal increases as a consequence of vacuum drying.     

Free radicals in coal and coal conversions. 8. Experimental determination of conversion in hydroliquefaction

The results of conversion determinations on the products from Powhatan No.5 coal liquefied in an autoclave and in a high-pressure, high-temperature e.s.r. cavity are reported. Oil, asphaltene and preasphaltene yields, and overall conversion have been determined for Powhatan No.5 coal samples liquefied in tetralin, SRC-11 heavy distillate, and naphthalene at temperatures from 400 to 480 ° C in both reactor systems. The concept of reaction severity is introduced and used to formalize the relation between the effect of temperature and reaction time on oil yield and conversion. Oil is the predominant product in liquefaction in tetralin or naphthalene, asphaltene is the major product of liquefaction in SRC-II heavy distillate. Retrogressive reaction (THF-insoluble product formation) becomes severe when SRC-II heavy distillate is the liquefaction solvent and residence time of >10 min are used at temperatures >450 °C. Preasphaltenes appear to be the only intermediate species in Powhatan No.5 liquefaction.     

新型选择性减害滤棒的研制

为了利用天然植物活性成分的抗氧化性,对抗氧化剂葡萄多酚(PT)、苹果多酚(PG)、茶多酚(CY)进行了筛选,采取直接添加、依托载体添加及制备成颗粒复合添加等多种添加工艺,并通过对抗氧化剂改性提高其在卷烟中的添加量,制备了新型选择性减害滤棒并卷制成样品烟支,对滤棒的各项常规物理指标和卷烟烟气的常规化学指标及自由基含量的变化进行测试。同时,采用加速氧化法对该种减害滤棒的抗氧化性能的稳定性进行了检测和评价。结果表明:采用直接添加和复合添加相结合的加工工艺,当有效成分含量为90%的改性抗氧化剂CY1在滤棒中的添加量达到3.0mg/支后,能够实现选择性显著降低烟气自由基近30%,同时不影响烟支外观和烟气常规技术指标,卷烟吸味也未因此有明显改变。     

竹叶特种氨基酸的存在及其生物学意义

在竹叶及其提取物中检出了相当含量的一种羟化赖氨酸—δ－ＯＨ－Ｌｙｓ，主要以游离单体和小肽的形式存在。从桂竹和金毛竹叶样分别测得其含量占干叶氨基酸总量的１．３３％和１．４０％，约相当于其中Ｌｙｓ含量的１／４．醇－水提取的过程有富集δ－ＯＨ－Ｌｙｓ的作用，其在提取物中的含量远远高于Ｌｙｓ．这一特殊的非蛋白氨基酸以相当含量存在于竹叶中，可能有着特殊的生物学意义。     

Free‐radical scavenging activity of wormwood (Artemisia absinthium L) extracts

In an effort to discover new antioxidant natural compounds, wormwood (Artemisia absinthium L) an aromatic‐bitter herb, was screened. The sequential extraction was realized with five solvents of different polarities (70% methanol, petroleum ether, chloroform, ethyl acetate, n‐butanol). The antioxidative activity was tested by measuring their ability to scavenge stable 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical and reactive hydroxyl radical during the Fenton reaction trapped by 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO), using electron spin resonance (ESR) spectroscopy. Results demonstrated that the antiradical and antioxidative activity depend on the type and concentration of applied extracts and increased in the order ethyl acetate > methanol > n‐butanol > chloroform > petroleum ether > remaining water extracts. The investigation showed that the antiradical activity increased with increasing concentration of all extracts. The high contents of total phenolic compounds (25.6 mg g^?1) and total flavonoids (13.06 mg g^?1) indicated that these compounds contribute to the antiradical and antioxidative activity. In a model system, the formation of o‐semiquinone radicals from quercetin and chlorogenic acid was obtained to prove the mechanism (hydrogen donating and/or one‐electron reduction) of free‐radical scavenging activity. Copyright © 2004 Society of Chemical Industry     

超声波-酶解法和超声波法提取裙带菜多糖的比较研究

比较研究超声波-酶解法和超声波法提取裙带菜多糖,并采用Fenton体系研究裙带菜中多糖对羟自由基清除活性作用。选取浸提时间、酶用量、固液比及温度4因素采用L16(45)和L9(34)两个方案分别对超声-酶解提取裙带菜多糖和超声波法提取进行正交试验。得到最佳的提取条件为：超声-酶解提取的裙带菜多糖得率与抗羟自由基优化组合为超声-酶解时间15min、纤维素酶用量2.8×104U/g(酶与藻粉比值)、温度70℃、固液比1:80为最佳条件,在此条件下,裙带菜多糖提取率为(4.522±0.028)%,3.60g/L的裙带菜多糖对羟自由基清除率为(51.70±0.47)%。超声-酶解结合方法提取试验条件对裙带菜多糖提取率影响显著(P＜0.01)。试验条件对提取得到的裙带菜多糖羟自由基清除率结果影响不显著(P＞0.05)。超声-酶解法的裙带菜多糖提取效果和及其羟自由基清除率能力明显优于超声波法,其结果具有显著性差异(P＜0.01)。超声波-酶解结合方法提取裙带菜多糖,提取效率高,多糖清除自由基效果好。     

超声波辅助提取甘草总黄酮及其抗氧化性

采用正交设计试验优化甘草总黄酮提取工艺,并研究其自由基清除活性。结果显示:超声波辅助提取甘草总黄酮的最佳提取工艺:乙醇浓度为75%、料液比为1∶25、超声频率为350 W,超声时间为25 min。总黄酮得率为1.943%;甘草总黄酮对自由基的清除能力随浓度的增大而增强,当溶液浓度达到1.1296mg/mL时,甘草总黄酮对羟自由基(.OH)的清除率达到了55.73%,对超氧自由基(O2-.)的清除率达到50%。甘草总黄酮是一种天然有效的自由基清除剂,具有一定的抗氧化活性。     

Effects of Light, Oxygen, and pH on the Absorbance of 2,2-Diphenyl-1-picrylhydrazyl

ABSTRACT: The absorbance of 2,2-diphenyl-1-picrylhydrazyl (DPPH) at 517 nm in methanol and acetone decreased by 20 and 35% for 120 min at 25 °C under light, respectively; in the dark it did not change significantly for 150 min. Decomposition of DPPH under 21% oxygen after 90 min under light was significantly higher than that under 1% oxygen. Absorbance of DPPH in pH 4 buffer solution in methanol, and in pH 10 buffer solution in acetone, decreased by 55 and 80%, respectively, under light for 120 min. The evaluation of antioxidant activity by the changes of DPPH absorbance should be carefully interpreted since the absorbance of DPPH at 517 nm is decreased by light, oxygen, pH, and type of solvent in addition to the antioxidant.     

Studies on antioxidant activities of mucuna seed (Mucuna pruriens var utilis) extract and various non‐protein amino/imino acids through in vitro models

The antioxidant activities of a methanolic extract of mucuna beans (Mucuna pruriens var utilis) and several non‐protein amino/imino acids, namely L ‐3,4‐dihydroxyphenylalanine (L ‐dopa), L ‐3‐carboxy‐6,7‐dihydroxy‐1,2,3,4‐tetrahydroisoquinoline (compound I), (?)‐1‐methyl‐3‐carboxy‐6,7‐dihydroxy‐1,2,3,4‐tetrahydroisoquinoline (compound II) and 5‐hydroxytryptophan (5‐HTP), were evaluated. By virtue of their hydrogen‐donating ability, all the tested compounds and the mucuna seed extract showed excellent reducing power, with the highest values being recorded for L ‐dopa in a dose‐dependent manner. Similarly, as compared with synthetic antioxidants (BHT and BHA) and quercetin, all the tested compounds and the seed extract were found to be more potent in free radical‐scavenging activity (P < 0.05) against α,α‐diphenyl‐β‐picrylhydrazyl (DPPH^?) radicals. Hydroxyl radicals (OH^?) and superoxide anion radicals (O₂^??) were effectively scavenged by the tested compounds, with the exception that no scavenging activity of 5‐HTP was observed on (O₂^??) up to a concentration of 2 mg ml^?1, as was also the case for BHA. Among the tested non‐protein amino/imino acids and seed extract the highest peroxidation‐inhibiting activity (95%) was recorded for 5‐HTP. On the other hand, in the linoleic acid/β‐carotene‐bleaching system, L ‐dopa, compound I and compound II acted as pro‐oxidants, whereas the seed extract showed only weak antioxidant activity as in the linoleic acid emulsion system. Copyright © 2003 Society of Chemical Industry     

糯米酶解工艺以及抗氧化活性研究

使用4种蛋白酶水解白糯米,以羟自由基清除率作为指标,选取中性蛋白酶作为水解用酶。考察了蛋白质底物浓度、酶添加量、酶解温度、初始pH 4种因素对于中性蛋白酶糯米酶解液羟自由基捕获能力的影响。在单因素实验基础之上,使用L9(34)正交优化试验设计,确定酶解液具有最高抗氧化能力的酶解工艺条件。优化后的工艺参数为底物浓度2%,酶添加量24 000 U/g(以蛋白质计),酶解温度55℃,pH8,作用时间0.5 h。在该条件下羟自由基清除率平均值可达56.05%。底物浓度、酶添加量、温度以及pH 4种因素对于羟自由基(.OH)清除率差异影响均极显著。糯米酶解液中的抗氧化肽等成分在60℃～100℃的温度范围内活性保持很好。