Antimutagenic activity of natural phenolic compounds present in the common bean ( Phaseolus vulgaris ) against aflatoxin B 1

Polyphenols with antimutagenic and anticarcinogenic properties are present in fruits, vegetables and legumes. In this study, the Salmonella typhimurium tester strains TA98 and TA100 were used in the microsuspension assay to examine the antimutagenic effect of phenolic compounds extracted from the common bean (Phaseolus vulgaris) against mutagenicity induced by aflatoxin B 1 (AFB 1 ). A dose-response curve was constructed for AFB 1 ; from which a level of 40ng AFB 1 /tube was selected for all antimutagenicity assays. The AFB 1 and phenolic extract (PE) were not toxic to the bacteria at concentrations tested. In the case of PE, results were similar to the number of spontaneous revertants for TA98 and TA100. The inhibitory effect of PE against AFB 1 mutagenicity was dose-dependent at the lower concentrations tested (2.5, 5, 10, 12.5, 15 and 25 μg-equivalent ( + )-catechin/tube for TA98; 0.5, 1, 1.5, 2.5, 5, 10 and 25 μg-equivalent ( + )-catechin/ tube for TA100). Further, a two-stage incubation procedure was used to investigate the potential interaction between PE and AFB 1 . The greatest inhibitory effect of the PE on AFB 1 mutagenicity occurred when PE and AFB 1 were incubated together. When the bacteria were first incubated with PE followed by a second incubation with AFB 1 , lower inhibition was observed. Lower inhibition was also observed when the bacteria were first incubated with AFB 1 followed by a second incubation with PE. The results suggest that the mechanism of inhibition could involve the formation of a chemical complex between of PE and AFB 1 .     

三聚氰胺甲醛树脂合成与性能的研究

本文针对三聚氰胺甲醛树脂合成与性能上存在的几个问题，从理论和实践上进行了讨论。     

The Chemistry of Water Treatment Processes Involving Ozone,Hydrogen Peroxide and Ultraviolet Radiation

Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O₃ at high pH, 0₃/H₂0₂, O₃/UV and H₂O₂/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O₃/UV process, the effect of the H₂0₂:0₃ ratio in the O₃/H₂O₂ process, and the impact of the low extinction coefficient of H₂O₂ in the H₂0₂/UV process.     

Interactions Between Ozone,Halogens and Organic Compounds

During drinking-water treatment, ozone used as a preoxidant and chlorine required for final disinfection, lead to competing chemical reactions, in the case of raw water containing both organic compounds and inorganic salts (such as bromides and ammonia).

The study of the interactions between those reactants has been made according to the following main topics :

As for THM formation, experiments conducted on simple organic compounds or on natural fulvic acids show important decreases in THM or TCAA formation after ozonation. It may be noticed, however, that the ozonation of surface waters may induce the formation of haloform precursors, usually with a low level of reactivity.

In water supplies containing bromide ions, oxidation of the latter through hypobromous acid may take place during the ozonation stage. Failing preozonation treatment, hypobromous acid is generated very rapidly during chlorination, thus inducing the formation of chloro- brominated organic compounds.

During the ozonation of fulvic acid solutions, the presence of small amounts of bicarbonate was found to improve precursor removal significantly.

It can be concluded that the partial analogy of the action of ozone or chlorine on aromatic structures, whether simple or complex (such as humic and fulvic acids), seems to indicate that the consequence of preozonation is the destruction, at least in part, of the most reactive sites for THM production, thus leading to a decrease of the volatile organochlorinated compounds formed during the post-chlorination. However, some ozonation products of natural waters are THM precursors, though of low reactivity. Then, in the presence of bromide ions, the formation of volatile organobrominated compounds may be observed during ozonation.     

车用聚丙烯改性材料气味分析及改善措施

针对改性的聚丙烯(PP)材料,探讨了基体PP树脂、吸附剂、后处理工艺以及加香对PP改性材料气味的影响.研究结果表明,选用氢调法PP树脂制得的PP改性材料气味性能优于降解法;吸附剂能一定程度继续提升PP气味;同时材料的后处理对PP改性材料的气味提升有积极作用;最后通过加香措施对PP改性材料味型进行适当的调整,最终改善后的...     

5083Al/1060Al/TA1/Ni/SUS304五层爆炸复合板退火组织演化及力学性能

为改善5083Al和304不锈钢爆炸焊接质量,提升隔热效果,本研究采用1060Al、TA1和Ni作夹层材料,制备了具有热传导梯度的五层爆炸复合板。为消除爆炸焊接后的残余应力,减少绝热剪切带和微裂纹等缺陷,采用550℃×60min退火工艺对五层爆炸复合板进行退火处理,并通过SEM、EBSD和万能试验机等手段,分析研究退火对其组织演化及力学性能的影响。结果表明：五层爆炸复合板的4个焊接界面均呈波形,且在界面处存在微裂纹、孔洞、绝热剪切带和漩涡区等缺陷。经退火处理,4个焊接界面均发生不同程度的再结晶,微裂纹、绝热剪切带等缺陷得到有效改善;5083Al/1060Al/TA1界面的β相和Al-Ti金属间化合物增多,TA1/Ni界面在原TiNi₃熔化层的基础上新增TiNi熔化层和Ti₂Ni熔化层。界面抗拉剪强度均有所降低,但均仍远高于相应国标使用要求;拉脱试样在5083Al/1060Al界面断裂分离。     

白厚漆中挥发性有机物的吹扫捕集/气相色谱-质谱分析方法研究

采用吹扫捕集/气相色谱-质谱法(PT/GC-MS)建立了白厚漆中挥发性有机物的快速分析方法。在优化吹扫捕集和气相色谱-质谱参数的基础上,在白厚漆中共鉴别出34个挥发性有机物成分。该方法简便、快捷、灵敏,适用于白厚漆中挥发性有机物的分析,并为白厚漆对水质和环境的影响研究提供理论依据。     

聚羟基铝无机化合物中羟基的测定

现行的测定聚羟基铝无机化合物中羟基的方法,由于未能准确确定反应等当点,因而重复性不好,准确性也受影响。本方法采用模拟的方式确定各种条件下的反应等当点,作为滴定终点的指示,从而大大提高了测定的准确性。     

Effects of Enhanced UV-B Radiation on Plant Chemistry: Nutritional Consequences for a Specialist and Generalist Lagomorph

Ultraviolet-B (UV-B) radiation has been increasing in temperate latitudes in recent decades and is expected to continue rising for some time. Enhanced UV-B radiation can change plant chemistry, yet the effects of these changes on mammalian herbivores are unknown. To examine the influence of enhanced UV-B radiation on nutrition of a specialist and generalist hindgut fermenter, we measured nutritional and chemical constituents of three common North American range plants, big sagebrush (Artemisia tridentata), yarrow (Achillea millefolium), and bluebunch wheatgrass (Pseudoregneria spicata), and how these changes influenced in vitro dry matter digestibility and in vivo digestibility by pygmy rabbits (Brachylagus idahoensis) and eastern cottontails (Sylvilagus floridanus). Forages were irradiated for 3 mo with ambient (1×) or supplemental (1.6×) UV-B radiation representing a 15% ozone depletion for Pullman, WA, USA. Enhanced UV-B radiation had minimal effects on the nutritional content and the tannin-binding capacity of forages. Similarly, the terpene concentration in sagebrush and yarrow was not affected by higher UV-B irradiances. Flavonoid compounds increased in sagebrush but decreased in yarrow. Rabbit preference and intake was not affected by treatment levels for any forage species and no differences were found between treatments for dry matter, fiber, protein digestibility, and apparent digestible energy.     

Molecular design of anti-biofouling materials from natural phenolic compounds

Many natural phenolic compounds found in plants are well known for their antibiotic and antioxidant activities. It has been hypothesized that these activities of natural phenols could be used for developing permanent anti-biofouling coatings. In this study, two phenolic components, anacardic acid and cardanol, were extracted from cashew nut shell liquid, and tested for their antibiotic and anti-biofouling activities against Pseudomonas fluorescens. Both compounds killed all the cells within 18 hours (anacardic acid) and 30 hours (cardanol) after the addition to the culture media at a concentration of 800 μg/ml. To form a stable permanent coating of these compounds, first they were polymerized by enzymatic polymerization, and the polymers were cross-linked on a glass slide. P. fluorescens were cultured on the coated and uncoated glasses for two weeks, and the images of the cells grown on the surfaces were taken by SEM. The coated surfaces clearly demonstrated anti-biofouling activities, showing not only fewer numbers of cells but also less exopolymer than the uncoated surfaces. Based on these results, a phenolic compound with a similar structure of anacardic acid was synthesized by using propylene diamine and fluorocarboxylic acid with cardanol. The synthesized phenolic compound was polymerized and cross-linked on a glass slide to test the anti-biofouling activity. The SEM images of the cells on the coated surface showed considerable decreases in the number of adhered cells and the amount of exopolymers even more than the anacardic acid and cardanol coatings. It is thought that the natural phenolic compounds with active functional groups can be used for anti-biofouling agents. This paper is dedicated to Prof. Chang Kyun Choi for celebrating his retirement from the School of chemical and biological engineering of Seoul National University.