Mechanism of Antimicrobial Effect of Quinone Compounds

It has been observed that, in the culture medium, the toxicity of p-benzoquinone on bakers’ yeast decreases with time, and the decreasing process was examined from the view point of chemical reaction of quinone with the component of the medium.

As a result, it was shown that quinone concentration decreases by its 1,4-addition reaction with amino radicals of the component of the medium, and it was concluded that the inhibiting effect of quinone on the yeast growth is determined by the velocity of death of the yeast by the toxicity of quinone and that of inactivation of the toxicity by the addition reaction.     

Antimicrobial Browning-Inhibitory Effect of Flavor Compounds in Seaweeds

Since ancient times, the antimicrobial properties of seaweeds have been recognized. However, antimicrobial activities of volatile compounds in seaweeds have not been explored so far. Here, essential oils from seaweeds including green, brown and red algae such as Laminaria japonica, Kjellmaniella crassifolia, Gracilaria verrucosa and Ulva pertusa were prepared by using SDE (simultaneous distillation and extraction) apparatus. Volatile compounds in the essential oils were identified as aldehydes, ketones, carboxylic acids, alcohols and hydrocarbons by comparison of GC-retention times and MS data with those of authentic specimens. Flavor compounds such as (3Z)-hexenal, (2E)-hexenal and (2E)-nonenal in some essential oils showed strong antimicrobial activities against Escherichia coli TG-1, and Erwinia carotovora. Inhibition of browning can be achieved during either of two stages, namely, oxidation reaction by tyrosinase or subsequent non-enzymatic polymerization. Tyrosinase activity was measured by monitoring absorbance at 475 nm originating from dopachrome formed from L-DOPA. Many kinds of aliphatic carboxylic acids, aldehydes and alcohols were used as inhibitors for PPO activity. The results indicated that the α,β-unsaturated carbonyl compounds strongly inhibit tyrosinase activity. When seaweeds are damaged or macerated, the α,β-unsaturated aldehydes such as (2E)-hexenal and (2E)-nonenal are biosynthesized via the corresponding (3Z)-unsaturated aldehydes from linolenic acid and arachidonic acid. The flavor compounds that are formed could be valuable as safe antimicrobial browning-inhibitory agents of edible seaweed origin.     

Antimicrobial Compounds from Drypetes staudtii

Antimicrobial‐directed phytochemical investigation of the MeOH extract of Drypetes staudtii afforded two new compounds, 4,5‐(methylenedioxy)‐o‐coumaroylputrescine ( 1 ), 4,5‐(methylenedioxy)‐o‐coumaroyl‐4′‐N‐methylputrescine ( 2 ), along with seven known natural products 4α‐hydroxyeremophila‐1,9‐diene‐3,8‐dione ( 3 ), drypemolundein B ( 4 ), friedelan‐3β‐ol ( 5 ), erythrodiol ( 6 ), ursolic acid ( 7 ), p‐coumaric acid ( 8 ), and β‐sitosterol ( 9 ). Structures of compounds 1 – 9 were elucidated with the aid of extensive NMR and mass spectral studies. All of the isolates exhibited antibacterial activity against Gram‐positive and Gram‐negative bacteria with minimum inhibitory concentration (MIC) in the range of 8 – 128 μg/ml. Compounds 1 – 2 were also moderately active against Candida albicans with an MIC value of 32 μg/ml.     

新疆家蚕抗菌肽抗菌作用的超微结构观察及抗菌机理初探

为探讨基因工程表达的新疆家蚕(Bombyx mori)抗菌肽(cecropin-XJ)的抗菌机制,通过紫外分光光度法研究抗菌肽的抑菌动力学,并采用透射电镜观察抗菌肽作用于金黄色葡萄球菌(Staphylococcus aureus)后的超微结构,对抗菌肽抗菌机理进行初步探讨。结果表明,抗菌肽抑菌作用比较明显,抗菌肽的活性与作用时间有关。抗菌肽可能是通过"桶-板"模式渗透细胞膜,从而影响细胞膜的结构和功能,使细胞膜形成许多孔道,增强了金黄色葡萄球菌细胞的通透性,造成细胞内的原生质扩散,并从孔道向胞外渗漏,影响了细菌的代谢系统,从而起到抑菌、杀菌作用。抗菌肽使金黄色葡萄球菌细胞内容物大量渗漏而死亡,死亡细胞的细胞壁保持完整,表明细胞膜是抗菌肽作用的主要靶位点。     

Biofilm-Specific Cross-Species Induction of Antimicrobial Compounds in Bacilli

An air-membrane surface (AMS) bioreactor was designed to allow bacteria to grow attached to a surface as a biofilm in contact with air. When Bacillus licheniformis strain EI-34-6, isolated from the surface of a marine alga, was grown in this reactor, cells produced antimicrobial compounds which they did not produce when they were grown in shake flask cultures. An unidentified red pigment was also produced by surface-grown cells but not by planktonically grown cells. Glycerol and ferric iron were important for the production of antimicrobial compounds and the red pigment. Release of these secondary metabolites was not due to the onset of sporulation. Cell-free spent medium recovered from beneath the reactor membrane could induce production of antimicrobial compounds and red pigment in shake flask cultures. Neither glycerol nor ferric iron was required for production of these inducer compounds. Spent medium from beneath the membrane of an AMS bioreactor culture of Bacillus subtilis strain DSM10^T and Bacillus pumilus strain EI-25-8 could also induce production of antimicrobial compounds and a red pigment in B. licheniformis isolate EI-34-6 grown in shake flask cultures; however, the corresponding spent medium from shake flask cultures of DSM10^T and EI-25-8 could not. These results suggest that there is a biofilm-specific cross-species signaling system which can induce planktonically grown cells to behave as if they were in a biofilm by regulating the expression of pigments and antimicrobial compounds.     

Gas-Volume Measurement System for Evaluating Effectiveness of Antimicrobial Compounds

Yeast spoilage was followed by measuring gas volume produced inside a sealed bag of inoculated fruit. Volume of gas produced correlates with plate counts.     

黄酮类化合物抑制微生物活性及其作用机制

本文综述了黄酮类化合物抑制细菌、病毒和真菌的活性及可能的作用机制,黄酮类化合物结构与抑菌活性之间的关系。结果表明,黄酮类化合物主要通过抑制细菌DNA旋转酶,抑制细菌细胞质膜的功能,抑制细菌能量代谢等方面发挥抑菌功效。指出黄酮类化合物是今后抗病源微生物药物开发新的研究方向。     

鱼精蛋白抗菌机制的研究

鱼精蛋白是一种存在于各类动物精巢组织中的多聚阳离子肽,其抗菌性很早就被所知,然而它的抗菌机理却一直未能得到很清楚的了解。现存在的机理有2种:一种认为鱼精蛋白与细菌细胞壁结合,通过破坏细胞壁的形成来达到抑菌效果;另一种认为鱼精蛋白破坏了细胞能量的转换、营养物质的吸收功能,细胞质膜是鱼精蛋白攻击的对象。事实上,作者认为,鱼精蛋白的抗菌效果可能是通过以上2种方式共同作用的结果,因而它的抗菌机理也可能是这两种机理的叠加,这还需进一步的研究证明。     

Vitamin K, 2,3-Epoxide And Quinone Reduction: Mechanism And Inhibition

The chemical and enzymatic pathways of vitamin K₁ epoxide and quinone reduction have been investigated. The reduction of the epoxide by thiols is known to involve a thiol-adduct and a hydroxy vitamin K enolate intermediate which eliminates water to yield the quinone. Sodium borohydride treatment resulted in carbonyl reduction generating relatively stable compounds that did not proceed to quinone in the presence of base. NAD(P)H:quinone oxidoreductase (DT-diaphorase. E.C. I.6.99.2) reduction of vitamin K to the hydroquinone was a significant process in intact microsomes. but 1/5th the rate of the dithiothreitol (DTT)-dependent reduction. No evidence was found for DT-diaphorase catalyzed reduction of vitamin K₁ epoxide, nor was it capable of mediating transfer of electrons from NADH to the microsomal epoxide reducing enzyme. Purified diaphorase reduced detergent- solubilized vitamin K, 10^?5 as rapidly as it reduced dichlorophenylindophenol(DCPIP). Reduction of 10 μM vitamin K, by200 μM NADH was not inhibited by 10μM dicoumarol. whereas DCPIP reduction was fully inhibited. In contrast to vitamin K, (menadione). vitamin K₁ (phylloquinone) did not stimulate microsomal NADPH consumption in the presence or absence of dicoumarol. DTT-dependent vitamin K epoxide reduction and vitamin K reduction were shown to be mutually inhibitory reactions. suggesting that both occur at the same enzymatic site. On this basis, a mechanism for reduction of the quinone by thiols is proposed. Both the DTT-dependent reduction of vitamin K₁ epoxide and quinone. and the reduction of DCPIP by purified DT-diaphorase were inhibited by dicoumarol, warfarin. lapachol. and sulphaquinoxaline     

Preliminary Studies on the Relationship between Diterpene Quinone Compounds and Peroxidase Isozyme in the Labiatae

Peroxidase isozyme was determined by polyacrylamide gel column electrophoresis method in 18 species of the Labiatae. Results showed that the band of peroxidase isozyme of those species containing diterpene quinone compounds appeared in the middle of the column with an inclination to the anode. The contents of diterpene quinone compounds in the plant were usually consistant with the band of its peroxidase isozyme. The band of peroxidase isozyme of those species containing essential oil almost did not appear in the column under the same condition.     

Antimicrobial Activity of 3-Phenylimidazolidine-2,4-diones and Related Compounds

The structure-activity relationships of 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were investigated by the agar dilution method using Sclerotinia sclerotiorum as a test microbe. Several compounds were tested for antimicrobial spectrum in vitro with other pathogenic microbes and for foliage protective activity in green house tests with rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. It was found that the antimicrobial activity was enhanced when the 1-position of imidazolidine ring was substituted by an alkyl group but was reduced when the 5-position was substituted by alkyl groups. Generally, 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were active against Scierotiniaceae, Corticiaceae, Dematiaceae, Polystigmataceae or Pleosporaceae. In green house tests, some of these compounds showed high protective activity against rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. Results of the green house tests on the above mentioned diseases correlate well with those of in vitro tests except in the case of kidney bean stem rot.     

The Antimicrobial Mechanism of Action of Epsilon-Poly-l-Lysine

Epsilon-poly-l-lysine (ε-PL) is a natural antimicrobial cationic peptide which is generally regarded as safe (GRAS) as a food preservative. Although its antimicrobial activity is well documented, its mechanism of action is only vaguely described. The aim of this study was to clarify ε-PL''s mechanism of action using Escherichia coli and Listeria innocua as model organisms. We examined ε-PL''s effect on cell morphology and membrane integrity and used an array of E. coli deletion mutants to study how specific outer membrane components affected the action of ε-PL. We furthermore studied its interaction with lipid bilayers using membrane models. In vitro cell studies indicated that divalent cations and the heptose I and II phosphate groups in the lipopolysaccharide layer of E. coli are critical for ε-PL''s binding efficiency. ε-PL removed the lipopolysaccharide layer and affected cell morphology of E. coli, while L. innocua underwent minor morphological changes. Propidium iodide staining showed that ε-PL permeabilized the cytoplasmic membrane in both species, indicating the membrane as the site of attack. We compared the interaction with neutral or negatively charged membrane systems and showed that the interaction with ε-PL relied on negative charges on the membrane. Suspended membrane vesicles were disrupted by ε-PL, and a detergent-like disruption of E. coli membrane was confirmed by atomic force microscopy imaging of supported lipid bilayers. We hypothesize that ε-PL destabilizes membranes in a carpet-like mechanism by interacting with negatively charged phospholipid head groups, which displace divalent cations and enforce a negative curvature folding on membranes that leads to formation of vesicles/micelles.     

乳链菌肽作用机制及其应用

乳链菌肽作为高效、安全的天然食品防腐剂已得到广泛应用。成熟的乳链菌肽含有34个氨基酸残基,由5个硫醚桥组成独特的内环结构,是研究蛋白质结构与功能的一个很好的材料。本文论述了乳链菌肽的分子结构及其与细胞膜作用的分子机制,详细阐述了乳链菌肽的作用模型。     

Preparation of Antimicrobial Compounds by Hydrolysis of Oleuropein from Green Olives

Oleuropein, an intensely bitter glucoside, was isolated from green olives. Hydrolysis products obtained from oleuropein in sufficient quantity for further tests were: (i) beta-3,4-dihydroxyphenylethyl alcohol prepared by acid hydrolysis of oleuropein; (ii) elenolic acid obtained by methanolysis of oleuropein, isolation of the intermediate acetal, and subsequent acid hydrolysis; and (iii) oleuropein aglycone formed by the action of beta-glucosidase on the parent glucoside. Mass spectral verification of the isolated compounds and ultraviolet absorption data are given. Oleuropein and its aglycone had similar threshold levels for detection of bitterness, whereas elenolic acid and beta-3,4-dihydroxyphenylethyl alcohol were not judged to be bitter.     

复方中药制剂在寒冷诱导机体损伤中作用及其机制

目的:研究寒冷所诱导的机体损伤作用,明确寒冷引发机体损伤的部分机制以及预防性药物对机体处于寒冷环境中的保护作用。方法:通过低温试验、ATP检测、电镜观察等确定寒冷对机体造成的损伤;通过总抗氧化能力、CAT含量、谷胱甘肽过氧化物酶含量、SOD水平、MDA水平等的检测确定氧化应激在寒冷暴露对机体损伤中的作用及机制;并确证复方中药制剂在寒冷损伤氧化应激状态下对机体的保护作用。结果:1.急性-15±1℃寒冷环境暴露可引起机体内肝脏组织能量代谢障碍,ATP生成减少,肝细胞线粒体损伤,溶酶体增多等机体损伤的现象;2.寒冷应激可导致机体的总抗氧化能力、CAT显著减少,而氧化应激终产物之一的丙二醛(malondialdehyde,MDA)显著增多(说明肝脏组织出现明显的氧化应激过程),并且出现抗氧化能力下降。3.预先给予药物干预后,机体抗氧化能力显著增加。结论:1.寒冷可以诱导机体肝脏明显损伤。2.氧化应激是寒冷诱导机体损伤的关键机制之一。3.复方中药制剂可以增加机体在寒冷应激条件下的抗氧化能力,从而产生保护作用。     

植物内生真菌抗菌活性物质的研究进展

植物内生真菌是一种新的微生物资源,具有潜在的应用前景,能产生生物碱类、肽类、甾体类、萜类、酚类、醌类、脂肪族类、异香豆素类等多种类型的抗菌活性物质.本文简要综述了植物内生真菌的抗菌活性物质的研究方法、提取物的抗菌活性、抗菌活性成分等方面的研究进展.     

吡咯喹啉醌对苹果花粉萌发和花粉管生长的影响(简报)

在花粉萌发培养基上添加1～50μmol·L