Silphinene Sesquiterpenes as Model Insect Antifeedants

Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11-acetoxy-5-angeloyloxysilphinen-3-one (1), 11-acetoxy-5-tigloyloxysilphinen-3-one (2), 11-acetoxy-5-iso- butyryloxysilphinen-3-one (3), 11-hydroxy-5-angeloyloxysilphinen-3-one (4), 11,5-dihydroxysilphinen-3-one (5), 11,5-diacetoxysilphinen-3-one (6), 5,11-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect.     

Liquid-phase stereoselective thymol hydrogenation over supported nickel catalysts

The stereoselective hydrogenation of thymol was studied in liquid phase over several nickel catalysts, modified by coimpregnation of inorganic compounds containing chlorine. The total activity of all catalysts studied was decreased and was on the same order of magnitude, indicating that chlorine even after reduction remains on the surface and is responsible for the poisoning effects. Such blocking of accessible sites results in similar reaction rates for the catalysts studied. Selectivity and stereoselectivity to menthols and menthones changed significantly. The modifiers could influence the rate of keto-enol transformations, which is thought to be the key selectivity and stereoselectivity governing step.     

Evaluation of Antioxidative Constituents from Thyme

The non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidative activity. In addition to carvacrol ( II ) and thymol ( III ), p -cymene-2,3-diol (I ; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. The structure of I was elucidated using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and mass spectrometry. Antioxidative activity was investigated with the Rancimat method (100°C) and the Schaal test (60°C). Compound I exhibited the strongest antioxidative activity which was greater than that of α-tocopherol and butylated hydroxyanisole. Five thyme species were analysed by means of HPLC with electrochemical detection for the concentration of compounds I – III . The highest amounts of I – III were found in Thymus vulgaris L.     

不同有机物对硝酸盐氮测试的影响

研究了红糖、葡萄糖、乙酸钠、甲醇、乙醇、乙酸、丙酸、丁酸、正戊酸、混合有机溶剂等10种不同有机物对麝香草酚光谱法和离子色谱法测试硝酸盐氮的影响。结果表明,溶液中含有红糖或葡萄糖时,均会对麝香草酚法测试硝酸盐氮造成影响,使得测试结果偏大;在无硝酸根离子存在时,红糖和葡萄糖的质量浓度与硝酸盐氮的测试浓度非线性相关;而乙酸钠、甲醇、乙醇、乙酸、丙酸、丁酸、正戊酸和混合有机溶剂则对麝香草酚法测试硝酸盐氮没有影响。实验发现,红糖和葡萄糖在浓硫酸的作用下与麝香草酚发生Molisch反应,形成有色复合物和红棕色不溶性沉淀。实验采用离子色谱法测试硝酸盐氮时,红糖和葡萄糖等糖类有机物对测试结果均无影响。     

分光光度法测定发酵液中L-精氨酸含量

建立了定量测定发酵液中L-精氨酸含量的方法。以百里酚的次溴酸钠溶液为显色剂,用正丁醇萃取显色产物,以分光光度计比色测定有机相的吸光度值。测定发酵液中L-精氨酸的最佳条件为:取待测物稀释液5.0mL,依次加入0.03%的百里酚溶液2.0mL,0.7%的次溴酸钠溶液0.5mL,摇匀,30s内加入正丁醇5.0mL,除去水相;向有机相中加入0.4mL无水乙醇,室温放置1min,用分光光度计测定OD480。方法的检出限为2.5μg/mL,摩尔吸光系数ε为1.2×104L/(mol.cm),发酵液样品相对标准偏差为0.89%～1.10%,回收率为97.3%～102.0%。此方法简便、快速、准确可靠,适合用于发酵液中L-精氨酸含量的定量检测。     

百里香酚和肉桂醛联用对沙门氏菌的协同抑菌效应及其应用

研究了百里香酚和肉桂醛联用对沙门氏菌的抑菌效果,并将两者作为复配抗菌剂应用于盐焗鸡中以探究其保鲜效果。采用微量稀释法确定了百里香酚和肉桂醛对沙门氏菌的最小抑菌浓度及联合抑菌效果,结果显示百里香酚和肉桂醛的最小抑菌浓度均为0.25 mg/mL、最小杀菌浓度均为0.5 mg/mL;此外,两者联用时的分级抑菌浓度指数为0.75,表明百里香酚和肉桂醛具有较好的协同抑菌效应;该结论同样被时间-杀菌曲线、扫描电子显微镜、PI染色实验的结果所证实,百里香酚和肉桂醛联用可以显著地破坏沙门氏菌细胞膜的完整性,改变细菌形态,从而导致胞内物质泄漏、最终菌体裂解死亡,表明其具有一定的防腐保鲜应用潜力。因此,该研究以盐焗鸡作为食品模型从微生物和脂质氧化两方面探究了百里香酚和肉桂醛的防腐保鲜效果,结果显示百里香酚和肉桂醛联用可以显著地抑制盐焗鸡中细菌的增殖和脂质的氧化,表明百里香酚和肉桂醛联用可以作为一种天然复配抗菌剂应用于盐焗鸡等熟肉制品的保鲜中。     

Antimicrobial Effects of Vapor Phase Thymol,Modified Atmosphere,and Their Combination against Salmonella spp. on Raw Shrimp

Salmonella contamination on raw shrimp is a big food safety concern in the United States currently. This research evaluated the inhibition effects of vapor phase thymol, modified atmosphere (MA), and their combination against Salmonella spp. on raw shrimp. Growth profiles of a Salmonella spp. cocktail (6 strains), inoculated onto the surface of raw shrimp, treated with vapor phase thymol at 3 levels (0, 0.8, and 1.6 mg/L), or MA (59.5% CO₂ + 39.5% N₂ + 1% O₂), both alone and in combination, at 3 temperatures (8, 12, and 16 ºC), were determined. Lag time and maximum growth rate of Salmonella spp. under each treatment were obtained using Baranyi and Roberts models. Results indicated that both vapor phase thymol and MA treatments alone inhibited the growth potential of Salmonella spp. effectively, extending the lag time by 10% to 100% and reducing the maximum growth rate by 14% to 71% compared with controlled samples at experimental temperatures (8, 12, and 16 ºC). Combination treatments of vapor phase thymol and MA exhibited greater inhibition effectiveness than each individual treatment and a synergistic antimicrobial effectiveness could be observed on the lag time extension. To the maximum, at 12 ºC, lag time of Salmonella spp. was extended 59.6% more by the combination treatment of 0.8 mg/L thymol + MA (36.97 h) than those effects combined from 0.8 mg/L thymol treatment and MA treatment alone (23.16 h in total). This combination strategy could be potentially utilized for Salmonella inhibition during the long distance and temperature‐abused raw shrimp import process. Practical Application The vapor phase thymol + MA combination strategy could be potentially applied in temperature‐abused and long‐distance raw shrimp import process to retard the Salmonella spp. growth, therefore reducing its import rejection rate as well as enhancing its food safety level to the consumers’ concerns.     

麝香草酚和二磺酸酚分光光度法测定NO-3-N的比较

文章对两种测定NO3^-－N的方法从灵敏度、去Cl^-、NO2^-的干扰能力及实际操作作了比较，并提出了用麝香草酚测定NO3^--N应注意事项。     

丁香酚、香芹酚和百里香酚对禾谷镰刀菌的抑菌活性及机制

以转录组技术为基础,研究丁香酚、香芹酚和百里香酚对禾谷镰刀菌的抑制作用及作用机理。方法：借助体外抑菌实验测定丁香酚、香芹酚和百里香酚对禾谷镰刀菌菌丝生长、孢子萌发和呕吐毒素生物合成的有效作用浓度;通过测定丁香酚、香芹酚和百里香酚处理后菌丝液的电导率、ATP含量和丙二醛含量进一步从细胞水平探讨其作用位点;通过转录组学阐明丁香酚、香芹酚和百里香酚抑制禾谷镰刀菌生长和毒素合成的分子机制。结果：3 种植物精油活性成分中,百里香酚的抗真菌活性最强。丁香酚、香芹酚和百里香酚可破坏禾谷镰刀菌细胞膜完整性,引起电解质渗漏,能量代谢失衡。此外,3 种植物精油活性成分通过核糖体、线粒体结构和转录组水平上的酶合成发挥对禾谷镰刀菌的抑制作用。     

Natural compounds to preserve fresh fish burgers

Natural antimicrobial compounds to control the quality decay of a fresh fish burger were studied. In particular, thymol, lemon extract and grape fruit seed extract (GFSE), at 20, 40 and 80 ppm, have been tested against the main spoilage microorganisms inoculated in fish burgers stored at 5 °C. The evolution of mesophilic and psychrotrophic bacteria was also monitored. The sensorial quality decay was determined by means of a panel test, which assessed odour, colour, texture, drip loss and general appearance during the storage period. Results show that all the active substances efficiently slowed down the growth of the spoilage microorganisms. In particular, GFSE was the most efficient against Photobacterium phosphoreum , Shewanella putrefaciens and mesophilic bacteria, whereas thymol was the most efficient against both psychrotrophic bacteria and Pseudomonas fluorescens . Microbial growth was the factor limiting fresh fish burger acceptability.