Objective:To assess the antimicrobial and cytotoxic effects of Methylobacterium sp.isolated from soil sample of Doddabetta forest,Nilgiris,Western Ghats of Tamil Nadu.Methods:Isolation of Methylobacterium was performe...Objective:To assess the antimicrobial and cytotoxic effects of Methylobacterium sp.isolated from soil sample of Doddabetta forest,Nilgiris,Western Ghats of Tamil Nadu.Methods:Isolation of Methylobacterium was performed from soils by serial dilution plate technique.The strain was grown in modified nutrient gulucose agar(MNGA)medium to study the morphology and biochemical characteristics.Methylobacterium sp.was screened for its antimicrobial activity against pathogenic bacteria and fungi.The strain was subjected to 16S rRNA analysis and was identified as Methylohacterium sp.The nucleotide sequence of the 16S rRNA gene of the isolate exhibited close similarity with other Methylobacterium sp.and has been submitted to Genbank.The antibacterial substances were extracted using chloroform and ethyl acetate from MNGA medium in which ERI-135 had grown for 5 d at 30℃.Cytotoxic effect was also studied.GC-MS analysis was carried out.The antimicrobial activity was assessed using broth micro dilution technique.Results:Ethyl acetate extract showed activity against bacteria such as Bacillus subtilis,Klebsiella pneumoniae(K.pneumoniae),Pseudomonas aeruginosa,Salmonella typkimurium,Shigella flexneri,Enterobacter aerogenes,Staphylococcus aureu and Staphylococcus epidermidis(S.epidermidis)and fungi such as,Candida albicans and Trichophyton rubrum.The lowest minimum inhibitory concentrations were:250μg/mL against 5.epidermidis and 250μg/mL against K.pneumonia.The isolate had the ability to produce enzymes such as protease.The exyract showed cytotoxic effect in human adenocarcinoma cancer cell line(A549).GC-MS analysis showed the presence of isovaleric acid(3.64%),2-Methylbulanoic acid(5.03%),isobutyramide(5.05%),N,Noimethylformamide-di-t-butylacetal(9.79%),benzeneacetamide(15.56%),octyl butyl phthalate(3.59%)and diisooctyl phthalate(5.79)in the extract.Conclusions:Methylobaeterium sp.(ERI-135)showed promising antibacterial and cytotoxic activity.This is the first report in the antimicrobial and cytotoxic effect of Methylobaeterium sp.展开更多
饱和的碳氢键氧化是合成化学和化学工业中一类重要的化学反应.然而,饱和C(sp^(3))−H键离解能(BDEs)较高、极性较弱,导致了底物难以活化和催化转化效率较低等问题.在过去的几十年,C(sp^(3))−H键的定向活化转化取得了重要的进展.其中,关于...饱和的碳氢键氧化是合成化学和化学工业中一类重要的化学反应.然而,饱和C(sp^(3))−H键离解能(BDEs)较高、极性较弱,导致了底物难以活化和催化转化效率较低等问题.在过去的几十年,C(sp^(3))−H键的定向活化转化取得了重要的进展.其中,关于C(sp^(3))−H键催化氧化的研究主要涉及一些键能低的、预活化的C−H键,包括苄基型、亚甲基型、脂肪族X−CH_(2)(X=O,N)和甲苯等,含有未活化C(sp^(3))−H键的复杂化合物的选择性氧化仍具有挑战性.例如,芳基醚C(sp^(3))−H键功能化通常采用计量的过氧化物氧化剂,或者通过单电子氧化和碱促进的去质子化进一步构建C−C/C−N键,产物选择性较低,也带来了一些不利的环境影响.因此,有必要开发高效、温和的芳基醚C(sp^(3))−H键选择氧化方法,并将其应用于有机合成和药物开发.近年来,光催化C(sp^(3))−H键氧化因其操作简便、氧化还原中性等优点,已发展成为一种有用且多样的催化研究工具.本文发展了一种利用氧气作为氧化剂,在可见光驱动下选择性地将芳基醚C(sp^(3))−H键氧化成为甲酸苯酯类产物的新方法.使用Mes-10-phenyl-Acr^(+)−BF_(4)^(-)光催化剂,高效活化多种氯源(如盐酸、无机氯盐和有机氯化物)得到氯自由基,由于其具有较高的氧化能力(+2.03 V vs.SCE)和对氢原子的亲和力,能够通过氢原子转移过程活化芳基醚C(sp^(3))−键,攫取氢自由基得到相应的烷基碳自由基(•CH_(2)OPh)中间体,进一步被分子氧选择氧化得到酯类目标产物.研究结果表明,多种链状芳基醚和不同取代(如给电子基和吸电子基)芳基醚均可发生氧化反应,高收率地合成了一系列官能团丰富的甲酸苯酯类化合物.本文方法具有反应条件温和、操作简单、官能团耐受性好以及可规模化放大等优点,并且少量的水对反应没有明显影响.机理实验研究结果表明,芳基醚C(sp^(3))−H键的断裂是反应过程的决速步骤.紫外可见吸收光谱结果表明,氯离子与催化剂之间的相互作用强于底物,并且自由基捕获实验证实反应体系中存在氯自由基和烷基碳自由基物种,表明反应经历自由基路径.此外,电子顺磁共振测试结果表明,反应过程中存在单线态氧物种,可能是激发态的光催化剂直接与氧气发生能量转移得到;同位素实验(18O)揭示了甲酸苯酯类化合物氧的来源.综上,本文实现了温和条件下光催化芳基醚C(sp^(3))−H键选择氧化反应,高收率合成了一系列甲酸苯酯类化合物.该方法避免了化学计量的过氧化物和碱等添加剂的使用以及底物的过度氧化,阐明了催化反应机制,为其他醚类化合物的C(sp^(3))−H键氧化功能化提供了新思路,为后续化学合成和药物开发提供了参考和启示.展开更多
基金Supported by Entomology Research Institute.Loyolacollege,Chennai,Tamil Nadu,India(Grant No.ER1/2011/MB-05)
文摘Objective:To assess the antimicrobial and cytotoxic effects of Methylobacterium sp.isolated from soil sample of Doddabetta forest,Nilgiris,Western Ghats of Tamil Nadu.Methods:Isolation of Methylobacterium was performed from soils by serial dilution plate technique.The strain was grown in modified nutrient gulucose agar(MNGA)medium to study the morphology and biochemical characteristics.Methylobacterium sp.was screened for its antimicrobial activity against pathogenic bacteria and fungi.The strain was subjected to 16S rRNA analysis and was identified as Methylohacterium sp.The nucleotide sequence of the 16S rRNA gene of the isolate exhibited close similarity with other Methylobacterium sp.and has been submitted to Genbank.The antibacterial substances were extracted using chloroform and ethyl acetate from MNGA medium in which ERI-135 had grown for 5 d at 30℃.Cytotoxic effect was also studied.GC-MS analysis was carried out.The antimicrobial activity was assessed using broth micro dilution technique.Results:Ethyl acetate extract showed activity against bacteria such as Bacillus subtilis,Klebsiella pneumoniae(K.pneumoniae),Pseudomonas aeruginosa,Salmonella typkimurium,Shigella flexneri,Enterobacter aerogenes,Staphylococcus aureu and Staphylococcus epidermidis(S.epidermidis)and fungi such as,Candida albicans and Trichophyton rubrum.The lowest minimum inhibitory concentrations were:250μg/mL against 5.epidermidis and 250μg/mL against K.pneumonia.The isolate had the ability to produce enzymes such as protease.The exyract showed cytotoxic effect in human adenocarcinoma cancer cell line(A549).GC-MS analysis showed the presence of isovaleric acid(3.64%),2-Methylbulanoic acid(5.03%),isobutyramide(5.05%),N,Noimethylformamide-di-t-butylacetal(9.79%),benzeneacetamide(15.56%),octyl butyl phthalate(3.59%)and diisooctyl phthalate(5.79)in the extract.Conclusions:Methylobaeterium sp.(ERI-135)showed promising antibacterial and cytotoxic activity.This is the first report in the antimicrobial and cytotoxic effect of Methylobaeterium sp.
文摘饱和的碳氢键氧化是合成化学和化学工业中一类重要的化学反应.然而,饱和C(sp^(3))−H键离解能(BDEs)较高、极性较弱,导致了底物难以活化和催化转化效率较低等问题.在过去的几十年,C(sp^(3))−H键的定向活化转化取得了重要的进展.其中,关于C(sp^(3))−H键催化氧化的研究主要涉及一些键能低的、预活化的C−H键,包括苄基型、亚甲基型、脂肪族X−CH_(2)(X=O,N)和甲苯等,含有未活化C(sp^(3))−H键的复杂化合物的选择性氧化仍具有挑战性.例如,芳基醚C(sp^(3))−H键功能化通常采用计量的过氧化物氧化剂,或者通过单电子氧化和碱促进的去质子化进一步构建C−C/C−N键,产物选择性较低,也带来了一些不利的环境影响.因此,有必要开发高效、温和的芳基醚C(sp^(3))−H键选择氧化方法,并将其应用于有机合成和药物开发.近年来,光催化C(sp^(3))−H键氧化因其操作简便、氧化还原中性等优点,已发展成为一种有用且多样的催化研究工具.本文发展了一种利用氧气作为氧化剂,在可见光驱动下选择性地将芳基醚C(sp^(3))−H键氧化成为甲酸苯酯类产物的新方法.使用Mes-10-phenyl-Acr^(+)−BF_(4)^(-)光催化剂,高效活化多种氯源(如盐酸、无机氯盐和有机氯化物)得到氯自由基,由于其具有较高的氧化能力(+2.03 V vs.SCE)和对氢原子的亲和力,能够通过氢原子转移过程活化芳基醚C(sp^(3))−键,攫取氢自由基得到相应的烷基碳自由基(•CH_(2)OPh)中间体,进一步被分子氧选择氧化得到酯类目标产物.研究结果表明,多种链状芳基醚和不同取代(如给电子基和吸电子基)芳基醚均可发生氧化反应,高收率地合成了一系列官能团丰富的甲酸苯酯类化合物.本文方法具有反应条件温和、操作简单、官能团耐受性好以及可规模化放大等优点,并且少量的水对反应没有明显影响.机理实验研究结果表明,芳基醚C(sp^(3))−H键的断裂是反应过程的决速步骤.紫外可见吸收光谱结果表明,氯离子与催化剂之间的相互作用强于底物,并且自由基捕获实验证实反应体系中存在氯自由基和烷基碳自由基物种,表明反应经历自由基路径.此外,电子顺磁共振测试结果表明,反应过程中存在单线态氧物种,可能是激发态的光催化剂直接与氧气发生能量转移得到;同位素实验(18O)揭示了甲酸苯酯类化合物氧的来源.综上,本文实现了温和条件下光催化芳基醚C(sp^(3))−H键选择氧化反应,高收率合成了一系列甲酸苯酯类化合物.该方法避免了化学计量的过氧化物和碱等添加剂的使用以及底物的过度氧化,阐明了催化反应机制,为其他醚类化合物的C(sp^(3))−H键氧化功能化提供了新思路,为后续化学合成和药物开发提供了参考和启示.
