Department of Drug and Food Control and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.
Folia Microbiol (Praha). 2012 Nov;57(6):501-8. doi: 10.1007/s12223-012-0164-z. Epub 2012 May 29.
The aim of present work was to study chemical structures and biological activities of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa MN1 isolated from oil-contaminated soil. The results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that total rhamnolipids (RLs) contained 16 rhamnolipid homologues. Di-lipid RLs containing C(10)-C(10) moieties were by far the most predominant congeners among mono-rhamnose (53.29 %) and di-rhamnose (23.52 %) homologues. Mono-rhamnolipids form 68.35 % of the total congeners in the RLs. Two major fractions were revealed in the thin layer chromatogram of produced RLs which were then purified by column chromatography. The retardation factors (R (f)) of the two rhamnolipid purple spots were 0.71 for RL1 and 0.46 for RL2. LC-MS/MS analysis proved that RL1 was composed of mono-RLs and RL2 consisted of di-RLs. RL1 was more surface-active with the critical micelle concentration (CMC) value of 15 mg/L and the surface tension of 25 mN/m at CMC. The results of biological assay showed that RL1 is a more potent antibacterial agent than RL2. All methicillin-resistant Staphylococcus aureus (MRSA) strains were inhibited by RLs that were independent of their antibiotic susceptibility patterns. RLs remarkably enhanced the activity of oxacillin against MRSA strains and lowered the minimum inhibitory concentrations of oxacillin to the range of 3.12-6.25 μg/mL.
本工作旨在研究从受污染土壤中分离出的铜绿假单胞菌 MN1 产生的鼠李糖脂生物表面活性剂的化学结构和生物活性。液相色谱-串联质谱（LC-MS/MS）分析结果表明，总鼠李糖脂（RLs）含有 16 种鼠李糖脂同系物。含有 C(10)-C(10) 部分的二酰基 RL 是单鼠李糖（53.29%）和二鼠李糖（23.52%）同系物中最主要的同系物。单鼠李糖脂构成 RLs 中总同系物的 68.35%。在产生的 RLs 的薄层色谱图中显示了两个主要馏分，然后通过柱色谱法对其进行纯化。两个鼠李糖脂紫色斑点的阻滞因子（R(f)）分别为 RL1 的 0.71 和 RL2 的 0.46。LC-MS/MS 分析证明 RL1 由单 RL 组成，RL2 由二 RL 组成。RL1 的表面活性更强，临界胶束浓度（CMC）值为 15mg/L，CMC 时的表面张力为 25mN/m。生物测定结果表明，RL1 是一种比 RL2 更有效的抗菌剂。所有耐甲氧西林金黄色葡萄球菌（MRSA）菌株均被 RLs 抑制，而与它们的抗生素敏感性模式无关。RLs 显著增强了 oxacillin 对 MRSA 菌株的活性，并将 oxacillin 的最低抑菌浓度降低至 3.12-6.25μg/mL 的范围。
