Orczyk Marta, Wojciechowski Kamil
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
Colloids Surf B Biointerfaces. 2015 Dec 1;136:291-9. doi: 10.1016/j.colsurfb.2015.09.018. Epub 2015 Sep 12.
The present study aims at comparing the effect of two commercially available Quillaja bark saponin (QBS) products on model Langmuir monolayers. Pure dipalmitoylphosphatidylcholine (DPPC) and mixed DPPC/cholesterol Langmuir monolayers were used as crude models of erythrocyte membranes in order to better understand a hemolytic activity of QBS. Both QBS products are mixtures of several saponins and non-saponin fractions, only few of which can be assigned an exact chemical structure, as shown by an HPLC analysis. Noticeable differences in the saponin profiles, and most importantly-in the content of non-saponin fractions (tannins and phenolic compounds) are probably responsible for their different adsorption behavior at the water/air interface. The lipids Langmuir monolayers were initially spread on pure water and compressed to surface pressure of 32.5 mN/m, which is believed to provide the lipid packing similar to that in real biological membranes. The water subphase was subsequently exchanged with the respective QBS solutions in the concentration range 5 × 10(-4) to 2 × 10(-1)wt%. In order to assess the resistance of the model lipid monolayers to QBS, a combination of surface pressure relaxation and surface dilatational rheology was employed. Both QBS are shown to penetrate the lipid layers without removing them, but their effect on the lipid layers' relaxation and viscoelastic dilational properties is different. The differences virtually disappear when cholesterol is present in the monolayer, especially for the DPPC/Cholesterol molar ratio between 10:9 and 4:1 (mol/mol). Despite several jumps of surface pressure, the lipid layers containing cholesterol can resist penetration of QBS.
本研究旨在比较两种市售的皂树树皮皂苷（QBS）产品对模型朗缪尔单分子层的影响。使用纯二棕榈酰磷脂酰胆碱（DPPC）和混合的DPPC/胆固醇朗缪尔单分子层作为红细胞膜的粗模型，以便更好地理解QBS的溶血活性。如HPLC分析所示，两种QBS产品均为几种皂苷和非皂苷组分的混合物，其中只有少数能够确定其确切的化学结构。皂苷谱的显著差异，最重要的是——非皂苷组分（单宁和酚类化合物）含量的差异，可能是它们在水/空气界面具有不同吸附行为的原因。脂质朗缪尔单分子层最初铺展在纯水上，并压缩至32.5 mN/m的表面压力，据信这能提供与真实生物膜中相似的脂质堆积。随后将水亚相换成浓度范围为5×10⁻⁴至2×10⁻¹ wt%的相应QBS溶液。为了评估模型脂质单分子层对QBS的抗性，采用了表面压力松弛和表面膨胀流变学相结合的方法。结果表明，两种QBS均能穿透脂质层而不将其去除，但它们对脂质层松弛和粘弹性膨胀特性的影响不同。当单分子层中存在胆固醇时，尤其是DPPC/胆固醇摩尔比在10:9至4:1（mol/mol）之间时，这些差异实际上消失了。尽管表面压力有几次跃升，但含有胆固醇的脂质层能够抵抗QBS的穿透。
