title: Grazing incidence diffraction studies of the interactions between ursane-type antimicrobial triterpenes and bacterial anionic phospholipids.
abstract: α-Amyrin (AMalf) and ursolic acid (Urs) are ursane-type pentacyclic triterpenes which exhibit wide spectrum of antibacterial activity. These surface active compounds can be incorporated into bacterial membranes and alter their structure and function; however, the exact mechanism of their action still needs to be elucidated. Thus, we decided to study the interactions of these terpenes with specific anionic phospholipids:cardiolipins and phosphatidylglycerols extracted from Escherichia coli in the model environment of Langmuir monolayers. To characterize the ordering of the terpene molecules in one-component films as well as to study their interactions with the bacterial phospholipids in binary monolayers we applied grazing incidence X-ray diffraction (GIXD). It turned out that amyrins and ursolic acid molecules form crystalline hexagonal phases in Langmuir monolayers, in which the molecules are oriented uprightly. Regarding the mixtures, it was found that in the monolayers with Urs crystalline domains are present till moderate or even low Urs proportion. In contrast, in the mixtures with AMalf crystalline domains were observed only at the highest terpene concentration. In the interpretation of our results we underlined the significance of the interactions between the cyclopropane ring present in the hydrophobic part of the bacterial phospholipids and the terminal ring of the terpene structure. We proposed that the significant differences between the systems with AMalf and Urs are connected with the formation of hydrogen bonds between the Urs hydrophobic moieties. It can be inferred from the results that Urs is a more membrane-active agent than AMalf.
authors: Department of Environmental Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 3, 30-387 Krakow, Poland. Electronic address: broniato@chemia.uj.edu.pl.
authors: Marcin
authors: M
authors: Broniatowski
authors: Department of Environmental Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 3, 30-387 Krakow, Poland.
authors: Michał
authors: M
authors: Flasiński
authors: Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland.
authors: Paweł
authors: P
authors: Wydro
authors: Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin, BP48, 91192 Gif sur Yvette Cedex, France.
authors: Philippe
authors: P
authors: Fontaine
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry*; D002308:Cardiolipins / Q000737:chemistry* / Q000302:isolation & purification; D003460:Crystallization; D004926:Escherichia coli / Q000737:chemistry; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry* / Q000302:isolation & purification; D013816:Thermodynamics; D014315:Triterpenes / Q000737:chemistry*; D000097245:Ursolic Acid
chemical_list: D000890:Anti-Infective Agents; D002308:Cardiolipins; D008567:Membranes, Artificial; D009828:Oleanolic Acid; D010715:Phosphatidylglycerols; D014315:Triterpenes; D000097245:Ursolic Acid; C036380:beta-amyrin
keywords: Bacterial membranes; Grazing incidence X-ray diffraction; Langmuir monolayers; Pentacyclic triterpenes