Langmuir monolayers were used as a model system to investigate the antimicrobial properties of tea tree oil. Tea Tree oil is an essential oil that comes from the leaves of the Australian tea tree. It is used to treat common ailments such as acne, nail fungus and insect bites. Recent studies have shown that tea tree oil’s major constituent, terpinen-4-ol, has anti-inflammatory properties by increasing the activity of white blood cells. Tea tree oil has also been shown to have cytotoxic properties when applied topically. Langmuir monolayers allow for the molecular area of cellular membrane lipids and surface active molecules to be measured as a function of pressure at an air-water interface. In this research, we utilized monolayers of common phospholipids, dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE), dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE), to determine how the compounds in tea tree oil break down cell membranes. Results indicate that PE headgroups in DPPE monolayers are disrupted by the tea tree oil to a greater extent than PC headgroups which is surprising due to the PE-PE hydrogen bonding capability in these monolayers. The oil was shown to fluidize monolayers of unsaturated lipids more than saturated ones as seen by a lower collapse pressure of the film. Terpinen-4-ol was found to affect the organization of saturated phospholipids to a greater extent than unsaturated ones. These initial studies indicate that the tea tree oil/phospholipid interactions are both headgroup and tailgroup mediated. For a more physiological model of a cell, we are also using <i>E.coli</i> lipid extract as our model system. In future studies, we plan to utilize Langmuir monolayers to investigate the cytotoxic properties of tea tree oil by modeling cancer cells.

Investigating the surface molecular interactions of tea tree oil and phospholipids via Langmuir monolayers

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