Physical properties and antimicrobial activities of leaf essential oil of Lippia multiflora Moldenke

This study was designed to investigate the physical properties and antimicrobial activities of the essential oil hydrodistilled from leaves of Lippia multiflora (lippia oil) in order to develop the oil to a pharmaceutical standard. The values of the physical parameters of the oil were weight-per-millilitre: 0.8762 ± 0.0041 g, refractive index: 1.468 ± 0.001, optical rotation range: from +46.55° to +57.60°, residue on evaporation: 3.85 ± 0.96%, pH: 4.75 ± 0.24, kinematic viscosity: 5.46 ± 0.02 cSt and surface tension: 29.20 ± 0.04 dyn/cm at 28 °C. Lippia oil was soluble in 1 volume of ethanol (80%) at 28 °C, with the solution becoming opalescence on addition of 4 or more volumes of the ethanol. The oil is highly volatile at temperatures above 37.7 °C. While fungi were more susceptible to the lippia oil than bacteria, the oil was found to be more effective against Gram-positive bacteria than Gram-negative bacteria, with clinical isolates showing more resistance than type strains. The potential application of the physical properties and antimicrobial activities of lippia oil in its formulation as a drug product is discussed.