Antibacterial Compounds and Phytochemistry of Plants from the New England Tablelands (NSW) and the Genus Eremophila

Abstract

<p>Antibacterial resistance is increasing at a time when few new antibacterial compounds are being discovered. Many of the most important antibacterial agents that have been discovered to date are natural products. Plants are avid producers of natural products which they use, among other reasons, to defend against microbial invaders. To tap into these plant defences, this study relied upon a screening platform which included general antimicrobial assays, a new and robust thin layer chromatography with bioautography protocol, phytochemical profiling, compound isolation tools such as flash chromatography, and nuclear magnetic resonance spectroscopy for compound elucidation. The study revealed details of the phytochemistry and antibacterial potential of a number of plants, including <i>Olearia fulgens</i> and other species from the New England Tablelands of New South Wales, and several species from the genus <i>Eremophila</i>. More intensive work to uncover the antibacterial secondary metabolites of plants with bioactive extracts resulted in the discovery of previously undescribed compounds including a labdane glycoside, a serrulatic acid and clerodanes. The activity of isolated antibacterial compounds in this work supports a view that many plants generally produce poorly or moderately active secondary metabolites rather than compounds which are highly active. An additional output of the study was the creation of an extensive online phytochemical database of <i>Eremophila</i>. This tool was created to avoid rediscovering known compounds and to indicate which species had poorly describable phytochemical profiles and were thus worthy of further investigation. It is hoped that this database can now benefit other researchers in fields as diverse as ethnobotany, chemistry and taxonomy.</p>