ABSTRACT
The preservative properties of aromatic and medicinal plant volatile [essential] oils and extracts have been recognised since Biblical times, while attempts to characterise these properties in the laboratory date back to the 1900s (Martindale, 1910; Hoffman and Evans, 1911). Plant volatile oils are generally isolated from non-woody plant material by steam or hydrodistillation, and are variable mixtures of principally terpenoids, specifically monoterpenes [C10] and sesquiterpenes [C15] although diterpenes [C20] may also be present, and a variety of low molecular weight aliphatic hydrocarbons [linear, ramified, saturated and unsaturated], acids, alcohols, aldehydes, acyclic esters or lactones and exceptionally nitrogen-and sulphur-containing compounds, coumarins and homologues of phenylpropanoids.
