Bioactivity of Essential Oils and Their Components

Institute Multidisciplinario de Biologia Vegetal (IMBIV-CONICET), National University of Cordoba. Argentina 

Essential oils (EOs) are secondary metabolites that plants usually synthesized for combating infectious or parasitic agents or generate in response to stress conditions [1]. EOs are aromatic components obtained from different plant parts such as flower, buds, seed, leaves and fruits, and they have been employed for a long time in different industries, mainly in perfumes (fragrances and aftershaves), in food (as flavouring and preservatives) and in pharmaceuticals (therapeutic action) [2]. 

The commercialization of EOs can be targeted around their bioactivity, and in this context the discovery of new uses and applications of EOs will further drive the research and development process [5]. EOs with promising activities are thus reviewed in the present work. 

In the last few years, there has been target interest in biologically active compounds, isolated from plant species for the elimination of pathogenic microorganisms, because of the resistance that microorganisms have built against antibiotics [6] or because they are ecologically safe compounds [7]. 

A wide variety of EOs are known to possess antimicrobial properties and in many cases this activity is due to the presence of active constituents, mainly attributable to isoprenes such as monoterpenes, sesquiterpenes and related alcohols, other hydrocarbons and phenols [8, 9]. 

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Koroch AR, Juliani HR, Zygaldo JA (2007) Bioactivity of essential oils and their components. In Berger RG (ed) Flavours and fragrances. Chemistry, bioprocessing and sustainability. Springer, Berlin... 

In nature, essential oils having aroma and flavor are isolated from the various parts of the plants [39]. The essential oils for commercial utiUzation can be isolated using various methodologies which include steam distillation, solvent extraction, and expression [39, 44]. As reported previously, most of the plant essential oils exert potent biological efficacy [11, 35, 39, 45 7]. The antimicrobial or other biological activities of essential oils are directly correlated to the presence of their bioactive volatile components [11, 43, 48]. 

To ensure lot-to-lot consistency, standardization of extracts often relies on constituents as biomarkers for plant identity and potency. SJW Hypericum perforatum), a perennial shrub traditionally used as a mood enhancer and mild antidepressant, has been tested in dozens of clinical trials, with mixed results for efficacy. Some of its purported bioactive constituents include naphthodianthrones, including hypericin flavonoids phloroglucinols, including hyperforin and essential oils. For many years, hypericin was presumed to be the active component. As a result most extracts were standardized based on hypericin concentration. Recent data, however, support other components such as hyperforin and the flavanoids, that may also contribute to the therapeutic efficacy of the SJW extracts (33-35). Because these secondary components were previously unaccounted for in the standardization of the former clinical test articles, and because these constituents are chemically unrelated to and their content within the plant varies independently of hypericin, it has been argued that the potency of these constituents in any particular batch was unlikely to be similar to that of other batches. This variability between batches could explain the observed differences in the clinical trial results (36). 

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