Biological Activities of Essential Oils: From Plant Chemoecology to Traditional Healing Systems

Abstract

Essential oils are complex mixtures of hydrocarbons and their oxygenated derivatives arising from two different isoprenoid pathways. Essential oils are produced by glandular trichomes and other secretory structures, specialized secretory tissues mainly diffused onto the surface of plant organs, particularly flowers and leaves, thus exerting a pivotal ecological role in plant. In addition, essential oils have been used, since ancient times, in many different traditional healing systems all over the world, because of their biological activities. Many preclinical studies have documented antimicrobial, antioxidant, anti-inflammatory and anticancer activities of essential oils in a number of cell and animal models, also elucidating their mechanism of action and pharmacological targets, though the paucity of in human studies limits the potential of essential oils as effective and safe phytotherapeutic agents. More well-designed clinical trials are needed in order to ascertain the real efficacy and safety of these plant products.

Keywords: antimicrobial activity; ethnobotany; isoprenoids; monoterpenes; oral healthcare; traditional healing systems.

Figure 1

Isoprenoid biosynthetic routes in plant cell: mevalonic pathway, in cytoplasm, and 2-C-methyl-d-erythritol-4-phosphate in plastids; isoprenoids synthesis from precursors (isopentenyl pyrophosphate and dimethylallyl pyrophosphate) occurs in cytoplasm.

Figure 2

Biogenic volatile compounds produced by plants include monoterpene and sesquiterpene hydrocarbons, as well as oxygenated monoterpenes and sesquiterpenes, also referred to terpenes and terpenoids, respectively; these compounds are the main constituents of essential oils.