ABSTRACT
This chapter focuses on 'essential oils' and aromas from plant species that have a potential to influence cognition and mood, and discusses the evidence and challenges for the scientific basis for their use for such therapeutic applications. Essential oils consist of highly complex mixtures of phytochemicals and the main components are terpenoids, monoterpenoids, sesquiterpenoids and phenylpropanoids, which may occur as hydrocarbons or oxygenated derivatives. The chemistry and polarity of the oil constituents may be important when considering factors such as their bioavailability and their ability to cross the blood–brain barrier, to mediate effects in the central nervous system relevant to mood and cognitive functions. The low molecular weight volatile constituents that occur in essential oils are widely used in the practice of aromatherapy and are often inhaled to mediate their reputed effects. The pharmacological benefits emanate from the ability of their whole extracts or constituents therein, perhaps synergistically, to interact with enzymes or receptors that influence cognitive and mood outcomes.
