Therapeutic Properties of Bioactive Secondary Metabolites in Essential Oil Crops

Medicinal herbs and their essential oils (EOs) are of commercial and industrial importance with diverse uses as forage and fiber crops, in food, cosmetics, perfumery and chemical industries, and in traditional medicine due to their phytochemical constituents and bioactivities. This chapter was aimed at documenting the therapeutic properties of major secondary metabolites in EOs extracted from six selected economically important medicinal herbs (Achillea millefolium L., Melissa officinalis L., Origanum majorana L., Pelargonium graveolens L'Hér. Rosmarinus officinalis L. and Thymus vulgaris L.). Forty-five compounds (mainly monoterpenes) were recorded as major compounds of the six medicinal herbs. The compounds possess varying biological activities, which include antimicrobial, anti-inflammatory, antioxidant and cytotoxicity properties. Other activities reported were antinociceptive, neuroprotective effects, acetylcholinesterase inhibition, anti-ulcerogenic, DNA protection, glutathione S-transferase activity, chemoprotective, anti-depressant and sedative effects. The compounds showed potential to be used as alternative agents as drugs, cosmetic ingredients and food additives. Though some scientific evidence has confirmed the use of these herbs in various industries, much work still needs to be done to comprehend the therapeutic application of their EOs and phytoconstituents to benefit from their full potential.