Ginger essential oil: Chemical composition, extraction, characterization, pharmacological activities, and applications

Ginger (Zingiber officinale Roscoe) belongs to the Zingiberaceae plant family. It is cultivated in subtropical and tropical countries and has been used commonly as a spice and home remedy for many centuries. Ginger constituents, especially essential oils (GEO), have recently gained popularity due to their antioxidant, anticancer, antimicrobial, and anti-ulcer effects. The essential oil extracted from ginger rhizome has also been commercially recognized across the globe and used in the pharmaceutical and food industries. GEO typically contains (95%–99%) volatile constituents with (1%–4%) oil yield from dry ginger, and α-zingiberene is the significant component; however, the GEO's chemical composition and yield are affected geographical origin, cultivars, harvesting time, drying method, and extraction techniques. This chapter describes the effect of different factors on GEO yield and chemical composition and briefly discusses the widely used analytical method to characterize the GEO. The conventional extraction method (hydro-distillation, steam distillation, solvent extraction/liquid–liquid, Soxhlet) and advanced method of extraction (Supercritical CO2, Subcritical water, Solvent-free, Microwave-assisted, and Microwave hydro-diffusion and gravity) have been described. Furthermore, applications of GEO in the pharmaceutical and food industries are discussed. The regulations pertaining to GEO safety, toxicity, transport, and storage standards have also been briefly reviewed in this chapter.