Analysis of Volatile Compounds of Curcuma longa (Turmeric) and Investigation of the Antioxidant Activity of Rhizome Extracts

Abstract

Fragrances originating from plants are widely believed to have therapeutic properties. The volatile compounds originating from Curcuma longa (turmeric) plant cultivated in a medicinal plant garden located in southern Tokyo were investigated using thermal desorption-gas chromatography-mass spectrometry. Sampling from rhizomes of C. longa was performed at three different development stages, i.e., July (when young rhizomes emerge), September (flowers bloom), and November (ready for harvest). Using a polydimethylsiloxane (PDMS)-coated bar as an adsorption device for volatile compounds, 1,8-cineol, α-terpinolene, β-caryophyllene, and ar-curcumene were the predominant constituents in most cases. Additional volatile compounds such as α-terpinene, p-cymene, and (E)-β-farnesene were identified when PDMS/carboxene/divinylbenzene-coated fiber was used. ar-Turmerone was found from ripened rhizomes (in September and November). The leaves of C. longa yielded the same compounds as the rhizomes as well as compound characteristic of leaves such as 3-hexen-1-ol. The volatile compounds obtained from C. longa roots were the same as those from the rhizomes. The antioxidant activity of both water and methanol extracts of C. longa rhizomes collected from the medicinal plant garden was confirmed using electron spin-resonance spin-trapping method with potent scavenging activity against superoxide anion radical (O 2 ˑˉ). Extracts from ripe rhizomes ready for harvest exhibited greater antioxidant activity than those obtained from young rhizomes.