Analysis of Compounds of Curcuma Rhizome Using Mass Spectrometry and Investigation of the Antioxidant Activity of Rhizome Extracts

The medicinal plant garden of Hoshi University located in southern Tokyo is home to many medicinal plants, and analysis of odor and measurement of antioxidant activity of cultivated plant have been carried out. In this study compounds originated from Curcuma rhizomes, i.e., Curcuma longa, Curcuma aromatica, Curcuma zedoaria, Curcuma xanthorrhiza, were investigated and antioxidant activities of rhizome extracts were measured. Volatile compounds originating from the Curcuma rhizomes were analyzed using thermal desorption (TD)-GC-MS with solid-phase micro extraction fiber as an adsorption device. p-Cymene, 1,8-cineol, β-elemene, and β-caryophyllene were the predominant constituents in most cases. Curcuminoids, which were not identified by TD-GC-MS, were detected using direct analysis in real time time-of-flight MS. Curcumin and demethoxycurcumin were detected from both C. longa and C. xanthorrhiza. The antioxidant activity of each Curcuma species rhizome was confirmed using the electron spin-resonance spin-trapping method with potent scavenging activity against superoxide anion radicals. Extracts from Curcuma rhizomes cultivated in the medicinal plant garden exhibited antioxidant activities, and the order of the activity of methanol extracts was: C. longa>C. xanthorrhiza>C. aromatica>C. zedoaria. Phenolic compounds, particularly curcumin, are known to possess potent antioxidant activity and are extracted with methanol, thus it reflects the intensity of the antioxidant activity.