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There are >80 species of turmeric (Curcuma spp.) and some species have multiple varieties, for example, Curcuma longa (C. longa) has 70 varieties. They could be different in their chemical properties and biological activities. Therefore, we compared antioxidant activity, total phenolic and flavonoid content of different species and varieties of turmeric namely C. longa [variety: Ryudai gold (RD) and Okinawa ukon], C. xanthorrhiza, C. aromatica, C. amada, and C. zedoaria. The antioxidant activity was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, oxygen radical absorbance capacity (ORAC), reducing power and 2-deoxyribose (2-DR) oxidation assay. Our results suggested that RD contained significantly higher concentrations of total phenolic (157.4 mg gallic acid equivalent/g extract) and flavonoids (1089.5 mg rutin equivalent/g extract). RD also showed significantly higher DPPH radical-scavenging activity (IC 50 : 26.4 μg/mL), ORAC (14,090 μmol Trolox equivalent/g extract), reducing power absorbance (0.33) and hydroxyl radical scavenging activity (IC 50 : 7.4 μg/mL). Therefore, RD was chosen for the isolation of antioxidant compounds using silica gel column, Toyopearl HW-40F column, and high-performance liquid chromatography. Structural identification of the compounds was conducted using 1 H NMR, 13 C NMR, and liquid chromatography-tandem mass spectrometry. The purified antioxidant compounds were bisabolone-9-one (1), 4-methyllene-5-hydroxybisabola-2,10-diene-9-one (2), turmeronol B (3), 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-1-hepten-3-one (4), 3-hydroxy-1,7-bis(4-hydroxyphenyl)-6-hepten-1,5-dione (5), cyclobisdemethoxycurcumin (6), bisdemethoxycurcumin (7), demethoxycurcumin (8) and curcumin (9). The IC 50 for DPPH radical-scavenging activity were 474, 621, 234, 29, 39, 257, 198, 47 and 18 μM and hydroxyl radical-scavenging activity were 25.1, 24.4, 20.2, 2.1, 5.1, 17.2, 7.2, 3.3 and 1.5 μM for compound 1, 2, 3, 4, 5, 6, 7, 8 and 9, respectively. Our findings suggested that the RD variety of C. longa, developed by the University of the Ryukyus, Okinawa, Japan, is a promising source of natural antioxidants., (Copyright © 2018 Elsevier Inc. All rights reserved.)

To clarify the characteristics of genus Curcuma plants, we studied the properties of six strains of Curcuma longa L. and two strains of C. aromatica Salisb. preserved at Izu Experimental Station for Medicinal Plants of National Institute of Health Sciences. Six strains of C. longa were classified into three types according to morphological characteristics, rhizome production, and differences in curcuminoid content of rhizome. The curcuminoid content of the rhizomes in each strain ranged from 2.20 mg/g to 55.23 mg/g. Strains showing a high curcuminoid content had a low rhizome yield. No difference was observed between two strains of C. aromatica in terms of morphological characteristics. C. longa can be easily distinguished by differences in the development of tuberous roots and the color of the rhizome cross section.