CHEMICAL CONSTITUENTS AND IN VITRO ANTIOXIDANT ACTIVITIES OF ESSENTIAL OIL FROM CURCUMA LEUCORRHIZA ROXB. RHIZOME

Abstract

The hydrodistillate essential oil from the fresh rhizomes of Curcuma leucorrhiza Roxb. was investigated for chemical constituents by gas chromatography-mass spectroscopy (GC-MS) and antioxidant activities by five different methods including DPPH radical scavenging, hydroxyl radical scavenging, hydrogen peroxide scavenging, ferrous ion chelating and ferric reducing power assays.  L-ascorbic acid and ethylenediaminetetraacetic acid (EDTA) were used as a positive control. The three major components in the essential oil were found to be germacrene D (21.65%), selina-3, 7(11)-diene (16.67%) and α-longinipine (11.16%). The EC₅₀ value of the essential oil against hydroxyl radicals (10.72 ± 1.54 μg/ml) was found to be significantly higher than that of L-ascorbic acid (18.27 ± 1.54 μg/ml). The DPPH radical scavenging activity, hydrogen peroxide scavenging activity and ferric reducing power of the essential oil and L-ascorbic acid were found to be insignificantly different. The EC₅₀ values of the essential oil and L-ascorbic acid were 8.88 ± 0.74 and 10.77 ± 0.97 μg/ml, respectively, for DPPH radical scavenging activity, 12.88 ± 1.38 and 11.04 ± 1.03 μg/ml, respectively, for hydrogen peroxide scavenging activity and 0.14 ± 0.02 and 0.10 ± 0.02 μg/ml, respectively, for ferric reducing power.  The essential oil showed less ferrous ion chelating activity with its EC₅₀ value of 345.62 ± 13.29 μg/ml as compared with EDTA with its EC₅₀ value of 154.19 ± 2.45 μg/ml.