Comparison of chemical composition and antioxidant potential of volatile oil from fresh, dried and cured turmeric (Curcuma longa) rhizomes

The present work was conducted to assess and compare the chemical composition of volatile oils from fresh, dried and cured turmeric (Curcuma longa) rhizomes from a selected single source. In addition, their antioxidant and radical scavenging potentials were correlated with chemical composition. Major components were ar-turmerone (21.0–30.3%),
α-turmerone (26.5–33.5%) and β-turmerone (18.9–21.1%). Trolox equivalent antioxidant capacity (TEAC) values were 38.9, 68.0 and 66.9 μM at 1 mg of oil/ml for fresh, dried and cured rhizome respectively in ABTS assay. IC50 values for fresh, dried and cured rhizome oil to quench DPPH radicals were 4.4, 3.5 and 3.9 mg of oil/ml respectively. Fresh, dried and cured rhizome oils showed antioxidant capacity of 358, 686 and 638 mM of ascorbic acid equivalents per 1 mg of oil respectively. The rhizome oil shows good reducing potential and was concentration dependent. It is inferred that the cured rhizomes provided high yield of volatile oil with appreciably high antioxidant potential.