Antioxidant activity of essential oils and oleoresing from turmeric roots (Curcuma Longa L.) extracted with different solvents and its correlation to the curcuminoid content

Abstract

The purpose of present investigation was to evaluate the potential antioxidant activity and total curcuminoid content of essential oils and oleoresins extracted from turmeric roots (Curcuma Longa L.). Water distillation method was used to obtain essential oil from fresh and dried turmeric. Otherwise, oleoresins were extracted from dried turmeric with different solvents by using Soxhlet extraction. The essential oil content was 1.00 v/w% in fresh turmeric and 3.83 v/w% in dried turmeric. The oleoresin extraction yields were 4.06%, 14.44%, 16.31% and 18.54% corresponding to hexane, ethyl acetate, ethanol and methanol extracts. Total curcuminoid content was quantified by using spectrophotometric method. The curcuminoid content in the oleoresin extracted with ethyl acetate was highest (46.27%), meanwhile the curcuminoid content of ethanol extract, methanol extract and hexane extract were 39.53%, 37.00% and 7.50%, respectively. In contrast, the essential oils had extremely low curcuminoid content which was near zero. Antioxidant activity of the essential oils and oleoresins was investigated based on their ability to scavenge stable free radical (DPPH). The EC50 value of the oleoresins ranged between 5.03 and 119.74 µg/ml and that of ascorbic acid was 7.51µg/ml. However, the essential oils showed weaker antioxidant ability than the oleoresins, with undefined EC50 value. In general, the result showed a significant correlation between antioxidant activity and total curcuminoid content in all the oleoresin samples.

Keywords: Antioxidant activity Curcuminoids Curcuma Longa L. DPPH