Antioxidant Activities and Chemical Composition of Essential Oil of Rhizomes of Zingiber officinale (Ginger) and Curcuma longa L.(Turmeric)

Abstract

This study aimed to determine the essential oil volatile components of ginger and turmeric rhizomes, as well as to determine the total antioxidant capacity of essential oil samples according to the CUPric Reducing Antioxidant Capacity (CUPRAC), ferric reducing antioxidant potential (FRAP) method and free radical scavenging activities of oil samples and standards such as BHA, BHT, and Trolox were determined using a DPPH method. Essential oil analysis of volatile components was also performed on a Shimadzu GCMS-QP2010 SE (Japan) model with Support Rx-5Sil MS capillary column (30 m x 0.25 mm, film thickness 0.25 μm). Antioxidant capacities of essential oils were evaluated according to the CUPRAC method in millimole Trolox/gram -oil equivalent. GC-MS analysis of ginger showed the presence of 5 major peaks identified as Curcumene (13.46%), Zingiberene (33.92%), α-Farnesene (8.07%), β-Bisabolene (6.39%), and β-Sesquiphellandrene (15.92 %), respectively. GC-MS analysis of Turmeric showed the presence of 3 major peaks identified as Ar-Turmerone (29.24%), α-Turmerone (22.8 %), and β-Turmerone (18.84%). CUPRAC values of calculated antioxidant capacities of essential oil samples were determined as 1.97 ± 0.102 mmolTR/g-oil for Zingiber officinale R. and 3.40 ± 0.071 mmol TR/g-oil for Curcuma longa L. The scavenging effect of turmeric, ginger and standards on the DPPH radical decreased in the order of Trolox>BHA>BHT>Turmeric>Ginger which were 95.25 ± 0.05%, 62.57 ± 0.34%, 61.6 ± 0.3%, 51.45 ± 0.59%, and 50.26 ± 0.09%, at the concentration of 150µg/mL, respectively. Additionally, it revealed that essential oils of turmeric and ginger exhibited effective ferric reducing power.