Cyclic Voltammetry and Spectrophotometric Determination of Antioxidant Activities of Selected Ginger Species

Introduction: Zingiberaceae rhizomes are commonly investigated due to its applications in food and traditional medicine use. However, less scientific attention was given to its leaves. Aim: This study primarily aimed to compare the antioxidant activity of the leaves and rhizomes of common Zingiberaceae plants namely: Zingiber officinale, Curcuma longa and Etlingera elatior. Methods: Antioxidant activity of the water and ethanol extracts of the leaves and rhizomes of the studied plants was determined using cyclic voltammetry (CV) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Results: Very low positive correlation (r = 0.22) of antioxidant activities was observed between DPPH and CV methods. In both DPPH and CV methods, E. elatior has generally higher antioxidant activity in leaves than in rhizomes and water extract than ethanol extracts. Higher antioxidant activity was observed in leaves than in rhizomes for Z. officinale and C. longa for both water and ethanol extracts. In general, water extracts of the three ginger plants have higher antioxidant activity than its ethanol extracts. Conclusion: Both CV and DPPH assay revealed that leaves of common gingers studied are potential sources of antioxidants.