ABSTRACT
The antioxidant activities, total phenolics and total curcuminoid content of ethanolic extracts
of 8 species of Zingiber were determined using DPPH and ABTS assays compared with L-ascorbic
acid. The result showed that Zingiber officinalehad the highest antioxidant activities calculated in IC50
(the half maximal inhibitory concentration), 4.26 mg/ml and 7.04 mg/ml for DPPH assay and ABTS
assay, respectively. The total phenolics content was determined according to the Folin-Ciocalteu
method varied from 0.24-0.85 mgGAE/g of dry weight. The correlation between antioxidant activities
and total phenolics content was positive with correlation coefficient 0.777 (DPPH assay) and 0.817
(ABTS assay). Zingiber montanum showed the highest of total curcuminoids content, 2.63 %(w/w)
and the lowest was Zingiber ‘Plai chompoo’, 0.034 %(w/w). From this result, antioxidant activities were
positively correlated with the total phenolics content.