This study was designed to examine the in vitro antioxidant activities of the essential oil and methanol extracts of rhizoma Alpinia officinarum (small galanga) from China. The essential oil was analyzed by gas chromatography/ mass spectrometry (GC/MS) and 46 constituents were identified. Methanol extract from rhizoma A. officinarum was fractionated by chromatography of silica gel using ethyl acetate, acetone-methanol (8:1, V/V) and methanol, respectively. The antioxidant activities of essential oil and methanol extracts were evaluated with reducing power, diphenylpicrylhydrazyl (DPPH) assay and ferric thiocyanate test. In the above three assays, the essential oil and methanol extracts showed antioxidant potential to varying degrees; and acetone-methanol (8:1, V/V) subfraction exhibited better antioxidant potency than others. Owing to having antioxidative components, the essential oil exhibited satisfying antioxidant activities. A positive correlation was observed between the antioxidant activity potential and total phenolic contents of the extracts.
Key words: Rhizoma Alpinia officinarum, antioxidant activity, essential oil, methanol extracts, gas chromatography-mass spectrometry.
BHA, Butylated hydroxyanisole; BHT, butylated hydroxytoluene; TBHQ, tert-butylhydroquinone; GC/MS, gas chromatography-mass spectrometry;TCA, trichloroacetic acid; DPPH, 1, 1-diphenyl-2-picrylhydrazyl; FCR, folin-ciocalteu reagent; GAE, gallic acid equivalents.
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