Effects of extraction methods on antioxidants and methoxyflavones of Kaempferia parviflora

This research was aimed to determine the effects of extraction methods on antioxidant properties and methoxyflavone contents of Kaempferia parviflora (KP) rhizome extracts. The KP rhizomes were extracted by maceration using ethanol at the concentrations of 25, 50, 75 and 95% V/V for 7 days and 95% V/V ethanolic extraction with sonication-assisted extraction (SAE) for 15-45 mins. Antioxidant components (phenolics, flavonoids and anthocyanins) and antioxidant activities (DPPH and FRAP) were examined. Methoxyflavones of the KP extracts were identified by a GC-MS technique. It was found that extraction methods affected the antioxidant properties of the extracts. Increasing ethanol concentrations enhanced anthocyanins but not phenolics and flavonoids. Ethanol concentration at 75% V/V exhibited the greatest DPPH while 25% V/V ethanol showed the greatest FRAP values. In this study, 10 methoxyflavones from KP extracts were separated and identified by GC chromatograms. The content of 5,7-dimethoxyflavone increased from 1.1 g/100 mL extract to 48.10 g/100 mL extract as the ethanol concentrations increased from 25% to 95% V/V. SAE for 15-45 mins had little impact on antioxidant properties as well as methoxyflavone contents. In general, SAE enhanced the extraction of KP rhizomes by increasing 5,7-dimethoxyflavone contents.