Background: Methoxyflavones are isolated from Kaempferia parviflora, a Thai herb used in
traditional medicine. The method of quantification of low level of methoxyflavones in biological samples
needs to be optimized.
Objectives: To develop and validate a sensitive liquid chromatography-tandem mass spectrometry (LC-MS)
for the determination of methoxyflavones in rat plasma and apply for pharmacokinetic study.
Method: Chromatographic separation was achieved on a reverse phase C18 column, using acetonitrile
and 0.5% formic acid in water in a ratio of 10:90 v/v to 50:50 v/v as the mobile phase, and a flow-rate of
0.2 ml/min at 25°C. LC–MS detection was performed under positive ionization with selective ion
monitoring using target ions.
Results: The calibration curve showed good linearity in the concentration range of 10–3000 ng/ml. The
limits of detection (LOD) and quantification (LOQ) were 0.43-0.78 ng/ml and 0.93-2.35 ng/ml,
respectively. The intra-day and the inter-day variances were less than 6.41% and 12.96%. The mean
recovery of methoxyflavones was 73.73- 99.76%. The assay was successfully applied to a
pharmacokinetics study in rats that used a topical application of 15% K. parviflora extract in IPM-based
vehicle. After topical administration, the plasma concentration of methoxyflavones continuously
increased up to 48 h, indicating prolonged absorption of methoxyflavones into systemic circulation, with
the maximum concentration (Cmax) of methoxyflavones being 401.94 ng/ml at 1 h.
Conclusion: The current method has been successfully applied to the determination of methoxyflavones
in rat plasma and was used to study its pharmacokinetics under topical administration.