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.