Development and application of a gas chromatographic/mass spectrometric/mass spectrometric method for the determination of 5-methoxyflavone in rat and dog plasma

A gas chromatographic/mass spectrometric/mass spectrometric method was developed for the determination of 5‐methoxyflavone in plasma. Optimized detection schemes for 5‐methoxyflavone readily allow a limit of quantification of 1 ng ml−1 in rat or dog plasma (1.0 ml sample volume). The complete analysis time (injection to injection) is less than 9 min and allows for rapid automated sample throughput. Additional advantages include a high degree of specifity and good accuracy and precision. This type of rapid tandem mass spectrometric assay has been found to be particularly useful in pharmaceutical discovery, since an assay for one compound can be quickly developed, utilized and then modified to determine analogs of similar structure. Application of this methodology to pilot preclinical pharmacokinetic studies of the drug indicated that it is rapidly absorbed and cleared, with an apparent terminal half‐life of about 15 min in dogs. Bioavailability in the two dogs tested ranged 33 to 72%, but was about 25% in rats.