In vitro cytochrome P450 activity: development and validation of a sensitive high performance liquid chromatography-tandem mass spectrometry method for the quantification of six probe metabolites after derivatization with pyridine-3-sulfonyl chloride in an aqueous environment.

For the determination of the in vitro cytochrome P450 activity in microsomes, a quantification method for the probe metabolites, formed during incubation, is required. Due to insufficient sensitivity of a previously developed high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for some of the metabolites, a fast and easy derivatization method with pyridine-3-sulfonyl chloride (PS) is described. Acetaminophen (CYP1A2), dextrorphan (CYP2D6), hydroxy-chlorzoxazone (CYP2E1) and hydroxy-mephenytoin (CYP2C19) can be derivatized because of the presence of a phenolic OH, whereas hydroxy-midazolam (CYP3A4) and hydroxy-tolbutamide (CYP2C9) remain unchanged.

Dissection of the phytohormonal regulation of trichome formation and biosynthesis of the antimalarial compound artemisinin in Artemisia annua plants.

• Biosynthesis of the sesquiterpene lactone and potent antimalarial drug artemisinin occurs in glandular trichomes of Artemisia annua plants and is subjected to a strict network of developmental and other regulatory cues. • The effects of three hormones, jasmonate, gibberellin and cytokinin, were studied at the structural and molecular levels in two different A. annua chemotypes by microscopic analysis of gland development, and by targeted metabolite and transcript profiling.

Quantitation of artemisinin and its biosynthetic precursors in Artemisia annua L. by high performance liquid chromatography-electrospray quadrupole time-of-flight tandem mass spectrometry.

This study reports the development and validation of a rapid, sensitive and selective assay for the quantitation of artemisinin, arteannuin B, artemisitene and artemisinic acid in Artemisia annua L. by reversed phase high performance liquid chromatography (HPLC) electrospray (ESI) quadrupole time of flight (Q-TOF) tandem mass spectrometry (MS/MS). A recovery of >97% for all analytes was achieved by immersing one gram of fresh plant material in chloroform for 1 min.