Original research paper Liquid chromatography–tandem mass spectrometry method for the quantification of a potent H 3 receptor antagonist conessine in serum and its application to pharmacokinetic studies Mahendra Shukla 1,2 , Femi M Francis 1,3 and Jawahar Lal 1,2 Abstract Conessine, a steroidal alkaloid obtained from the bark and seeds of the plant species of Apocynaceae family, elicits a histamine antagonistic action, selectively for the H 3 histaminergic receptors. This alkaloid is used mainly for the treatment of dysentery and helminthic disorders. For the quantification of conessine in serum, a liquid chromatography–tandem mass spectrometry method was developed. Chromatographic separation was achieved on a Zorbax SB-CN column (100  4.6 mm, 3.5 mm), and a mobile phase consisting of 90% methanol in aqueous ammonium acetate buffer (pH 3.5) with 0.1% (v/v) formic acid at an isocratic flow rate of 0.6 ml/min at 40  C provides efficiency in separation. A volume of 40 ml was injected each time and the run time for each sample was 5 min. Phenacetin (internal standard) was added to 50 ml of serum sample prior to liquid–liquid extraction using 3% isopropanol in n-hexane. The detection was performed on a 5500 QTRAP mass spectrometer by multiple reaction monitoring mode via electrospray ionization source. The multiple reaction monitoring of conessine and IS was m/z 357.4 to m/z 312.1 and m/z 180.1 to m/z 138.1, respectively. The method that showed selectivity and linearity in the range of 1–200 ng/ml was validated in terms of sensitivity, accuracy, precision and stability. The detection and quantitation limits were recognized at 0.1 and 1ng/ml, respectively. The intra- and inter-day precision and accuracy fulfils the acceptance criteria. Applying the method to the pharmacokinetic studies in rats, conessine showed a peak serum concentration at 2h post oral dose with a good bioavailability of 71.28  4.65%. Keywords Bioanalysis, histaminergic receptors, liquid chromatography–tandem mass spectrometry, multiple reaction monitoring, pharmacokinetics Received 20 June 2017; accepted 30 December 2017 Introduction Conessine is a steroidal alkaloid obtained from the bark and seeds of the plant species of Apocynaceae family, including Holarrhena floribunda, H. antidysen- terica and Funtumia elastica. 1 The stem bark is called ‘kurchi’ in the Indian subcontinent and is commonly known as ‘conessi bark’ in Europe. It elicits a hista- mine antagonistic action, selectively for the H 3 hista- minergic receptors. 2 Conessine (Figure 1) is also a potent substrate for adrenergic receptors and it is reported to have high blood–brain barrier permeabil- ity and long central nervous system clearance. 3 The alkaloid conessine is used mainly for the treatment of dysentery and helminthic disorders. It shows poten- tial amoebicidal action and many experiments were conducted to reveal out the same. 1,4 Recently, researchers reported that the plant H. antidysenterica possess activity against narcolepsy symptoms because of its natural content of conessine. However, several drugs affecting the H 3 receptor are now under 1 Pharmacokinetics & Metabolism Division, CSIR-Central Drug Research Institute, Lucknow, India 2 Academy of Scientific and Innovative Research, Mathura Road, New Delhi, India 3 Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Raebareli, India Corresponding author: Jawahar Lal, Pharmacokinetics & Metabolism Division, CSIR-Central Drug Research Institute, Jankipuram Extension, Sitapur Road, Lucknow 226031, India. Email: j_lal@cdri.res.in European Journal of Mass Spectrometry 0(00) 1–10 ! The Author(s) 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1469066718756226 journals.sagepub.com/home/ems