Send Orders for Reprints to reprints@benthamscience.net Current Chromatography, 2014, 1, 41-51 41 Recent Advances on Liquid Chromatographic and Mass Spectrometric Analysis of Selective Estrogen Receptor Modulators (SERMs) in Biological Fluids Konstantinos M. Kasiotis 1, *, Evangelia N. Tzanetou 2 and Serkos A. Haroutounian 2 1 Benaki Phytopathological Institute, Laboratory of Pesticides Toxicology, 8 St. Delta Street, Athens, Kifissia 14561, Greece; 2 Chemistry Laboratory, Agricultural University of Athens, Iera odos 75, Athens 11855, Greece Abstract: Selective Estrogen Receptor Modulators (SERMs) comprise a class of therapeutic agents widely prescribed for the prevention and treatment of breast cancer, osteoporosis and postmenopausal symptoms. SERMs are exemplified by Tamoxifen (TAM), a molecule displaying pronounced activity that is mediated through its in vivo active metabolites (Z)- 4-hydroxytamoxifen and endoxifen. The extensive in vivo metabolism of SERMs along with their wide use as medica- tions, has led to the development of specific methods for the efficient separation and accurate identification of their parent molecules and metabolites in biological fluids. For this purpose, Liquid Chromatography (LC) is considered the most effi- cient separation technique, especially when combined with mass spectrometry in simple (LC-MS) and/or tandem mode (LC-MS/MS), constituting the cutting edge analytical approach in terms of selectivity and sensitivity. This review intends to account the major recent advances on the LC-MS determination of SERMs and metabolites in biological fluids, a sub- ject not reviewed to date with the exception of TAM which was extensively reviewed on 2010, consequencing the inclu- sion of only very recent reports on TAM assessments. Keywords: Bioanalysis, biological fluids, endoxifen, extraction, HPLC, LC-MS, LC-MS/MS, mass spectrometry, metabolites, MRM transitions, precipitation, raloxifene, SERMs, solid phase, tamoxifen. INTRODUCTION Selective Estrogen Receptor Modulators (SERMs) en- compass a class of therapeutic agents extensively prescribed for the prevention and treatment of breast cancer, osteoporo- sis and postmenopausal symptoms. Tamoxifen (TAM) (Fig. 1) constitutes the prototype of first generation SERMs, which is prescribed for the treatment of primary and metas- tatic breast cancers. TAM reduces the incidence of estrogen receptor positive breast cancers by about 60 to 70 % in healthy high risk women [1]. Structurally, first generation SERMs are poly-aromatic compounds that contain phenolic moieties which are prone to oxidative metabolism. TAM is a prodrug that is converted into various metabolites with the P450 cytochrome enzymes playing key role in these transformations [2]. The most therapeutically active metabo- lites of TAM are N-desmethyl-4-hydroxytamoxifen (en- doxifen) and 4-hydroxytamoxifen (4-OH-TAM), which are 30- to 100-fold more potent compared to TAM. The anti- estrogenic activities of endoxifen and 4-hydroxytamo-xifen are similar although endoxifen is also a potent inhibitor of aromatase and is present at a higher steady state concentra- tion in patients than 4-hydroxytamoxifen [3]. In addition, TAM was top-ranked among the adverse analytical findings within the hormone antagonists and modulators banned substances in 2010. The latter augmented *Address correspondence to this author at the Benaki Phytopathological Institute, Laboratory of Pesticides Toxicology, 8 St. Delta Street, Athens, Kifissia 14561, Greece; Tel: 00302108180384; Fax: 00302108180223; E-mail: K.Kasiotis@otenet.gr the need for accurate and sensitive analysis of TAM and its metabolites in human biological fluids. Notwithstanding, the increased risk of developing endometrial cancer upon long- term administration of TAM in connection with other toxic- ity parameters, has directed scientists towards the exploita- tion of novel SERMs. Thus, a second generation of SERMs - exemplified by raloxifene (RAL)- along with a third genera- tion was developed [1]. Moreover, various analytical meth- ods were also developed aiming to expand their detectability and include the novel SERMs as well. The corresponding analytical findings suggest the existence of an extensive metabolic pathway -as previously stated- with some metabo- lites being analogues of TAM [4]. Reversed Phase High Performance Liquid Chromatogra- phy (RP-HPLC) is the most widely used technique, espe- cially for water-soluble molecules. Many researchers in- volved in bioanalysis utilize this technique on daily basis to perform a wide range of bioavailability and/or pharmacoki- netic studies. Additionally, RP-HPLC analysis is used as routine choice for the separation-identification of SERMs and their metabolites, while the unambiguous identification provided by mass spectrometry has found merit in drugs and metabolites analysis in conjunction with liquid chromatogra- phy. Advances in the development of silica-based particles have increased the separation efficiency of the HPLC analy- sis. The latest development refers to the application of Ultra HPLC (UHPLC) that uses narrow-bore columns packed with very small particles (below 2 m), which finds numerous applications in SERMs separations (described below) and a plethora of other analytes in various matrices [5]. To increase 2213-2414/14 $58.00+.00 © 2014 Bentham Science Publishers