Analytica Chimica Acta 575 (2006) 290–299 Partial least squares-based multivariate spectral calibration method for simultaneous determination of beta-carboline derivatives in Peganum harmala seed extracts Bahram Hemmateenejad a,b,∗ , Abdolkarim Abbaspour a , Homeyra Maghami a , Ramin Miri b , Mohhamad Reza Panjehshahin b a Chemistry Department, Shiraz University, Shiraz 714545, Iran b Medicinal & Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Received 7 March 2006; received in revised form 17 May 2006; accepted 29 May 2006 Available online 6 June 2006 Abstract The partial least squares regression method has been applied for simultaneous spectrophotometric determination of harmine, harmane, harmalol and harmaline in Peganum harmala L. (Zygophyllaceae) seeds. The effect of pH was optimized employing multivariate definition of selectivity and sensitivity and best results were obtained in basic media (pH > 9). The calibration models were optimized for number of latent variables by the cross-validation procedure. Determinations were made over the concentration range of 0.15–10 g mL -1 . The proposed method was validated by applying it to the analysis of the -carbolines in synthetic quaternary mixtures of media at pH 9 and 11. The relative standard errors of prediction were less than 4% in most cases. Analysis of P. harmala seeds by the proposed models for contents of the -carboline derivatives resulted in 1.84%, 0.16%, 0.25% and 3.90% for harmine, harmane, harmaline and harmalol, respectively. The results were validated against an existing HPLC method and it no significant differences were observed between the results of two methods. © 2006 Elsevier B.V. All rights reserved. Keywords: Harmine; Harmane; Harmaline; Harmalol; Multivariate calibration; Partial least squares 1. Introduction Peganum harmala L. (Zygophyllaceae) is a poisonous plant that grows in Central Asia, North Africa and the Middle East [1]. It is also widespread in Iran. P. harmala has been used in Iran and Turkey for ritual purification for driving away evil sprits by burning the seeds [2–4]. Seeds of P. harmala L. contain alka- loids such as harmine, harmaline, harmalol and harmane (Fig. 1), which are derived from -carboline (Cs) and tetrahydo-- carboline (THCs). These alkaloids can be found naturally in foods following condensation between indoleamines and alde- hydes or -keto acids [5]. This reaction may occur during food production, processing and storage. Also, these alkaloids have been reported to be found in some alcoholic beverages and foodstuffs [5]. Different biological activities have been reported ∗ Corresponding author. Tel.: +98 711 2284822; fax: +98 711 2286008. E-mail address: hemmatb@sums.ac.ir (B. Hemmateenejad). for harmine and the other related alkaloids in the seeds of P. harmala. In addition to their effects on the CNS [6] and cardio- vascular system [7], there are reports of antimicrobial [8] and cytotoxic activities [3] and human DNA topoisomerase I inhi- bition [9] by -carbolines. Several methods have been developed for the quantitation of beta-carboline derivatives. HPLC with fluorimetric, chemilumi- nescence and mass spectrometry detection are the predominantly analytical methods used for identification, separation and deter- mination of beta-carboline and tetrahydrobeta-carboline deriva- tives [10–14]. Peroxyoxalate chemiluminescence [15] and flow injection potentiometric [16] methods have also been reported for the analysis of beta-carboline derivatives. The simultaneous determinations of harmane, harmalol, harmine and harmaline in the seeds of P. harmala by using of HPLC and TLC have been reported [17,18]. Gas chromatographic analysis of the com- pounds utilizing chemical derivitization is also reported, where problems due to possible artifacts formation during derivati- zation may also occur [5]. The chromatographic methods are, 0003-2670/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2006.05.093