Talanta 71 (2007) 911–917 Direct determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres E. Zi´ emons a,∗ , V. Barillaro b , E. Rozet a , N. Wandji Mbakop a , R. Lejeune a , L. Angenot c , L. Thunus a , Ph. Hubert a a Laboratory of Analytical Chemistry, University of Li` ege, Department of Pharmacy, CHU, Tour 4, Avenue de l’Hˆ opital 1, B-4000 Li` ege, Belgium b Laboratory of Pharmaceutical Technology, University of Li` ege, Department of Pharmacy, CHU, Tour 4, Avenue de l’Hˆ opital 1, B-4000 Li` ege, Belgium c Laboratory of Pharmacognosy, University of Li` ege, Department of Pharmacy, CHU, Tour 4, Avenue de l’Hˆ opital 1, B-4000 Li` ege, Belgium Received 27 January 2006; received in revised form 17 May 2006; accepted 26 May 2006 Available online 3 July 2006 Abstract Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration of curves obtained by plotting the absorbance of the highly specific C O stretching vibration at 1668 cm -1 versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500–2500 g of added amount of tagitinin C). The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound. © 2006 Elsevier B.V. All rights reserved. Keywords: On-line detection; Supercritical fluid extraction; FT-IR spectroscopy; Tagitinin C; Tithonia diversifolia; Accuracy profile 1. Introduction Tithonia diversifolia (Hemsley) A. Gray (Asteraceae) is a shrub which is native to Mexico and also grows in parts of Africa and Asia. Extracts of this plant have been used tradition- ally for the treatment of diarrhea, fever and malaria. Recently, the antimalarial properties of T. diversifolia against Plasmodium falciparum were investigated in vitro by Goffin et al. [1]. Tag- itinin C (Fig. 1) was identified as an active component against Plasmodium. An additional work of Gu et al. [2] showed signif- icant antiproliferative activity of tagitinin C. ∗ Corresponding author. Tel.: +32 4 3664324; fax: +32 4 3664317. E-mail address: eziemons@ulg.ac.be (E. Zi´ emons). In the last decade, supercritical fluid extraction (SFE) pro- cessing with carbon dioxide has emerged as the alternative to the conventional solvent extraction (e.g. maceration, perco- lation, Soxhlet, microwave extraction and accelerated solvent extraction) of natural products for foods and medicines. Indeed, carbon dioxide is an inert, inexpensive, easily available, odour- less, tasteless and environment-friendly solvent avoiding any solvent residue in the extract because of its gas state under the ambient conditions. Moreover, the near-ambient critical temper- ature of carbon dioxide (31.1 ◦ C) makes it ideally suitable for the extraction of thermolabile natural products by reducing the risks of degradation or volatilisation of the compounds under investigation. In addition, as on-line technique is less tedious and time- consuming than off-line analysis, SFE has been coupled to a 0039-9140/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2006.05.076