The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid extractor with carbon dioxide as the extraction medium and a FT-IR spectrometer equipped with a mercury cadmium telluride detector (MCT). The shape of extraction curves obtained during the monitoring was used to decide when to stop the supercritical fluid extraction (SFE). No significant density dependence of the molar absorption coefficient or wavenumber of the C=O stretching vibration (v(C=O)) of tagitinin C at 1668 cm(-1) was noticed. The physical characteristics of SCCO2 governing the extraction yield of the active component from leaves were optimized by means of a central composite design (CCD). The studied variables were temperature (40, 60 and 80 degrees C) and pressure (8.0, 14.0 and 20.0 MPa) of the supercritical fluid. The composition profile of T diversifolia extracts obtained by SFE was investigated in the range from 3400 to 2600 cm(-1) according to the pressure and temperature conditions of SCCO2. The qualitative approach of the extracts composition was accomplished through the CH stretching vibrations (nu(CH)) of components. (c) 2006 Elsevier B.V. All rights reserved.