Isolation of Limonoids from Seeds of Carapa guianensis Aublet (Meliaceae) by High-Speed Countercurrent Chromatography

Introduction - Limonoids are tetranortriterpenoids of considerable interest due to their structural varieties and biological activities, such as insecticidal, antibacterial, antifungal, antimalarial, anticancer and antiviral. They contain oxygen atoms that confer a moderate polarity and are responsible for the difficulties in their separation by traditional chromatographic methods. High-speed countercurrent chromatography (HSCCC) is a versatile liquid-liquid separation technique, in which the sample is distributed between two non-miscible phases to achieve separation. Objective - To isolate limonoids from a complex Carapa guianensis seed extract by gradient elution HSCCC and to identify them by spectrometric and spectroscopic methods. Methodology - The hexane extract of Carapa guianensis squeezed seeds was prepared by Soxhlet extraction. From this extract, 800 mg were submitted to gradient mode HSCCC, using the solvent systems hexane:ethyl acetate:methanol:water 1:2:X:1, X = 1.5 (system A) and X = 1.75 (system B). The upper organic phase of the system A was used as stationary phase, and the lower aqueous phases of both systems as mobile phases. In this procedure, 165 fractions of 4 mL (660 mL) were collected. Results - Six compounds were isolated. Spectrometric and spectroscopic analysis allowed the identification of the substances, as follows: methyl angolensate (28.7 mg), 7-descetoxy-7-oxogedunin (117.9 mg), deacetylgedunin (3.7 mg), 6 alpha-acetoxygedunin (40.1 mg), gedunin (21.0 mg), and andirobin (5.8 mg). Conclusion - The use of gradient mode in HSCCC was a good alternative, exploiting small variations of partition coefficient between the substances. Thus it was possible to isolate them in a good relative abundance, compared with classical chromatographic methods. Copyright (C) 2008 John Wiley & Sons, Ltd.