Isolation of limonoids from seeds of Carapa guianensis Aublet (Meliaceae) by high-speed countercurrent chromatography.
BACKGROUND
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.


METHODS
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-deacetoxy-7-oxogedunin (17.9 mg), deacetylgedunin (3.7 mg), 6alpha-acetoxygedunin (40.1 mg), gedunin (21.0 mg), and andirobin (5.8 mg).


CONCLUSIONS
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.
da Silva
Vagner Pereira
VP
Laboratório de Química de Produtos Naturais, Far-Manguinhos, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
Oliveira
Rodrigo Rodrigues
RR
Figueiredo
Maria Raquel
MR
D003377:Countercurrent Distribution; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D036701:Limonins / Q000737:chemistry / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D029582:Meliaceae / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D012639:Seeds / Q000737:chemistry*; D012997:Solvents
D007202:Indicators and Reagents; D036701:Limonins; D010936:Plant Extracts; D012997:Solvents