Chemical Composition of the Hexane Extract from the Leaves of Solanum pseudocapsicum

INTRODUCTION

Solanum pseudocapsicum L. (Solanaceae), known as winter cherry, is a poisonous plant. It is a cosmopolitan erect and highly branched shrub with non-spiny stems reaching a height of 0.6-1.2 m. It bears small star-shaped flowers with dark-green lanceolate leaves. At maturity, its glabourous red to yellow berries are attractive, hence its cultivation as an indoor ornamental.

Although poisonous, the plant is used for the treatment of acute abdominal pain (Boericke, 1997) boils, gonorrhea and as tonic for men (Batten and Bokelmann, 1966). The hepatoprotective, cytotoxic and antioxidant properties of extracts from the leaves of this plant have been reported (Vijayan et al., 2003, 2004; Badami et al., 2005). Phytochemical studies have revealed the presence of solanocapsine and other alkaloids that are reported to be fatal to man and animals (Der Marderosian et al., 1976; Chakravarty et al., 1984). There is little or no information is available in the literature on the non-polar constituents of this species.

As part of an ongoing study on the documentation of the biological characteristics of this species, hexane extract was fractionated and analyzed by gas chromatography-mass spectrometry. In this study, we report the chemical composition of the hexane fractions from the leaves of S. pseudocapsicum.

MATERIALS AND METHODS

Plant material: The leaves of S. pseudocapsicum was collected from a natural population on the campus of the University of Fort Hare in Alice, South Africa. The plant was authenticated in the Department of Botany and a voucher specimen was prepared and deposited in the Griffen Herbarium of the University of Fort Hare.

Extraction and fractionation: Two hundred grams of the air-dried leaves were pulverized and extracted three times in hexane for a total of 24 h. The extract was filtered and concentrated to dryness under reduced pressure at 40°C to yield 800 mg of extract. The extract (800 mg) was adsorbed in silica gel and later packed into a column of silica gel (0.063-0.200 mm) using vacuum liquid chromatography. The column was eluted with hexane as the mobile phase to yield F1-F3 and thereafter washing with ethyl acetate to give the fourth fraction (F4). After solvent evaporation, the fractions were re-suspended in hexane before the analysis.

GC-MS analysis of the compounds: GC-MS analysis of the volatile components was performed on a Hewlett-Packard HP5973 mass spectrometer interfaced with an HP-6890 gas chromatograph. The following column and temperature conditions were used: Initial temp 70°C, maximum temp 325°C, equilibrium time 1.00 min, ramp 5.0°C min^-1 and final temperature 240°C; inlet: splitless, initial temperature 220°C, pressure 8.27 psi, purge flow 30 mL min^-1, purge time 0.20 min, gas type helium; column: capillary, model number HP 19091M-433, HP-5 trace analysis 5% phenyl methyl, length 30.0 m, nominal diameter 250.0 μm, film thickness 0.25 μm, initial flow 0.7 mL min^-1, initial pressure 8.27 psi, average velocity 32 cm sec^-1, front inlet, outlet MSD; MS: EI method at 70 eV. Peaks were analyzed using the Hewlett-Packard Enhanced Chem Station G1701 BA version b.01.00 programme for Windows. For retention index determinations, n-Alkanes were run under the same conditions.

Identification of the constituents: Constituents of the volatiles were identified by comparison of their Mass Fragmentation (MS) pattern and GC retention times (retention indices) with those of authentic compounds, published references and spectra recorded in the Wiley 275 (Wiley New York) mass spectral library and associated data base (Adams, 1989; Joulain and Koenig, 1998).