Ahmed Taha* and Rema Balachandran
Lithality-guided fractionation of the ethanol extracts of Sesuvium verrucosum , a halophytic plant from Bahrain, lead to the isolation of an active constituent showing a marked significant activity (LC50 =21.4 mg /mL) in the brine shrimp experiment. The plant extracts have been reported to contain alkaloids in leaves, coumarins, sterols and to a lesser extent tannins. We have performed earlier a screening bioassay experiment which showed the plant, in comparison to other plants tested, to possess siginificant cytotoxicity in the crude extract. In this paper we report deconvolution steps of the active ingredient of the plant. The crude extract has been separated into four major fractions(F001-F004). The activity was shown to be residing in fraction F004 (3.5g). A small portion of F004 was tested for the presence of alkaloids using three alkaloid testing reagents and was shown to be positive. The bulk of fraction F004 was subjected to column chromatography on silica gel(60-120 mesh) using gradient elution from hexane-CHCl3(9:1)to CHCl3- EtOH(1:9)(10 fractions, I-X) followed by TLC (SiO2, GF254) analysis. Only fractions VII and VIII (F005) (0.95 g) showed bioactivity (LC50= 21.4 mg/mL). The two fraction were then combined and separated by preparative TLC( SiO2, 1.5 mm layers) into 2 major bands(I & II)and only band II (72 mg) was shown to be active. The chemical structure of the solid separated from band II has been elucidated by GC-MS. GC-MS analysis shows the compound to possess a molecular ion at m/z 251 (%) indicative of a N-containg compound and a base peak at m/z 105 indicative of phenyl ketone fragment.Fragments at m/z 77 and m/z 91 are due to a phenyl ring and a tropylium ion, respectively. A tentative alkaloidal structure is suggested and was given the name: verrucosine.
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