STEROIDAL GLYCOSIDES OF FURCRAEA SELLOEA AND THEIR BIOLOGICAL PROPERTIES AGAINST DIFFERENT SCHISTOSOMA MANSONI STAGES

Furcraea selloea C. Koch dry powder (Family Agavaceae) was subjected to a bioassayguided fractionation technique to isolate the active constituents responsible for the potency of this plant. The antischistosomal impact of different extracts of the leaves of F. selloea was screened against adult Schistosoma mansoni worms in vitro using a well established culture media. The methanol extract of the plant showed the highest activity as S. mansoni worms recorded 100% mortality at 50 μg/ml after 24 hours. Owing to the high potency of the crude saponins obtained from the methanolic extract (100% mortality at 20 μg/ml),it was submitted to chromatographic separation using silica gel and Sephadex columns as well as preparative thin layer chromatography. Three steroidal saponins (I-III) were isolated and their structures were elucidated using some spectroscopic and chemical methods as follows: 6-O -Dglucopyranosyl (1  4) -D-glucopyranoside chlorogenin (I), 3-O -D-glucopyranosyl-(1  4) -D-glucopyranoside crestagenin (II) and 3-O -D-glucopyranosyl-(1  3) -D- glucopyranosyl-(1  3) -D-xylopyranoside gloriogenin (III). Bioassay screening of the isolated saponins (I-III) were carried out against certain Schistosoma mansoni stages. Compound III only proved to possess antischistosomal activity against S. mansoni worms at concentration as low as 5 μg/ml, while compounds I and II were inactive. Also, test against B. alexandrina snails revealed that only saponin III has high molluscicidal activity (LC90 = 6 ppm) whereas the other two saponins did not show any activity up to 50 ppm after 24 hours exposure. Different concentrations of the crude and the isolated saponins were evaluated against S. mansoni free larval stages (cercariae and miracidia). Hatchability of S. mansoni ova was markedly depressed when exposed to 6 ppm of compound III. The infection rate of B. alexandrina snails was significantly reduced when snails were exposed to three sublethal concentrations of the dry plant powder. Determination of the acute oral toxicity of F. selloea methanol extract against mice was carried out. When three groups of mice infected with S. mansoni were treated orally with a single dose of 2500 mg/kg of F. selloea methanol extract either at 2, 4 or 7 weeks post infection, the reduction rate in worm load was significantly lower when compared to infected untreated control.