Antibacterial activity of extract, fractions and compounds isolated from Abrus precatorius Linn (Fabaceae)

Antibacterial activity of extract, fractions and compounds isolated from Abrus precatorius Linn (Fabaceae)
Mahamat Djamalladine DJAMALLADINE1*, Jean-De-Dieu TAMOKOU2, Laurence VOUTQUENNE-NAZABADIOKO3, Apollinaire TSOPMO4 and David NGNOKAM1
1Research Unit of Environmental and Applied Chemistry, Department of Chemistry, Faculty of Science, University of Dschang, Dschang, Cameroon, 2Research Unit of Microbiology and Antimicrobial Substances, Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon, 3Institute of Molecular Chemisty of Reims, Reims, France. 4Food Science, Department of Chemistry, Carleton University, Ottawa, Canada; *Corresponding author: djamalladinemht@yahoo.fr

In the world, infectious diseases constitute one of the main causes of mortality and morbidity. Plants can play a good role in fight against infectious diseases due to their use in folk medicine. The genus Abrus belongs to the Fabaceae (Leguminoseae) family and includes about 13 species distributed in tropical regions of the world. The seeds of Abrus precatorius are used in traditional medicine to treat malaria, paralysis, dysentery, diarrhoea, ulcer and are reported to have some biological activities such as antifertility, antidiabetic, antiarthritic and antimicrobial properties. The objective of this study was to isolate the secondary metabolites and evaluate the antibacterial activity of extract, fractions and some compounds from the seeds of A. precatorius. The plant material was extracted with MeOH yielding a crude extract which was partitioned with EtOAc, then n-BuOH giving EtOAc and n-BuOH fractions, respectively. By using chromatographic methods, twenty two (22) compounds were isolated from the n-BuOH and EtOAc fractions, including one triterpene, two fatty acids, a mixture of δ and β-sitosterol, two flavonoids, five alcaloids, five phenolic compounds and six saponins. Their structures were elucidated by spectroscopic analysis including 1D-NMR, 2D-NMR and by comparison with literature data. The Minimum Inhibitory Concentrations (MIC) were determined by using the liquid microdilution method in vitro on four bacterial strains including Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi and Enterococcus fecalis. The crude extract, the EtOAc and the n-BuOH fractions were most active with MIC values ranging from 16 to 64 μg/mL against the above microbial strains. Some of the isolated compounds showed moderate activity against the tested strains. Only salicylic acid and gallic acid exhibted significant activity against Enterococcus fecalis and Salmonella typhi with MIC = 8 μg/mL. According to the above results we can continue the investigation with another strains in order to discover a new phytodrug to fight against infectious diseases.
Key words: Abrus precatorius; Fabaceae; Antibacterial activity; Infectious diseases