Evaluation of antimicrobial activity of a lectin isolated and purified from Indigofera heterantha

Abstract

Indigoferaheterantha commonly called indigo bush is amember of leguminoseae family found in the Himalayan region of Kashmir. Alectin has been isolated from the seeds of Indigoferaheterantha by the purification procedure involving anion exchange chromatographyon DEAE-cellulose followed by gel filtration chromatography on Sephadex G 100.Molecular characterization of the lectin was done by gel filtration andSDS-PAGE. Activity of the lectin was checked by hemagglutination assay and thesugar specificity by sugar inhibition tests. The antimicrobial activity of thepurified lectin was carried out by Agar disc diffusion using appropriatestandards. On the ion exchange column, the bound protein when eluted with 0-0.5 M NaCl gradient emerged as three peaks—peak I, peak II and peak III out ofwhich only peak II showed the hemagglutinating activity. The lectin furtherresolved into two peaks G1 and G2 on gel filtration, with the lectin activityresiding in G1, corresponding to a molecular weight of 70 KDa. The purifiedlectin named as Indigofera heterantha Lectin(IHL) produced a single band on SDS PAGE (18 KDa), revealing the tetramericnature of the lectin. It agglutinated human erythrocytes (A, B, AB, and O).Hemagglutination was inhibited by D-galactose, Dmannose and D-arabinose. Thelectin is reasonably thermostable showing full activity within a temperaturerange of 30&degC to 90&degC. pH stability of the lectin falls in the range of 2-9.IHL demonstrated a remarkable antibacterial activity against the pathogenicbacteria Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. IHL also inhibited the growth ofphytopathogenic fungi Aspergillus niger, Aspergillus oryzae and Fusarium oxysporum.