In vitro Antibacterial Activity of n-Hexane Fraction of Methanolic Extract of Alstonia scholaris L. R.Br. Stem Bark against Some Multidrug Resistant Human Pathogenic Bacteria

Plants are a source of wide range of bioactive molecules. Alstonia scholaris, a tree species of Apocynaceae family is being reported as a well known herbal remedy of various diseases. In the present investigation, n-hexane fraction of crude methanolic extract of Alstonia scholaris Linn. R.Br. stem bark was evaluated for antibacterial activity using four human pathogenic multi-drug resistance bacterial strains Enterobacteriaceae bacterium IK1_01, Shigella dysentery, Enterobacter cloacae and Serratia marcescens. Antibiotic susceptibility tests were also performed to evaluate the multi-drug resistance patterns of these strains. All the strains showed multi-drug resistance against several commercially available antibiotics. The n-hexane fraction showed significant inhibitory activities against all the strains by agar-diffusion assay. The n-hexane fraction of crude methanolic extract of stem of A. scholaris showed MICs of 5.5 mg/ml, 5 mg/ml, <5.5 mg/ml and 8 mg/ml, and induced a maximum of 85.7%, 95.6%, 89.3% and 94.4% growth inhibition against E. bacterium IK1_01, S. dysentery, E. cloacae and S. marcescens, respectively.