<p>Leaf, stem and root of <em>Chromolaena odorata</em> were extracted by maceration extraction method using water, ethanol, methanol and hexane as solvents. The average percentage yield of leaf extracts in water (12.16 ± 0.13%), ethanol (8.42 ± 0.115%), methanol (10.45 ± 0.012%) and hexane (2.37 ± 0.215%) were significantly higher compared with stem and root extracts using the same solvents. All extracts were tested for antimicrobial activity against ten bacterial strains associated with human skin infections. Leaf extracts with ethanol, methanol and hexane solvents gave the best inhibitory activity against six gram-positive bacterial strains (<em>Bacillus cereus</em> TISTR 687, <em>Enterococcus faecalis </em>TISTR 379, <em>Staphylococcus epidermidis </em>TISTR 518, <em>Staphylococcus aureus </em>TISTR 1466, <em>Streptococcus pyogenes </em>ATCC 19615 and <em>Propionibacterium acnes</em> DMST 14916) and one gram-negative bacterial strain (<em>Proteus vulgaris </em>ATCC 13315). The hexane stem extract showed greater inhibitory activity against <em>Pseudomonas aeruginosa </em>ATCC 27853(15.3±0.5 mm), <em>B. cereus</em> TISTR 687(14.6±0.8 mm) and <em>Klebsiella pneumoniae</em> TISTR 1843 (14.0±1.0 mm), while hexane root extract showed high inhibitory activity against <em>Enterococcus faecalis </em>TISTR 379 (14.5±0.9 mm) and <em>Kleb. pneumoniae</em> TISTR 1843 (14.7±0.6 mm). The lowest minimum inhibitory concentration (MIC) of the ethanolic leaf extract was 0.81 mg/mL against <em>Staph. aureus </em>TISTR 1466, followed by methanolic and hexane leaf extracts with equal MIC of 1.62 mg/mL against both <em>Staph. aureus </em>TISTR 1466 and <em>Strep. pyogenes </em>ATCC 19615. The antimicrobial activity of the methanolic leaf extract of <em>C. odorata </em>was correlated with the amount of both total phenolic and flavonoid compounds. The results obtained suggest that the ethanolic, methanolic and hexane leaf extracts could be developed to treat bacterial skin infections. The hexane was sutiable solvent for extraction of the stem and root parts of <em>C. odorata</em>.</p>
Both neem extract and azadirachtin are widely used in agriculture as organic pesticides because they are nontoxic to humans, animals, and the environment. However, their effects on soil microorganisms and plant growth-promoting rhizobacteria (PGPR), which directly affect soil quality, remain largely unexplored. In this study, the effects of neem extract and azadirachtin on the activity of soil microbes and rhizosphere microorganisms was evaluated. We found that 0.1 and 0.4 gmL -1 of the extract and 1.25 and 2.5 µgmL -1 of azadirachtin inhibited the activity of soil microorganisms in vitro. Treating soil with azadirachtin for two months reduced the number of microorganisms present, while two months of treatment with neem extract increased the number of microorganisms in both the soil and the rhizosphere. The phytopathogenic bacterium Pectobacterium carotovorum was more resistant to azadirachtin than Rhizobium sp. Moreover, treatment of mung beans with neem extract or azadirachtin reduced the number of root nodules and Trichoderma asperellum in the rhizosphere, when compared to the control.
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