Antibiotic principle of Eupatorium capillifolium

Area of Science:

• Phytochemistry
• Microbiology
• Natural Product Chemistry

Background:

• Ethanolic extracts of Eupatorium capillifolium (Lam) Small exhibit antimicrobial properties.
• The activity of plant extracts can be influenced by the composition of the growth medium.
• Bacillus subtilis is a common bacterium studied for its susceptibility to antimicrobial agents.

Purpose of the Study:

• To isolate and identify the active principle from Eupatorium capillifolium extracts responsible for antibacterial activity.
• To investigate the mechanism behind the differential activity of the extract against Bacillus subtilis in various media.
• To characterize the chemical nature of the isolated active compound.

Main Methods:

• Extraction of Eupatorium capillifolium using ethanol.
• Bioassay-guided fractionation to isolate the active compound.
• Spectroscopic analysis (including mass spectrometry) for structural elucidation.
• Testing antibacterial activity in both chemically defined and complex natural media.
• Investigating the effect of specific medium components (glutamic acid) on activity.

Main Results:

• An active principle was isolated as a colorless crystalline solid.
• The isolated compound was identified as costic acid, a sesquiterpenic acid.
• Costic acid showed activity against Bacillus subtilis in a chemically defined medium but not in a complex medium.
• Glutamic acid present in the complex medium was found to reverse approximately 90% of costic acid's activity.

Conclusions:

• Eupatorium capillifolium contains costic acid, a sesquiterpenic acid with antibacterial activity against Bacillus subtilis.
• The antibacterial efficacy of costic acid is significantly modulated by the presence of glutamic acid in the growth medium.
• This study highlights the importance of considering medium composition when evaluating the antimicrobial potential of natural products.