Natural Antibiotic from Licorice

Researchers have isolated an extract from the roots of the licorice plant that is active against a number of microorganisms that can cause food contamination and which may be an effective natural alternative to chemical preservatives.

Based on the knowledge that licorice, the root and rhizome of the Glycyrrhiza species, has been used for hundreds of years as a natural medicine and therapeutic agent, scientists have been studying various bioactive compounds extracted from the plant. A report in the May 2002 issue of Antimicrobial Agents and Chemotherapy focuses on an extract called licochalcone A and its effect on food spoilage microorganisms.

Scientists from the Higashimaru Shoyu Company (Japan) found that while the extract was not effective against fungi and Gram-negative bacteria, the vegetative cell growth of Bacillus subtilis was totally inhibited by three micrograms per milliliter of licochalcone A. All Bacillus species, as well as other Gram-positive bacteria, were found to be sensitive to the compound. Licochalcone A was resistant to heating at 80 –121oC for 15 minutes. Furthermore, neither high salt concentrations nor proteolytic enzymes had any effect on its antimicrobial activity.

"A recent trend in food processing is to avoid the use of chemical preservatives; thus, natural antimicrobial alternatives are required,” say the researchers. "In the present study, salt-, heat-, and protease-resistant licochalcone A was suggested to be a promising lead compound for the development of agents against spore-forming bacteria.”




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