Hemp (Cannabis sativa), or industrial hemp, is an annual herbal plant of the cannabis species that is grown for industrial or medicinal applications. Hemp-derived extracts from the seeds, flowers, leaves or stems are used to make a range of different products – including paper, textiles, biodegradable plastics, biofuel, food and animal feed.
Some natural fibre plants, including hemp, are known to possess antimicrobial activity against a wide range of disease-causing bacteria. As a result, industrial hemp is attracting increasing attention in the search for new classes of antimicrobial agents to combat the rising global health threat of antibiotic resistance. But the potential applications for hemp-derived materials with antibacterial properties extend beyond medications – for example, as natural preservatives in food packaging and cosmetics.
Although there is much anecdotal evidence for the antimicrobial activity of hemp extracts, more rigorous laboratory investigations are needed - to identify the active components and understand their mechanisms of action.
In a new study, published in Separations, researchers set out to isolate and identify compounds with antibacterial activity from industrial hemp leaves.1
The team screened the antibacterial activity of hemp leaf extract against three species of bacteria: Escherichia coli, Staphylococcus aureus, and Bacillus cereus. They found the hemp leaf extract was highly effective at preventing the growth of E. coli and S. aureus – with a minimum inhibitory concentration of 12.5 mg/ml against both organisms. However, it did not affect the growth of B. cereus.
The researchers separated the hemp leaf extract into fractions using high-performance liquid chromatography (HPLC) and screened these for activity against E. coli – identifying two fractions with significant antibacterial activity. Using analytical HPLC, they went on to reveal the identity of the two active compounds as cannabidivarinic acid and cannabidiolic acid.
The team then performed a series of experiments to explore the mechanism of action of these compounds. Both substances destroyed the bacterial cell wall and membrane – resulting in the inhibition of enzyme activity and leakage of contents. Morphological evaluation of the bacterial cell surface using transmission electron microscopy also revealed damage to the cell envelope.
The researchers used deionised water generated by an ELGA laboratory water purification system in these experiments, minimising the risk of introducing contaminants that may affect their results.
This study presents evidence of the antibacterial activity of industrial hemp leaf extract on E. coli and S. aureus. Bioassay-guided fractionation and isolation led to the identification of two compounds – cannabidivarinic acid and cannabidiolic acid – which can prevent the growth of E. coli.
The discovery that cannabidivarinic acid and cannabidiolic acid possess antibacterial activity makes these compounds good candidates for a variety of applications in the food, cosmetic and pharmaceutical industries.
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After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.