What does a berry shrub have anything to do with antibiotics? A new study explains how the American beautyberry boosts the antibiotic efficacy against staph bacteria.
A collaboration between Emory University in Atlanta, Georgia, and the University of Notre Dame, Indiana published their findings in the American Chemical Society's Infectious Diseases journal. Their research highlights how beautyberry leaves contain a compound that works with a penicillin antibiotic to fight methicillin-resistant Staphylococcus aureus (MRSA).
American beautyberry, also known as French mulberry, is a native perennial shrub that grows in southern states. The shrub grows between five to eight feet tall and grows clusters of purple and blue berries in between the leaves during springtime.
"We decided to investigate the chemical properties of the American beautyberry because it was an important medicinal plant for Native Americans," said Professor Cassandra Quave from Emory University's Center for the Study of Human Health and Emory School of Medicine's Department of Dermatology. Her team at the Emory Antibiotic Center also pursues the field of medical ethnobotany--how indigenous tribes use plants for healing practices.
American Beautyberry Leaves
In the early 1900s, farmers crushed beautyberry leaves as a mosquito repellent on their horses, mules, and themselves. Native American tribes such as the Choctaw, Creek, and the Seminole also made use of its roots, branches, and leaves to treat several illnesses such as malaria, stomachaches, dizziness, and colic, or babies frequently crying intensely for a prolonged time.
When Quave studied the shrub extracts used as mosquito and tick repellant as well as treating bacteria that causes acne, her team discovered how it affects the behavior of antibiotics against staph infections. Using beautyberry leaves, they discovered a compound that complements the antibiotic oxacillin.
"Even a single plant tissue can contain hundreds of unique molecules," Quave explained. "It's a painstaking process to chemically separate them out, then test and retest until you find one that's effective."
The compound they identified is part of a group of chemicals called clerodane diterpenoids. Some of these compounds repel predators such as insects or may have a bitter taste.
Combining Beautyberry & Antibiotics
The team discovered that the compound can inhibit MRSA infection from spreading. Since the chemicals were only partially effective against staph infection, the team combined it with beta-lactam antibiotics.
"Beta-lactam antibiotics are some of the safest and least toxic that are currently available in the antibiotic arsenal," Quave said. "Unfortunately, MRSA has developed resistance to them."
Their experiments revealed that beautyberry leaf extract plus oxacillin, a type of beta-lactam antibiotic, had good synergy. Together, they broke down MRSA's antibiotic resistance.
Next, the team will be working on testing the antibiotic resistance combination on animal models to measure its efficacy. If MRSA infections can be warded off, the scientists can synthesize the plant compound and alter its chemical structure to create a new combination therapy with the beta-lactam antibiotic.
"We need to keep filling the drug-discovery pipeline with innovative solutions, including potential combination therapies, to address the ongoing and growing problem of antibiotic resistance," Quave said. "Even in the midst of the COVID-19, we can't forget about the issue of antibiotic resistance."