Italian scientists have found a surprisingly potent antibacterial compound in an extract from the leaves of the carob tree — the source of the popular chocolate substitute — that is particularly effective against the bacteria that cause the serious food-poisoning illness listeriosis.
The discovery, reported by Pierluigi Caboni, Nadhem Aissani and colleagues in the American Chemical Society’s Journal of Agricultural and Food Chemistry, could give doctors a new weapon in the fight against antibiotic-resistant “superbugs” that cause many infections each year.
Caboni — a researcher with the Department of Life and Environment Sciences at the University of Cagliari, Italy — said the increase in drug-resistant bacteria is driving research into new and natural substances to preserve food and control disease-causing microbes, such as Listeria monocytogenes, the microbe that caused food poisoning outbreaks in a dozen states and three confirmed deaths last year.
“In recent years, there has been great development in the search for new natural compounds for food preservation aimed at a partial or total replacement of currently popular antimicrobial chemicals,” the researchers said. “[This study shows] carob [Ceratonia siliqua] offers a natural promising alternative for food safety and bioconservation.”
Past studies have shown that carob, best known as a substitute for chocolate that does not contain caffeine or theobromine, has antibacterial properties, but scientists had not tested it against Listeria until now.
The new research demonstrated that extracts of carob leaves blocked the growth of Listeria bacteria in laboratory tests. The scientists now plan to test carob extracts on Listeria growing in meat and fish samples.