The latest episode in the American Chemical Society's (ACS') award-winning Global Challenges/Chemistry Solutions podcast series reports that an antibacterial extract from the leaves of the carob tree (the source of a popular chocolate substitute) could fight the microbe responsible for the serious form of food poisoning called listeriosis.

Based on a report by Pierluigi Caboni, Ph.D., Nadhem Aissani and colleagues in ACS' Journal of Agricultural and Food Chemistry, the new podcast is available without charge at iTunes and from http://www.acs.org/globalchallenges.

In the new episode, Caboni explains that the increase in antibiotic-resistant bacteria, so-called superbugs, has fostered a search for new natural substances to preserve food and control disease-causing microbes. They cite a need for new substances to combat Listeria monocytogenes, bacteria that caused food poisoning outbreaks in a dozen states with at least three deaths last year.

Carob has attracted attention as a potential antibacterial substance, but until now, scientists had not tested it against Listeria. Carob may be best-known as a substitute for chocolate that does not contain caffeine or theobromine, which makes chocolate toxic to dogs.

Their report describes tests in which extracts of carob leaves proved effective in inhibiting the growth of Listeria bacteria growing in laboratory cultures. Further, it offers a possible explanation for the antibacterial action. The results were promising enough for the scientists to plan further tests of carob extracts on Listeria growing in meat and fish samples.