Phytochemical Compounds and Biological Properties of Carob Pods (Ceratonia siliqua L.) Extracts at Different Ripening Stages

Ceratonia siliqua L. pods have been classically used in Mediterranean folk medicine as a potential source of natural antibacterial and antioxidant agents. The in vitro antiradical, immunostimulant, antibacterial and cytotoxic properties, as well as phytochemical composition of the ethanolic and aqueous extracts obtained from carob pods harvested at three ripening stages were assessed. Fructose, glucose, and sucrose, as quantified in both extracts, showed varied yields according to the ripening stage and solvent type. Likewise, significant differences were shown in bioactive compounds content depending on extraction solvent and ripening stage. Moreover, gilthead seabream ( Sparus aurata L.) leucocyte viability and functions were not altered after being incubated for 24 h with the extracts of carob pods. On the other hand, the ethanolic extracts (0.75 and 1 mg mL −1 ), exhibited an interesting cytotoxic effect on a tumoricidal fish cell line (PLHC-1 cell). Besides, the ethanolic extract (1 mg mL −1 ) displayed a moderate bactericidal activity against different examined bacteria. Photobacterium damselae was found to be the most sensitive to different carob pod extracts, except for the aqueous extract obtained from ripened pods. While Vibrio harveyi and Vibrio anguillarum exhibited a strong resistance against the aqueous extracts. Our data indicate that the carob pods are an excellent source of natural bioactive molecules that would be used to prevent and treat several marine animal diseases. Graphical Abstract