Exploring the Functional Potential of the Xyrophytic Greek Carob (Ceratonia siliqua, L.) Cold Aqueous and Hydroethanolic Extracts

The present study investigates the antimicrobial, antioxidant, and in vitro antidiabetic potential of cold infusions prepared from different parts of the Greek carob tree (Ceratonia siliqua L.), which is a xerophytic species. Carob samples, including green and ripe pods and leaves, were collected from an urban area of Attica, Greece, and extracted using food-grade solvents (water and a water–ethanol mixture, 90:10, v/v). The extracts were evaluated for antibacterial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 6538 using automated turbidometry. In addition, total phenolic content and antioxidant and antiradical activities were determined via spectrophotometry; the phenolic profile was analyzed using liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QToF-MS), and α-amylase inhibitory activity was assessed through an in vitro assay. All extracts exhibited statistically significant (p < 0.05) bacteriostatic effects, with green pods and leaves showing the highest activity. Ripe pods demonstrated the most potent α-amylase inhibition (up to 96.43%), especially when extracted with water–ethanol mixture (90:10, v/v). Liquid chromatography coupled with tandem quadrupole/time-of-flight mass spectrometry (LC-QToF-MS) analysis revealed a rich phenolic profile across all samples. While carob leaves showed no α-amylase inhibition, their phenolic profile suggests other potential health-related bioactivities. These findings support the development of carob-based functional food products and highlight the nutritional and pharmaceutical potential of this resilient Mediterranean crop.