Carob (Ceratonia siliqua) leaves: A comprehensive analysis of bioactive profile and health-promoting potential of an untapped resource

Carob is a resilient plant with ecological and nutritional significance. A comprehensive study of Ceratonia siliqua leaves (CSL) was conducted to explore its chemical composition and health-promoting potential, aiming at improving the carob-crop sustainability through valorization of this untapped co-product. UHPLC-DAD-HRMS/MS quali-quantitative profiling of CSL revealed high levels of n-galloylated glucoses (129–196 mg g⁻¹) and flavonol-glycosides (36–42 mg g⁻¹), with siliquapyranone (39–56 mg g⁻¹), 1,2,3,6-tetragalloylglusose (47–69 mg g⁻¹) and myricitrin (27–33 mg g⁻¹) as main markers. Highest bioactive content and antioxidant capacity (5.0 and 3.1 TEAC) was obtained during pods harvesting. Besides significant antioxidant potential, CSL exhibited strong-high inhibitory activity against α-glucosidase, acetylcholinesterase and butyrylcholinesterase (IC₅₀, 0.51, 13.5 and 58.0 μg mL⁻¹, respectively). 1,2,3,6-tetragalloylglusose and siliquapyranone are the main contributors to antioxidant and α-glucosidase inhibitory capacities. Excellent ability of extract and 1,2,3,6-tetragalloylglusose (IC₅₀, 0.05 μM) in selectively inhibiting α-glucosidase, make them promising candidates to manage hyperglycemia with fewer side effects.