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

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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 (IC 50 , 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 (IC 50 , 0.05 μM) in selectively inhibiting α-glucosidase, make them promising candidates to manage hyperglycemia with fewer side effects. • Carob leaves are a valuable and sustainable source of bioactive compounds. • Highest leaf-bioactive content coincides with the harvest time of ripe pods. • CSL can positively affect wellness and reduce the risk of noncommunicable diseases. • CSL and TeGG are strong selective α-GLU inhibitors with hypoglycaemic potential. • CSL emerges as a potential health-promoting ingredient in healthy food products.