Advanced extraction techniques for sustainable recovery of health-promoting compounds from carob leaves

Abstract

Carob (Ceratonia siliqua) leaves (CSL) are an underutilized source of health-promoting compounds, including siliquapyranone, 1,2,3,6-tetragalloylglucose and myricitrin. CSL and its main compounds revealed remarkable antioxidant and hypoglycaemic potential. This study presents a systematic optimization of pressurized hot water extraction (PHWE) and probe-based ultrasound-assisted extraction (probe-UAE) as sustainable strategies for the recovery of CSL bioactive compounds. Using response surface methodology combined with UHPLC-UV profiling, the main parameters influencing extraction efficiency and compound stability were identified. Optimal PHWE (98 °C, three 5 min-cycles) and probe-UAE (ethanol 52 %, 100 g L^–1, 20 min) conditions ensured exhaustive recovery of target compounds with negligible formation of extraction artefacts (gallic acid and digalloylglucoses), preserving antioxidant and α-glucosidase inhibitory activities. Compared with conventional techniques, PHWE and probe-UAE demonstrated a low environmental footprint, reducing extraction time, solvent use and environmental impact, while improving extraction yield and extract quality. PHWE generated fully aqueous extracts suitable for direct application, whereas probe-UAE offered high energy efficiency and operational simplicity. These findings demonstrate the potential of green extraction techniques for the sustainable valorization of carob leaves, providing high-value bioactive extracts and supporting the development of healthy food products. This study offers novel insights into the exploitation of untapped plant biomasses and provides a practical approach for integrating green innovations into the food and nutraceutical sectors.