Green and Sustainable Valorization of Waste Jamun ( Syzygium cumini ) Leaves via Ultrasound‐Enhanced Deep Eutectic Solvent Extraction of Phenolic Compounds

ABSTRACT A sustainable and green extraction strategy combining ultrasound‐assisted extraction (UAE) with deep eutectic solvents (DESs) was developed to valorize Jamun ( Syzygium cumini ) leaves through the recovery of phenolic compounds. Among the evaluated DESs and conventional solvents, choline chloride‐oxalic acid (DES‐5) exhibited the highest efficiency for total phenolic content (TPC) extraction. The DES‐5‐based UAE (DES‐5‐UAE) was found to be a more efficient process than the traditional heating+stirring method. The one‐factor‐at‐a‐time optimization approach identified optimal extraction conditions of 10% V/V water content, 30 min of extraction time, 10:1 liquid–solid ratio, and 40°C temperature, achieving a TPC of 68.24 ± 1.57 mg GAE/g DW. Moreover, the in vitro antioxidant assays revealed the prominent antioxidant activity of Jamun leaves extract based on DES‐5 relative to conventional solvents. The scanning electron microscopic study revealed the efficacy of DES‐5‐UAE in rupturing plant cell walls, thus boosting the extraction of bioactive compounds from the plant matrix. The mass analysis revealed the existence of nine major phenolic compounds in the extract. Stability testing showed 95% TPC retention after 15 days at 40°C. Furthermore, the DES‐5 solvent maintained 70% of its initial extraction efficiency across three reuse cycles.