Characterization of Phenolic and Flavonoid Compounds in <i>Casuarina glauca</i> Organs From Djerba (Tunisia): A Comparative HPLC‐DAD Study of Extraction Techniques

The bioactive compounds of leaves, stems, fruits, and seeds of Casuarina glauca from Djerba, Tunisia, was investigated using maceration and ultrasound-assisted extraction (UAE) techniques. The aqueous extracts were analyzed through high-performance liquid chromatography coupled with a diode-array detector (HPLC-DAD) to identify and quantify bioactive compounds. A total of fifteen compounds were identified, including eight phenolic acids, six flavonoids, and one phenylethanoid glycoside. The HPLC-DAD analysis revealed that catechin was the most abundant compound, particularly in the leaf's extracts, with a concentration of 139.7 mg/mL. Significant variations were observed in the phenolic profiles depending on the extraction technique and the analyzed plant part. Total phenolic content (TPC) and total flavonoid content (TFC) were quantified, indicating that with the use of the UAE method, the leaves extract exhibited the highest level of TPC and TFC (17.53 mg GAE/g dry weight [DW] and 15.43 mg QE/g DW, respectively). Notably, the aqueous leaf extract obtained using UAE exhibited the highest antioxidant activity, as determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays. These results underscore the potential of C. glauca extracts from Tunisia for the first time as valuable sources of natural antioxidants, with promising applications in green pharmacy, complementary medicine, and preventive therapies.