Bioactivity and Phytochemical Characterization of <i>Ceriops decandra</i> (Griff.) Ding Hou. Leaves: HPLC‐DAD Profiling, Antioxidant, Antimicrobial, and Antidiarrheal Potentials

Ceriops decandra (Griff.) Ding Hou, a mangrove species (family: Rhizophoraceae), has been traditionally used for its medicinal properties. This study investigates the phytochemical composition along with antioxidant, antimicrobial, and antidiarrheal potentials of C. decandra extracts. Successive extraction was performed using n-hexane, dichloromethane (DCM), ethyl-acetate (EtOAc), and ethanol (EtOH). The polyphenolic profile was analyzed employing High-performance liquid chromatography with diode array detection (HPLC-DAD) technique. Antioxidant evaluations were performed through total phenolic, flavonoid, and tannin contents, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and Fe²⁺ chelation assays. Antimicrobial and antidiarrheal activities were evaluated using disc diffusion and castor oil-induced models, respectively. The EtOH and EtOAc extracts showed the highest phenolic (110.43 ± 0.0510 and 93.59 ± 0.0005 mg/g), flavonoid (3.88 ± 0.0017 and 6.15 ± 0.0006 mg/g), and tannin contents (3.65 ± 0.0006 and 3.99 ± 0.0015 mg/g), whereas the EtOH extract exhibited strong antioxidant activity IC₅₀: DPPH (7.08 ± 0.47 µg/mL), ABTS (6.35 ± 0.21 µg/mL), and Fe²⁺ chelation (18.20 ± 0.66 µg/mL). HPLC-DAD analysis identified 10 polyphenolic compounds, with EtOAc extract containing the highest levels of quercetin. Antimicrobial activity of the extracts was also prominent, whereas the DCM fraction demonstrated significant antidiarrheal effect. The outcome supported the traditional use of C. decandra as a source of natural antioxidant, antimicrobial, and antidiarrheal candidate, highlighting potential pharmacological attributes.