Cestrum diurnum L., a member of the Solanaceae family, is a widely distributed shrub that is known for its rich phytochemical composition and pharmacological significance. This study aimed to evaluate the phytochemical profile and antioxidant potential of C. diurnum leaf extract. Preliminary phytochemical screening confirmed the presence of alkaloids, saponins, flavonoids, tannins, and phytosterols, which contributed to their therapeutic potential. Quantitative analysis revealed a high concentration of total phenolics (127.23 ± 0.99 mg GAE/g), flavonoids (80.12 ± 1.44 mg RE/g), and tannins (165.47 ± 1.11 mg TAE/g), indicating strong antioxidant properties.

The antioxidant potential of C. diurnum was assessed using DPPH and nitric oxide (NO) free-radical scavenging assays, with ascorbic acid as the standard. The extract exhibited dose-dependent radical scavenging activity, with an IC₅₀ value of 36.29 µg/mL for DPPH and 37.85 µg/mL for NO scavenging, suggesting its potent antioxidant efficacy. These findings indicate that C. diurnum has strong free radical neutralization capacity, which may be beneficial for oxidative stress-related disorders, including osteoporosis.