Phytochemical Profiling, Antioxidant Activity, and In Vitro Cytotoxic Potential of Mangrove Avicennia marina

<b>Background:</b><i>Avicennia marina</i> (Forsk.) Vierh., a widely distributed mangrove species, is known for its diverse secondary metabolites with potential pharmacological applications. Despite its dominance in the Arabian Gulf, where <i>A. marina</i> may have adapted to extreme environmental conditions with a distinct set of bioactive molecules, research in this region remains limited. <b>Methods:</b> This study investigates the phytochemical composition, antioxidant activity, and in vitro cytotoxicity of extracts from different plant parts, including roots, leaves, propagules, pericarps, and cotyledons, collected in the United Arab Emirates (UAE). Extracts were analyzed using ultra-pressure liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS). Antioxidant activity was assessed using DPPH and ABTS assays, while cytotoxicity was evaluated against human cancer and normal cell lines. <b>Results:</b> Analysis revealed 49 compounds, including iridoid glycosides, hydroxycinnamic acids, phenylethanoid glycosides, flavonoid glycosides, and triterpene saponins, several reported for the first time in <i>A. marina</i> and mangroves. The pericarp and root extracts exhibited the highest scavenging activity (DPPH: 187.14 ± 2.87 and 128.25 ± 1.12; ABTS: 217.16 ± 2.67 and 147.21 ± 2.42 μmol TE/g, respectively), correlating with phenylethanoid content. The root extract also displayed the highest cytotoxicity, with IC₅₀ values of 58.46, 81.98, and 108.10 μg/mL against MDA-MB-231, SW480, and E705, respectively. In silico analysis identified triterpene saponins as potential contributors. <b>Conclusions:</b> These findings highlight the root extract of <i>A. marina</i> as a promising source of bioactive compounds with potential antioxidant and anticancer applications, supporting further exploration for novel therapeutic candidates.