Phytochemical and Bioactive Analysis of Extracted Brown Macroalgae ( <i>Dictyota implexa</i> ) Collected in Vietnam

Brown algae are considered a marine algae resource for human health. This study investigated ethanol extract's chemical composition and biological activity from brown algae <i>Dictyota implexa.</i> The extract from <i>D. implexa</i> was examined for total contents of quercetin, tannic acid, phenolic, flavonoid, polysaccharides, agar, and fucoidan, and the antioxidant, anti-inflammatory, antibacterial, cytotoxic, and α-amylase inhibitory activities of the crude extract were determined. Results revealed the presence of a source of phenolic (85.95 ± 1.21 mg GAE/g of the sample), flavonoid (245.6 ± 2.83 mg QE/g of the sample), and tannin (172.179 mg/g DW) compounds in the extract. Evaluating antioxidant activity proved the ethanol extract of <i>D. implexa</i> possessed the highest activity on two testing methods of DPPH scavenging capacity and reducing power. Besides, the anti-inflammatory activity was potent in the extract with an IC₅₀ value of 9.95 ± 1.51 μg/mL. Concerning antimicrobial activities, the ethanol extract of <i>D. implexa</i> (70 mg/mL) showed potential inhibitory ability against <i>E. coli</i> and <i>B. cereus</i>. Moreover, the algal extract displayed cytotoxic activity against HeLa cells and inhibited α-amylase activity with an IC₅₀ value of 276.82 μg/mL. The current findings demonstrated that exploring novel natural resources offers a promising avenue for advancements in human health and economic well-being.