Seaweed from the genus Ulva (Ulvales, Chlorophyta) has a worldwide distribution and represents a potential biomass source for biotechnological applications. In the present study, we investigated the ulvan polysaccharide-rich fraction (UPRF) isolated from two Ulva species (U. rigida and U. pseudorotundata), naturally occurring on the Spanish Mediterranean coast. Chemical characterization of UPRFs was performed in order to explore the polysaccharides’ composition. Biological assessments of UPRFs were compared by antioxidant activity and in vitro toxicity tests in the human cell lines: HCT-116 (colon cancer), G-361 (malignant melanoma), U-937 (leukemia), and HaCaT cells (immortalized keratinocytes). Chemical analysis revealed that both UPRFs presented rhamnose as the major relative sugar constituent, followed by glucose in U. rigida and xylose in U. pseudorotundata. Both also presented glucuronic acid, galactose, ribose, and mannose as the remaining monosaccharides. Similar antioxidant activity was obtained, where we observed increased activity in response to increased polysaccharide concentrations. Both UPRFs presented moderate toxicity against HCT-116 cell lines and a selectivity index ≥ 3, suggesting a good potential for use in pharmaceutical products.

石莼属（Ulvales，Chlorophyta）海藻分布于世界各地，是生物技术应用的潜在生物质来源。在本研究中，我们研究了从天然存在于西班牙地中海沿岸的两种石莼物种（U.rigida和U.pseudorotundata ）中分离出的富含绿藻硫化多糖的组分 (UPRF)。对 UPRF 进行化学表征是为了探索多糖的组成。通过人类细胞系中的抗氧化活性和体外毒性测试来比较 UPRF 的生物学评估：HCT-116（结肠癌）、G-361（恶性黑色素瘤）、U-937（白血病）和 HaCaT 细胞（永生化角质形成细胞） 。化学分析表明，两种 UPRF 均以鼠李糖为主要相对糖成分，其次是U.rigida中的葡萄糖和U.pseudorotundata中的木糖。两者还提供葡萄糖醛酸、半乳糖、核糖和甘露糖作为剩余的单糖。获得了类似的抗氧化活性，我们观察到随着多糖浓度的增加，活性增加。两种 UPRF 对 HCT-116 细胞系均表现出中等毒性，选择性指数≥3，表明在医药产品中具有良好的应用潜力。