Abstract
Introduction: The marine environment is a crucial source of diverse chemical compounds, with macroalgae (seaweeds) providing a sustainable reservoir of bioactive molecules (Guiry, 2013). Algal polysaccharides are valuable for health and industrial applications, documented for their anti-inflammatory, antioxidant, and antiviral effects (Stengel et al., 2011). Iran’s extensive Persian Gulf coast possesses substantial, yet underexplored, potential for exploiting native algal flora, as comprehensive local species data remains scarce. More recent research (since 2020) has emphasized advanced extraction techniques, such as Microwave-Assisted Extraction (MAE) or enzyme-assisted methods, to improve both efficiency and purity (Dobrinčić et al., 2020; Yahyavi et al., 2018). Furthermore, novel applications such as antiviral activity and effects on gut microbiota have been increasingly reported in species like Enteromorpha clathrata (Yao et al., 2022; Huang et al., 2025). This study addresses the research gap concerning native Persian Gulf species. Its core objective is to conduct a comparative quantitative and qualitative assessment of water-soluble polysaccharides from three endemic species: the green alga Enteromorpha clathrata, the red alga Laurencia snyderae, and the brown alga Padina gymnospora. Findings enable industrial use of local marine resources.
Materials and Methods: Specimens of the green alga Enteromorpha clathrata, the red alga Laurencia snyderae, and the brown alga Padina gymnospora were collected from the intertidal and subtidal zones of the Persian Gulf near Lengeh Fishery Research Center station in November 2019. Species identity was confirmed by a marine phycologist. The precise identification of the collected algal species from the Persian Gulf coasts was verified using specialized regional resources (Ghoranjik and Rouhani Ghadeiklaii, 2010). After collection, samples were washed to remove salts and adherent foreign matter, then freeze-dried (Brebion, 2013). The extraction process commenced with pigment and partial protein removal using repeated soaking in 96% ethanol at 70°C (Liu et al., 2016). Water-soluble polysaccharides were subsequently extracted using a conventional hot water method (70°C, 10:1 ratio) repeated for three cycles. The crude extract was clarified by centrifugation and filtration. Purification aimed at removing secondary metabolites and proteins involved the Sevag method (chloroform/n-butanol) (Liu et al., 2012), followed by a color removal step using Amberlite XAD7 resin (Brebion, 2013). Polysaccharides were precipitated with 96% ethanol, recovered via centrifugation, and freeze-dried for yield measurement (Hosseini-Nezhad, 2006). Total carbohydrate content and purity were determined spectrophometrically using the Phenol-Sulfuric Acid method with Glucose as the standard (Southgate, 1991). Statistical analysis utilized one-way analysis of variance (ANOVA) followed by Tukey’s post-hoc test, with significance set at p < 0.05 (SPSS 26).
Results and Discussion: The investigation revealed a clear, statistically significant differentiation in both the yield and purity of extracted polysaccharides across the three species, reflecting the unique cell wall composition of the Chlorophyta, Rhodophyta, and Phaeophyta divisions.Extraction Yields were highest in the brown alga Padina gymnospora, which demonstrated 1.26% efficiency, consistent with the known high solubility of phaeophycean polysaccharides like fucoidans and alginates in hot water (Stengel ets al., 2011). Conversely, the green alga Enteromorpha clathrata showed the lowest yield (0.29%), with the red alga Laurencia snyderae in the middle (0.46%). In terms of polysaccharide Purity, Laurencia snyderae was superior, achieving the highest mean purity of 82.98%, followed by E. clathrata (80.74%). P. gymnospora yielded the lowest purity at 75.83%. Statistical analysis confirmed a significant quality difference between P. gymnospora and L. snyderae (p=0.044).The inverse relationship between high yield and low purity in P. gymnospora highlights a key limitation of the conventional hot water extraction method, which non-selectively co-extracts non-carbohydrate impurities, particularly phenolic compounds. However, the subsequent use of the Sevag method and Amberlite XAD7 resin was effective in reducing the final phenol content. The high purity and the observed gel-forming characteristic of the L. snyderae extract strongly suggest the presence of valuable phycocolloids, such as carrageenans, critical for the food and pharmaceutical industries (Van de Velde and Guinchard, 2009). These findings corroborate existing reports on the distinct functional potential of these genera, including antithrombotic activity in E. clathrata and antibacterial properties in P. gymnospora. Furthermore, the highly sulfated structures impart significant potential as prebiotics and strong antiviral capabilities (Yao et al., 2022; Huang et al., 2025). To maximize the commercial value of the high-yield P. gymnospora extract, future studies must explore advanced, selective extraction techniques like Microwave-Assisted Extraction (MAE) or Ultrasound-Assisted Extraction (UAE) to minimize phenolic contamination (Dobrinčić et al., 2020). Finally, since the current products were prepared using Lab Grade solvents, extensive purification using Food Grade solvents and mandatory rigorous safety and cytotoxicity testing are essential prerequisites for any commercial or therapeutic application.
Conclusion: This research successfully established that the native Persian Gulf algal species, Enteromorpha clathrata, Laurencia snyderae, and Padina gymnospora, represent valuable and distinct sources of water-soluble polysaccharides. The key conclusion is that the species should be targeted based on application: Padina gymnospora is the optimal source for high-volume industrial applications due to its maximum extraction yield of 1.26%, while Laurencia snyderae is the superior candidate for high-value biomedical and pharmaceutical applications, owing to its significantly higher purity of 82.98%. The observed differences in yield and purity directly reflect the unique cell wall structures and polysaccharide composition of the Chlorophyta, Rhodophyta, and Phaeophyta divisions. These findings provide a vital, evidence-based roadmap for the targeted and sustainable exploitation of these regional marine bio-resources. Given the highly promising characteristics identified, several avenues for future research are highly recommended. Firstly, comprehensive structural elucidation of the isolated polysaccharides is necessary to fully correlate their molecular architecture with their observed or predicted biological activities. practical studies focusing on the upscaling of the extraction process using Food Grade solvents and advanced techniques (MAE/UAE) are necessary to bridge the gap between laboratory findings and commercial production, thereby supporting the growth of the national marine biotechnology sector. Finally, given the promising results, this research can inspire broader studies in the field of marine ecopharmacology and significantly contribute to the development of biotechnology industries in the country.
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