Phycocolloids from Sargassum microcystum: Immunomodulatory and antioxidant activities of alginic acid and fucoidan Sakthivel Muthu a,* , Ammar B. Altemimi b,c,* , Mythileeswari Lakshmikanthan d , Kathiravan Krishnan d , Qausar Hamed ALKaisy e , Farhang Hameed Awlqadr f , Mohammad Ali Hesarinejad g,* a Centre for Global Health Research, Saveetha Medical College and Hospital, Saveetha Institute of Medical and Technical Sciences (SIMATS), Thandalam, Chennai- 602105, Tamil Nadu, India b Food Science Department, College of Agriculture, University of Basrah 61004, Iraq c College of Medicine, University of Warith Al-Anbiyaa, Karbala, Iraq d Department of Biotechnology, University of Madras, Guindy Campus, Chennai-600025, Tamil Nadu, India e Department of Dairy Science and Technology, College of Food Sciences, University of AL-Qasim Green, Al Qasim, Iraq f Food Science and Quality Control, Halabja Technical College, Sulaimani Polytechnic University, Sulaymaniyah - Iraq g Department of Food Sensory and Cognitive Science, Research Institute of Food Science and Technology (RIFST), Mashhad, Iran A R T I C L E INFO Keywords: Sargassum microcystum Phycocolloids Alginic acid Fucoidan Immunomodulation Antioxidant Biocompatibility ABSTRACT This study focused on isolating and characterizing phycocolloids, particularly alginic acid and fucoidan, from the brown seaweed Sargassum microcystum. Sequential extraction using acetone, chloroform, and methanol yielded various fractions (AIP, ASP, ASPF1, ASPF2, ASPF3). Comprehensive analyses via HPLC, HRGPC, FTIR, and ¹H NMR identified distinct compositions of mannuronic acid, guluronic acid, total sugars, uronic acids, and sulfates across the fractions. Further fractionation of ASP through Q-Sepharose and Sephadex G-100 chromatography revealed homogeneous polymers with molecular weights of 55, 40, and 25 kDa for ASPF1, ASPF2, and ASPF3, respectively. Spectroscopic analyses confirmed AIP as alginic acid, while ASPF2 and ASPF3 were identified as fucoidan. Immunomodulatory assays showed significant IL-10 induction by ASPF3 and concentration-dependent IFN-γ production by ASPF2 and ASPF3 in PBMCs. Additionally, ASPF2 and ASPF3 stimulated NO production in RAW 264.7 cells, with ASPF3 showing the highest induction. ASPF3 demonstrated the highest antioxidant ac- tivity in DPPH, FRAP, HRS, and RP assays, achieving dose-dependent scavenging efficiencies of 73.6 %, 62.6 %, 60.4 %, and 52.4 % at 100 µg/mL. Cell viability assays confirmed the biocompatibility of these phycocolloids. Overall, this study highlights the immunomodulatory, antioxidant, and biocompatible properties of phyco- colloids from S. microcystum, suggesting their potential for diverse industrial applications. 1. Introduction Macroalgae, present in natural ecosystems, have been used for cen- turies in treating various ailments. Despite Earth’s vast biological di- versity, there is untapped potential in exploring novel compounds and bioactive agents, especially from extreme environmental niches (Barbosa et al., 2014; Rosic & Thornber, 2023). The ocean, covering a substantial portion of Earth’s surface and teeming with diverse plant and animal species, offers a rich source for groundbreaking research and the development of pharmaceutical products benefiting human welfare (Silva et al., 2020). The genus Sargassum includes 300 species of brown algae, with some species remaining underexplored for their potential biological activities. Fucoidans, found in Sargassum, exhibit diverse biological activities (Remya et al., 2022). Marine-derived natural products, including those from Sargassum, are undergoing human clinical trials and preclinical development for severe diseases. Despite these advancements, research into marine natural products as pharma- ceutical agents is still in its early stages (Montaser & Luesch, 2011). * Corresponding authors. E-mail addresses: saktthivel@gmail.com (S. Muthu), ammar.ramddan@uobasrah.edu.iq (A.B. Altemimi), mythileeswari@gmail.com (M. Lakshmikanthan), drkkathiravan@gmail.com (K. Krishnan), qayssarhamad@fosci.uoqasim.edu.iq (Q.H. ALKaisy), farhang.hamid.a@spu.edu.iq (F.H. Awlqadr), ma.hesarinejad@ rifst.ac.ir (M.A. Hesarinejad). Contents lists available at ScienceDirect Food Hydrocolloids for Health journal homepage: www.elsevier.com/locate/fhfh https://doi.org/10.1016/j.fhfh.2025.100209 Received 13 November 2024; Received in revised form 7 February 2025; Accepted 9 March 2025 Food Hydrocolloids for Health 7 (2025) 100209 Available online 10 March 2025 2667-0259/© 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by- nc/4.0/).