ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Biological evaluation and molecular docking of sulfated polysaccharide-derived glucuronic acid from S. platensis as a potential inhibitor of SARS-CoV-2 ORF3a and Envelope (E) proteins

Mythili Ravichandran, Mohammed Al-zharani, Fahd A. Nasr, Lina M. Alneghery, J. M. Mohamed, T. T. Ajith Kumar, B. T. Sureshkumar, and R. Dineshkumar

Department of Microbiology, Vivekanandha Arts and Science College for Women, Sankagiri, Salem, India

E-mail: dineshram625@gmail.com

Received: 24 March 2025  Accepted: 9 June 2025

Abstract:

Sulfated polysaccharides from microalgae are promising antiviral agents owing to their unique biochemical properties. In this study, we evaluated the antiviral potential of polysaccharides extracted from Spirulina platensis isolated from Aliyar Dam, Tamil Nadu, India. We hypothesized that d-glucuronic acid (GlcA), a major monosaccharide in the extract, inhibits the SARS-CoV-2 accessory proteins, Open Reading Frame 3a (ORF3a) and Envelope (E). It was cultured in Zarrouk’s medium, exhibited its characteristic helical morphology. Polysaccharides were extracted by hot water extraction, yielded 4.12% biomass with 10.18% polysaccharides. The biochemical composition of the extract included 42.62 mg g⁻¹ protein, 485.34 mg g⁻¹ carbohydrate, 219.55 mg g⁻¹ sulfate, and 163.17 mg g⁻¹ uronic acid. The monosaccharide profiling was identified as rhamnose (42.3%) and glucose (37.6%) as the dominant sugars. Furthermore, UV–vis spectroscopy showed absorption peaks at 210 and 280 nm, confirmed the presence of polysaccharides and proteins. FTIR analysis revealed the functional groups characteristic of sulfated polysaccharides, including hydroxyl, carbonyl, and glycosidic linkages. Moreover, molecular docking of GlcA was performed against SARS-CoV-2 ORF3a and E proteins using PatchDock and FireDock, yielded binding energies ranging from − 69.12 to − 98.64 kcal mol⁻¹ and − 7.27 to − 58.11 kcal mol⁻¹, respectively. Key hydrogen-bonding and electrostatic interactions indicated the strong affinity of GlcA for these viral targets. This study uniquely combines the biochemical characterization of Spirulina platensis polysaccharides with molecular docking of the dominant monosaccharide, GlcA, against SARS-CoV-2 proteins. This integrated approach elucidates the specific antiviral mechanisms of microalgal compounds. These findings suggest that GlcA derived from S. platensis holds promise as a potential antiviral agent against COVID-19.

Graphical abstract

Graphical abstract for molecular docking and biological evaluation of S. platensis-derived glucuronic acid against SARS-CoV-2 ORF3a and E proteins

Keywords: Antiviral activity; d-Glucuronic acid; Envelope (E) protein; Molecular docking; ORF3a protein; Polysaccharides; SARS-CoV-2; Spirulina platensis

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04213-2

Chemical Papers 79 (10) 6681–6697 (2025)