Structural and chemical characterization of polysaccharides from the red alga Plocamium cartilagineum (Linnaeus) P.S. Dixon 1967 with antiviral, anti-angiogenic, and anti-inflammatory activities

Marine algae are abundant in marine ecosystems and represent a valuable source of bioactive compounds. This study reports the extraction and characterization of the sulfated polysaccharide fraction (PCPS) from the Moroccan red alga Plocamium cartilagineum. The antiviral, anti-angiogenic, and anti-inflammatory activities of the cell wall sulfated polysaccharide (PCPS) were evaluated. The biochemical composition of PCPS was analyzed by quantifying total sugar, protein, uronic acid, polyphenol, and sulfate group contents. The structural characteristics of the extract were investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, scanning electron microscopy, and high-performance liquid chromatography coupled with mass spectrometry. The extraction yield of PCPS was 11.63 ± 0.13 %, with sugars (72.06 ± 0.18 %) and sulfate groups (12.27 ± 0.06 %). FTIR confirmed the presence of sulfated polysaccharides, while XRD indicated a semi-crystalline to amorphous transition. HPLC-MS identified galactose, arabinose, and glucose, classifying PCPS as a heteropolysaccharide. PCPS exhibited strong antiviral activity against HSV-1 (EC₅₀ = 3.84 ± 2.8 μg/mL), anti-inflammatory effects by inhibiting phospholipase A₂ and elastase (IC₅₀ = 0.138 and 1.34 μg/mL, respectively), and anti-angiogenic properties, reducing vessel formation in the chorioallantoic membrane assay by 46.26 %. These findings highlight the pharmaceutical potential of P. cartilagineum polysaccharides.