Pharmacological potential of sulfated polygalactopyranosyl-fucopyranan from the brown seaweed Sargassum wightii.

A sulfated polygalactopyranosyl-fucopyranan characterized as ∙∙∙∙ → 1)-α-Fucp-(2SO₃⁻)-(3 → 1)-α-Fucp-(2SO₃⁻)-(4 → 1)-β-Galp-(4 → 1)-β-Galp-(4 → ∙∙∙∙ was isolated from the brown seaweed Sargassum wightii and evaluated for pharmacological properties with reference to antioxidant, anti-inflammatory, antidiabetic, and antihypertensive activities using different in vitro models. The sulfated polygalactopyranosyl-fucopyranan displayed potential di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺) radical scavenging, and Fe²⁺ ion chelating activities (IC₉₀ ~ 1 mg mL⁻¹). The studied polysaccharide displayed higher anti-inflammatory selectivity towards inducive pro-inflammatory enzyme cyclooxygenase-2 (COX-2, IC₉₀ 1.13 mg mL⁻¹) than constitutive cyclooxygenase-1 (COX-1, IC₉₀ > 1.20 mg mL⁻¹) resulting in greater selectivity index (IC₉₀ COX-2/COX-1, 0.93) than synthetic non-steroidal anti-inflammatory drug aspirin (0.88) and also showed potent lipoxygenase-5 inhibition (LOX-5, IC₉₀ 1.02 mg mL⁻¹). The studied polysaccharide displayed significantly higher (P < 0.05) antidiabetic properties compared to the antidiabetic agents acarbose and diprotein-A in terms of α-amylase (IC₉₀ 0.93 mg mL⁻¹), α-glucosidase (IC₉₀ 1.48 mg mL⁻¹), and dipeptidyl peptidase-4 (IC₉₀ 0.11 mg mL⁻¹) enzyme inhibition potentials. The sulfated polygalactopyranosyl-fucopyranan also displayed potential antihypertensive activity with reference to angiotensin-converting enzyme-I inhibitory activity (IC₉₀ 0.2 mg mL⁻¹). Extensive spectroscopic experiments in conjugation with monosaccharide compositional analysis attributed (1 → 3)-linked α-fucopyranose units in the polygalactofucan chain with C-2 sulfation and C-4 substituents as O-acetyl/O-methyl/(1 → 4)-linked β-galactopyranose. The previously undescribed sulfated polygalactopyranosyl-fucopyranan could function as a potential pharmacophore lead against inflammation, type 2 diabetics, hypertension and utilization as natural antioxidant. [ABSTRACT FROM AUTHOR]