Physical, Chemical Properties and Biological Activities of Ulvan Extracted From <i>Ulva intestinalis</i> Collected From the Chilika Lagoon

This work investigates the physical and chemical properties and antioxidant activities of ulvan derived from Ulva intestinalis collected from the Chilika lagoon. It showed the highest ulvan content of ∼25.04% under the optimized conditions of 20:1 solvent-to-solid ratio at 90°C for 5 h. The purified ulvan was characterized through X-ray diffraction (XRD), UV-Visible spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), and fourier transform infrared (FTIR). XRD analysis confirmed the predominantly amorphous nature with minor crystalline domains, and UV-Vis spectra confirmed high purity and lack of protein impurities within ulvan. FESEM-EDX indicated its porous and irregular morphology with homogeneously distributed elements, confirming the structure of the sulfated polysaccharide. FTIR revealed the presence of hydroxyl, carboxyl, and sulfate groups within ulvan. Antioxidant activities were measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroxyl, and superoxide radical scavenging assays, ferric reducing antioxidant power, and total antioxidant capacity. Ulvan from Ulva intestinalis displayed potent radical-scavenging activities: DPPH inhibition of 84.9% and superoxide inhibition of 55.5%, comparable to standard ascorbic acid. The high sulfate content (∼20%) contributed significantly to its electron-donating and free radical-neutralizing potential. Overall, the study identifies Ulva intestinalis as a rich source of bioactive ulvan with potential usage in food, nutraceutical, and pharmaceutical sectors.