Ulvan, a sulfated heteropolysaccharide with structural and functional properties of interest for various uses, was extracted from the green seaweed Ulva papenfussii. U. papenfussii is an unexplored Ulva species found in the South China Sea along the central coast of Vietnam. Based on dry weight, the ulvan yield was ~15% (w/w) and the ulvan had a sulfate content of 13.4 wt%. The compositional constitution encompassed L-Rhamnose (Rhap), D-Xylose (Xylp), D-Glucuronic acid (GlcAp), L-Iduronic acid (IdoAp), D-Galactose (Galp), and D-Glucose (Glcp) with a molar ratio of 1:0.19:0.35:0.52:0.05:0.11, respectively. The structure of ulvan was determined using High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FT-IR), and Nuclear Magnetic Resonance spectroscopy (NMR) methods. The results showed that the extracted ulvan comprised a mixture of two different structural forms, namely (“A3s”) with the repeating disaccharide [→4)-β-D-GlcAp-(1→4)-α-L-Rhap 3S-(1→]n, and (“B3s”) with the repeating disaccharide [→4)-α-L-IdoAp-(1→4)-α-L-Rhap 3S(1→]n. The relative abundance of A3s, and B3s was 1:1.5, respectively. The potential anticarcinogenic attributes of ulvan were evaluated against a trilogy of human cancer cell lineages. Concomitantly, Quantitative Structure–Activity Relationship (QSAR) modeling was also conducted to predict potential adverse reactions stemming from pharmacological interactions. The ulvan showed significant antitumor growth activity against hepatocellular carcinoma (IC₅₀ ≈ 90 µg/mL), human breast cancer cells (IC₅₀ ≈ 85 µg/mL), and cervical cancer cells (IC₅₀ ≈ 67 µg/mL). The QSAR models demonstrated acceptable predictive power, and seven toxicity indications confirmed the safety of ulvan, warranting its candidacy for further in vivo testing and applications as a biologically active pharmaceutical source for human disease treatment.

The high-performance liquid chromatography method coupled with diode array and mass spectrometric detector (HPLC-DAD-MS) method for quinonoid pigment identification and quantification in sea urchin samples was developed and validated. The composition and quantitative ratio of the quinonoid pigments of the shells of 16 species of sea urchins, collected in the temperate (Sea of Japan) and tropical (South-China Sea) climatic zones of the Pacific Ocean over several years, were studied. The compositions of the quinonoid pigments of sea urchins Maretia planulata, Scaphechinus griseus, Laganum decagonale and Phyllacanthus imperialis were studied for the first time. A study of the composition of the quinonoid pigments of the coelomic fluid of ten species of sea urchins was conducted. The composition of quinonoid pigments of Echinarachnius parma jelly-like egg membrane, of Scaphechinus mirabilis developing embryos and pluteus, was reported for the first time. In the case of Scaphechinus mirabilis, we have shown that the compositions of pigment granules of the shell epidermis, coelomic fluid, egg membrane, developing embryos and pluteus are different, which should enable a fuller understanding of the functions of pigments at different stages of life.

This study investigates seasonal biomass variations in Betaphycus gelatinus, a red alga cultivated in the field in Ninh Thuan, Vietnam, along with the chemical composition, structural properties, and bioactivity of its carrageenan. Monthly measurements over a one-year period revealed peak growth (2.02% per day) and carrageenan yield (59.61%) in June, identifying it as the optimal harvest period. FTIR and NMR analyses of carrageenan extracted from field-cultivated B. gelatinus showed hybrid κ- and β-carrageenan forms and a unique pyruvylated β-carrageenan structure not previously reported for this species. Bioactivity assays indicated high antioxidant potential, with a total antioxidant capacity equivalent to 48.30 mg ascorbic acid/g carrageenan and an ABTS radical scavenging IC50 of 3.64 µg/mL. Additionally, antibacterial tests demonstrated strong inhibition of Listeria monocytogenes (12.00 mm inhibition zone). These findings suggest that field cultivation is a sustainable approach for carrageenan production, yielding bioactive compounds with promising applications in pharmaceuticals, cosmetics, and food preservation as a viable alternative to wild harvesting.