Fucoxanthin extracted and purified from Vietnamese Sargassum oligocystum Montagne, 1845 exhibits various biological activities. In this study, the ability of fucoxanthin to inhibit acetylcholinesterase (AChE), the antioxidant activities, and the expression of antioxidant enzymes were investigated. Fucoxanthin isolated from Vietnamese S. oligocystum showed no cytotoxic effects; moreover, it exhibited AChE inhibitory activity (with an IC₅₀ value of 130.12 ± 6.65 μg mL⁻¹) and antioxidant activity (with an IC₅₀ value of 3.42 ± 0.15 mg mL⁻¹). At concentrations of 50 and 100 µg mL⁻¹, fucoxanthin provided protection against amyloid β-protein fragment 25–35-induced neurotoxicity in a C6 neuronal cell line, and the survival of C6 cells was higher than 81.01% and 80.98%, respectively, compared to the control group (59%). Moreover, antioxidant enzyme activity and quantitative PCR analysis suggested that the neuroprotective effect of fucoxanthin resulted from regulation of the gene expression of antioxidant enzymes (CAT and GPx) and ER pathways (caspase-3 and Bax), as well as the promotion of expression of genes involved in PI3K/Akt signaling (GSK-3β), autophagy (p62 and ATG5), and the biosynthesis of ACh (VAChT and ChAT). Therefore, fucoxanthin extracted from the seaweed S. oligocystum in Vietnam is a potential feedstock source for the production of health foods that exert neuroprotective effects.

This study investigates the suitability of Spirulina-Ogawa-Terui (SOT) culture media with various nutrition concentrations for the laboratory growth of salt-tolerant Spirulina platensis ST. Among the four saltwater mediums, 25% SOT media (42‰ salinity) demonstrated a satisfactory performance, with maximum absorbance at a wavelength 556 nm reading of 0.76. After 15 cultivation days, the protein, carbohydrate, lipid, phycocyanin, chlorophyll a, and carotenoid contents reached 48.73%, 22.14%, 7.32%, 10.23%, 0.53%, and 0.12% of the dry cell weight (DCW), respectively. The growth of S. platensis ST is influenced by the culture medium with a salinity of 13‰ and 52‰, as well as different nutrient compositions. Transcriptional sequencing revealed that the response of S. platensis ST to salt stress was mainly expressed by regulating the gene expression involved in metabolic pathways such as photosynthesis and signaling transduction. Under nutritional and salt stress, S. platensis ST responds by modulating the gene expression involved in the synthesis of vital molecules, for example, growth regulators and adenosine triphosphate (ATP) producers. In conclusion, this study provides an insight into enhancing the ability of S. platensis to tolerate salt stress. The findings indicate that future efforts in algal-based cultivation research in seawater should focus on increasing the productivity to develop a sustainable industry for biomass production.

Background: Haematococcus pluvialis, a green microalga, is a rich source of natural astaxanthin and a potent antioxidant with high commercial value. This study investigates the biological characteristics and potential of H. pluvialis HB isolated from Hoa Binh, Vietnam, for growth and astaxanthin accumulation using a two-phase culture method. Methods: H. pluvialis HB was cultured in a C/RM medium at 25 °C, and morphological characteristics were examined. NMR spectroscopy was used to determine the structure of the astaxanthin, which was extracted using the Soxhlet method. Results: After 22 days, the highest cell density (4.96 × 10⁶ cells mL⁻¹) was achieved under optimized light and ultraviolet conditions. Nutrient deprivation followed by bicarbonate supplementation resulted in a maximal astaxanthin accumulation of 48.8 mg g⁻¹ dry cell weight within two days. The extracted astaxanthin demonstrated potent antioxidant activity (IC₅₀: 3.74 mg mL⁻¹) compared to ascorbic acid (IC₅₀: 18.53 µg mL⁻¹) and exhibited strong acetylcholinesterase inhibition (IC₅₀: 297.99 µg mL⁻¹). It also showed neuroprotective effects against H₂O₂ and amyloid beta-induced neurotoxicity in C6 cells. Conclusions: This study highlights H. pluvialis HB as a promising source for large-scale astaxanthin production with potential applications in neuroprotective health products.

There is a great deal of concern regarding the adverse effects of polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) present in Agent Orange and other herbicides on Vietnam's population and ecosystems. The purpose of this study was to determine the effect of dioxin exposure on adrenal steroids in saliva, and dioxin levels in breast milk, of primiparas in an Agent Orange/dioxin hot-spot and a non-exposed area in Vietnam on the basis of epidemiological research. The subjects were 35 lactating women who had recently given birth to their first or second child. A further sub-study involved eight primiparas from each area. All subjects were aged between 20 and 30 years with infants aged between 4 and 16 weeks. The mean concentration of PCDD, PCDF, and PCDD + PCDF toxic equivalents (TEQ) in breast milk in the hot-spot area was significantly higher than in the non-exposed area. Cortisol and cortisone levels in the saliva of primiparas in the hot-spot area were also significantly higher than those in the non-exposed area. There was a significant negative correlation between cortisol and the cortisol/cortisone ratio and PCDD + PCDF and PCDF TEQ levels in the hot-spot area. Furthermore, the correlation between cortisol and cortisone and the PCDD + PCDF, PCDD, and PCDF TEQ in the combination of hot spot + non-exposed area was significant according to the curve (bell style). Our results suggest that Agent Orange/dioxin exposure still exerts a major influence on the salivary hormones of the Vietnamese population.

Phytochemical investigation of Thraustochytrium aureum led to the isolation of eleven compounds including ergosterol (1), 7-dehydroporiferasterol (2), (22E,24R)-ethylcholesta-7,22-dien-3β,5α,6β-triol (3), poriferasterol glucoside (4), perlolyrine (5), pyrrolezanthine-6-methyl ether (6), 3-(3-aminopropyl)-6-[(4-hydroxyphenyl)methyl]-2,5-piperazinedione (7), 5-methyluracil (8), 1H-indole-3-carboxylic acid (9), adenosine (10), and p-hydroxybenzoic acid (11). Screening for α-glucosidase inhibitory, antimicrobial and cytotoxic activities of the extracts and isolated compounds were carried out. The n-hexane extract was the most active, which showed strong α-glucosidase inhibitory activity with IC50 of 48.22 μg/mL, inhibition against E. faecalis, S. aureus and C. albicans microorganism strains with MIC values of 128, 64 and 64 μg/mL, respectively. Compound 6 have shown to be the most active among isolated compounds, which inhibited α-glucosidase with IC50 value of 7.96 μg/mL; E. faecalis and C. albicans microorganism strains with MIC values of 64 and 16 μg/mL and inhibited the growth of A549, HepG2, MCF7 and LNCaP cancer cell lines with IC50 values of 62.26, 41.03, 57.21 and 43.23 μg/mL, respectively.