Optimization, purification, and antioxidant activity analysis of intracellular acidic sugars in desert microalgae GTD4C-2
Desert microalgae, a special type of algae that grows in desert environments, are rich in protein, oil, and polysaccharides. Meanwhile, due to its high oil accumulation capacity, desert microalgae is considered a promising new biofuel resource; Polysaccharides, on the other hand, have attracted widespread attention in the food, feed, and pharmaceutical industries due to their various functions such as anti coagulation, antioxidant, and antibacterial. It is necessary to isolate and purify polysaccharides from desert microalgae for better application. The composition and structure of polysaccharides are crucial for exploring their functions. The size of molecular weight, monosaccharide composition, and carbon chain functional groups are all related to their biological activity.
Polysaccharides are classified into acidic, neutral, and alkaline polysaccharides based on whether they contain specific functional groups. Acidic polysaccharides have good anti-tumor effects and have a positive impact on the immune system, which has been widely studied. The content of sulfate groups on their sugar chain backbone is related to their growth environment. Studies have shown that sulfated polysaccharides are mainly found in marine algae, as well as some mammals (invertebrates), fish skins, and a few plants in saline alkali environments. Most terrestrial plants do not have them because sulfate groups can be used to resist extreme environments such as high salt and high alkali, and the content of sulfate groups is closely related to biological activity.
This experiment used a central composite design (CCD) to optimize the extraction process of intracellular polysaccharides (IPSs) from desert microalgae, which can better and more accurately evaluate experimental data and lay a good foundation for further detection of IPSs structure and function. Research on polysaccharides has always been a hot topic, especially in marine algae, which are more favored by the public in terms of functionality and safety. However, there is relatively little research on polysaccharides in desert microalgae.

Desert Chlorella has strong salt alkali and drought resistance, but there is relatively little research on its polysaccharide extraction and antioxidant activity detection. This article optimizes the extraction process of IPSs from desert microalgae, and conducts separation, purification, and activity detection. The CCD method was used to optimize the IPSs extraction process, and the highest IPSs extraction amount was achieved under the conditions of temperature of 80 ° C, time of 1 hour, and solid-liquid ratio (g/mL) of 1:25. Two acidic polysaccharides, IPS-2 and IPS-3, were successfully separated by ion chromatography, with sulfate content of (5.69 ± 0.11)% and (8.46 ± 0.03)%, respectively. Meanwhile, IPSs, IPS-2, and IPS-3 samples are mainly composed of glucose and galactose. The IPSs of desert microalgae showed an inhibitory effect on DP-PH free radicals with an IC50 of 0.011mg/mL, which is close to the IC50 of VC on DPPH free radicals at 0.007mg/mL; In terms of hydroxyl radicals, IPSs of desert microalgae showed an inhibitory effect with an IC50 of 0.737mg/mL, which is also close to the IC50 of 0.626mg/mL of VC on hydroxyl radicals. This extremely strong antioxidant activity may be related to the monosaccharide composition (glucose) content. The research results of this article provide a literature basis for the structure and activity of polysaccharides from desert microalgae, and lay an academic foundation for the development of potential products in multiple fields such as food, medicine, cosmetics, etc. The research results were published in the 7th issue of Natural Product Research and Development in 2024