engleski

Application of ultrasound-assisted extraction in combination with ethanol to improve antioxidant activity of diatom extracts

Marine microalgae are cellular factories for a wide range of bioactive compounds. Among them, diatoms are an unconventional group that is attracting increasing attention due to their high content of fatty acids, sterols, pigments, etc. In this study, 150 mg of freeze-dried biomass of Skeletonema grevillei and Thalassiosira rotula were extracted in 6 mL of 50% and 70% ethanol assisted with ultrasound for 1 hour. In the extracts, total phenolic content (TFC) and antioxidant activity were determined. Anitoxidant potential was tested by two methods ferric reducing/antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). Prior to the determination of TFC, FRAP, and ORAC, the extracts were concentrated to a volume of 3.5 mL. In 50% ethanol extracts of S. grevillei and T. rotula the TPC was 2.53 and 3.178 mg GAE/g of dry diatom biomass, respectively. The TPC of the 70% ethanol extracts was higher, 2.65 and 5.80 mg GAE /g. Similar activity was determined for the 70% ethanol extracts of S. grevillei and T. rotula by FRAP, 707.69 and 766.67 µm TE, respectively. Similarly, the antioxidant activity of T. rotula extracts tested by ORAC showed higher results for 70% ethanol extract, 39.82 to 58.87 µm TE in comparison to 58.87 obtained for 50% etanolic extracts. On the other hand, the extracts of S. grevillei prepared with 70% ethanol did not show higher antioxidant activity by ORAC. Overall, the antioxidant activity and phenolic content were higher in T. rotula. The obtained results showed that diatoms may be considered as a source of antioxidants, and the knowledge from this study will contribute to the further biotechnological application of diatom and microalgae.

Diatoms ; UAE ; antioxidant capacity

nije evidentirano