Volatile and Phenolic Compounds in Freshwater Diatom Nitzschia palea as a Potential Oxidative Damage Protective and Anti‑Inflammatory Source

Background: Nitzschia palea is a freshwater diatom species (Bacillariophyceae), is easy to cultivate, and is a primary producer of organic matters in aquatic environments. Materials and Methods: In this study, proximate composition in axenic culture of N. palea was determined, phenolic content and volatile compounds were determined for methanol and ethyl acetate extracts. Both the extracts were evaluated for eight different in vitro antioxidant and free radical scavenging activities. Macromolecular damage prevention properties were determined by electrophoretic methods, and antihemolytic activity was validated by lactate dehydrogenase assay, atomic force microscope, and scanning electron microscope image analysis. Results: Both the extracts showed antioxidant, macromolecular damage prevention, and antihemolytic properties. Among the two extracts, ethyl acetate extract showed high activity compared to methanol extract. Based on this result, ethyl acetate extract was evaluated for in vitro anti‑inflammatory properties using RAW 264.7 cells. The extract showed IC50 value of 50.73 µg/mL and inhibition of inflammatory cytokines such as nitric oxide, tumor necrosis factor‑alpha, and prostaglandin E2. The observed activity was correlated with identified important metabolites such as butyl isobutyl phthalate, pristane, and squalene of methanol extracts. Similar co-relation was observed for 7,9‑di‑tert‑butyl‑1‑oxaspiro (4,5) deca‑6,9‑diene‑2,8‑dione, methyl palmitate, hentriacontane, and dibutyl phthalate were of ethyl acetate extract. Conclusion: The study concludes that N. palea has potentiality to isolate pharmacologically active metabolites using advanced chromatographic techniques, which can be useful in combating oxidative stress‑related inflammatory diseases.