Chemical Profiling and Immune-Stimulating Activity of Solvent Fractions Derived from Dietary <i>Chlorella</i>

Chlorella, a genus of single-celled green algae, is widely industrially cultivated as a dietary supplement ingredient due to its high protein content and various nutrients. In this study, the immune-stimulating effect of solvent fractions prepared from <i>Chlorella vulgaris</i> (CV) and <i>Chlorella protothecoides</i> (CP) was evaluated through the expression of immune-related factors, such as TNF-α and IFN-γ in T cells obtained from mice. Both <i>Chlorella</i> species showed immunostimulatory effects in hexane and butanol fractions, but CV increased TNF-α only, while CP elevated both TNF-α and IFN-γ. In addition, the lipid profile of <i>Chlorella</i> was characterized using non-selective LC-MS/MS-based metabolomic analysis. According to the lipidomic results, the two species differed in lipid composition, with PC 32:1, PC 32:2, PC 34:5, DGDG 34:4, and DGDG 34:5 being enriched in the active fractions of CV, and PC 34:1, PC 34:2, PC O-15:2 and DGTS 34:4 being abundant in the fractions of CP. Furthermore, 5'-methylthioadenosine (MTA), which was detected in both <i>Chlorella</i> species, also exhibited immunostimulatory properties.