Extract from Chlorella vulgaris: Production, characterization, and effects on the germination, growth and metabolite profile of Eruca sativa microgreens

The increasing demand for sustainable agriculture has intensified interest in natural biostimulants as alternatives to synthetic agrochemicals. Microalgae, particularly Chlorella vulgaris (C. vulgaris), are promising candidates due to their diverse bioactive composition. In this study, we developed a water-based extraction protocol to obtain a polysaccharide-rich aqueous extract (CHL-P) from C. vulgaris and evaluated its effects on early development and metabolite accumulation in Eruca sativa microgreens. The extract was obtained via hot water extraction, then characterized using spectrophotometric, Fourier Transform Infrared Spectroscopy (FTIR), Ultra-High-Performance Liquid Chromatography with Photodiode Array detection (UHPLC-PDA) and High-Resolution Orbitrap Mass Spectrometry (HRMS) techniques. Application of CHL-P at 0.5 mg/mL significantly improved germination rate (+7 %), hypocotyl length (+20 %), and fresh biomass, indicating enhanced early vigor. Biochemically, the treatment triggered a 32 % increase in chlorophyll b, a 7 % increase in total polyphenols, and an 8 % rise in antioxidant activity, suggesting improved physiological and stress-response profiles. UHPLC-PDA analysis further revealed a 2-fold increase in a sinapoyl derivative and a 3-fold increase in dihydrophaseic acid 4-O-beta-D-hexoside, both linked to plant defense and growth regulation. In contrast, higher concentration (1.0 mg/mL) treatments showed no additional benefit and even suppressed key metabolites, indicating a dose-sensitive effect. These findings demonstrate that CHL-P functions as an effective, concentration-dependent biostimulant, enhancing both morphological and metabolic parameters in E. sativa. This study supports the integration of microalgal extracts into clean-label, eco-friendly strategies for crop enhancement.