Natural Deep Eutectic Solvent-Based Extraction of Malva sylvestris L.: Phytochemical Content, Antioxidant and Antimicrobial Potential

What if the greenest solvent isn't water or ethanol, but a mixture that mimics plant cell fluids? A new study on mallow extracts reveals surprising antimicrobial twists.

Mallow, a humble herb found across the globe, has long been prized for its health benefits. But how we extract its bioactive compounds matters as much as the plant itself. In a recent study, scientists compared classic ethanol extraction with two natural deep eutectic solvents (NADES) made from choline chloride paired with either acetic acid or glycerol.

The results were a study in contrasts. Ethanol extracts boasted the highest levels of phenols, flavonoids, and condensed tannins—and excelled in DPPH radical scavenging. Yet NADES-based extracts had their own moments: the glycerol-based solvent (NADES2) showed the best FRAP activity, while the acetic acid-based one (NADES1) displayed notable antibacterial effects against strains like B. cereus and E. coli, though partly due to its low pH.

Antifungal activity, however, was inconsistent with NADES1—ranging from moderate to none, despite the pure solvent's own potency. The researchers found a strong link between phenolic content and antioxidant capacity, but the antifungal puzzle remains unsolved. Future work will need to dig deeper into the mechanisms behind this unexpected behavior, proving that even in green chemistry, nature's complexity always keeps us guessing.

Key Points

• NADES1 (acetic acid) showed strong antibacterial activity, partly due to low pH.
• Ethanolic extracts had highest phenols, flavonoids, and DPPH scavenging.
• NADES2 (glycerol) exhibited highest FRAP antioxidant activity.