Microwave-assisted extraction of bioactive compounds from Urtica dioica using solvent-based process optimization and characterization

Stinging nettle, the plant that seems to bite back, may hold the key to greener antioxidant extraction—if we just microwave it right.

Nettle leaves are a botanical treasure chest, packed with phenolics, flavonoids, and minerals. But to unlock their bioactive bounty, scientists need the right solvent and the right conditions. This study turned to microwave-assisted extraction, a fast and green technology, and compared water, 80% ethanol, and a natural deep eutectic solvent (NADES) made from choline chloride and lactic acid.

Using a statistical design called RSM-BBD, the team optimized power, time, and sample-to-solvent ratio for each solvent. The best results emerged at low power—300 W—with short times (10–17 minutes) and modest solvent volumes. For NADES, the sweet spot was 300 W, 10 minutes, and a 1:13 ratio.

The optimized extracts were then tested for antioxidant power (TPC, TFC, DPPH, ABTS, FRAP) and antimicrobial activity against three pathogenic bacteria: Staphylococcus aureus, Streptococcus pyogenes, and E. coli. Advanced analyses via U-HPLC, GC-MS, and LC-MS revealed the chemical profiles.

The verdict? NADES (ChCl: lactic acid) proved a standout, delivering high antioxidant activity and good antimicrobial potential. This green solvent could be a game-changer for nettle-based nutraceuticals and pharmaceuticals.

Key Points

• NADES (ChCl: lactic acid) yields high antioxidant activity
• Optimum: 300 W, 10–17 min, low solvent ratios
• Extracts fight Staphylococcus, Streptococcus, and E. coli