Antimicrobial Effectiveness of Ribes nigrum L. Leaf Extracts Prepared in Natural Deep Eutectic Solvents (NaDESs)

Blackcurrant leaves are more than just a pretty shrub—they pack a punch against bacteria and fungi. But the secret to unlocking their power lies in a green, natural solvent.

Blackcurrant leaves have long been known as treasure troves of bioactive compounds—phenolic acids, flavonoids, and tannins. These molecules are behind the plant's antioxidant, anti-inflammatory, and antimicrobial prowess. But how do we get the most out of them? The answer may lie in natural deep eutectic solvents, or NaDESs, a new generation of green solvents that are both effective and environmentally friendly.

In this study, scientists used two hydrogen-bond acceptors and three hydrogen-bond donors to create various NaDESs. They tweaked the molar ratio, water content, extraction time, and used two techniques: ultrasound-assisted extraction (UAE) and ultra-turrax extraction (UTE). The goal? To maximize the yield of polyphenols and flavonoids while keeping antioxidant activity high.

Results were promising. UAE produced extracts with higher polyphenol concentrations and stronger antioxidant activity. Liquid chromatography-mass spectrometry revealed that chlorogenic acid dominated the mix. When tested against a panel of microbes—four Gram-positive bacteria, three Gram-negative bacteria, and the fungus Candida albicans—the extracts showed significant activity against Gram-positive strains and the fungus.

These findings confirm that NaDESs are not just a green alternative but an enhancer for polyphenol extraction. Blackcurrant leaves, prepared this way, could pave the way for new therapeutic formulations, harnessing nature's own chemistry for our benefit.

Key Points

• UAE yielded higher polyphenols and antioxidant activity.
• Chlorogenic acid was the predominant compound.
• Extracts active against Gram-positive bacteria and Candida albicans.