Green chemistry strategies for Flavonol extraction from onion: Exploring natural deep eutectic solvents

Forget harsh chemicals—what if the secret to unlocking onion's health-boosting flavonols lies in a simple, eco-friendly mixture? Scientists just found a greener way to extract these compounds, and it's faster too.

Onions are packed with flavonols—natural compounds linked to health benefits—but getting them out usually requires harsh solvents like methanol. That's where natural deep eutectic solvents (NaDES) step in, offering a sustainable alternative that's both effective and kind to the planet. In this study, researchers tested choline chloride-based NaDES with various partners and ratios to find the best match for onion flavonol extraction. The winning combination was choline chloride with levulinic acid at a 1:2 ratio, which efficiently pulled out five major flavonols, including quercetin glucosides and isorhamnetin derivatives. Using a Box-Behnken design, they fine-tuned the extraction conditions—water content, temperature, and time—to maximize yields. The optimized method delivered 4.83 ± 0.05 mg of flavonols per gram of onion, with good precision (RSD < 10%), and took only minutes instead of hours. Compared to traditional solvents like methanol and ethanol, the NaDES approach matched or even exceeded their performance, all while being greener. This breakthrough positions NaDES as a promising, sustainable tool for future food chemistry, proving that going green doesn't mean sacrificing efficiency.

Key Points

• Choline chloride:levulinic acid (1:2) best for onion flavonols
• Optimized NaDES yields 4.83 mg/g with RSD < 10%
• Green alternative matches or beats traditional solvents