Optimization of Extraction and HPLC–MS/MS Profiling of Phenolic Compounds from Red Grape Seed Extracts Using Conventional and Deep Eutectic Solvents

What if the secret to better antioxidants was hiding in the waste of your favorite glass of wine? Grape seeds, often discarded, are a treasure trove of bioactive compounds—and we've just found a greener way to unlock them.

Winemaking leaves behind mountains of grape waste—seeds, skin, and stalks. But those seeds are no mere trash; they're packed with phenolic compounds that could benefit health and industry. In this study, researchers optimized the extraction of these compounds from red grape seeds using a statistical design called Box–Behnken. The sweet spot: a 1:10 sample-to-solvent ratio, 30 minutes of extraction, and a gentle 50°C temperature.

To make the process more sustainable, they compared a natural deep eutectic solvent (NADES)—choline chloride:citric acid, or ChCit—with traditional ethanol. Eight red grape varieties were tested, and the extracts were analyzed using HPLC–MS/MS. The results were striking: procyanidin B1, a potent antioxidant, exceeded 1 mg per gram of dry weight in every sample.

Surprisingly, both solvents produced similar levels of phenolics and antioxidant activity. But NADES had a clear edge: it showed a strong affinity for procyanidins and a tight correlation between antioxidant activity and phenolic content. This green solvent could be the future of grape waste valorization—turning a byproduct into a valuable resource.

Key Points

• Optimized extraction: 1:10 ratio, 30 min, 50°C.
• NADES (ChCit) matches ethanol in efficiency, with added benefits.
• Procyanidin B1 exceeds 1 mg/g in all eight grape varieties.