Enhanced Extraction and Separation with HPLC-DAD of Phenolic and Flavonoid Antioxidants from Portulaca oleracea L. Leaves Using Tailored Terpenoid-Based NADES: Comparative Assessment of Antiradical and Antimicrobial Activities

Imagine extracting nature's antioxidants with a solvent that's not only green but also outperforms traditional ethanol—this is exactly what terpenoid-based NADES achieve, doubling the yield of key bioactives from purslane leaves.

In the quest for sustainable extraction, scientists have turned to Natural Deep Eutectic Solvents (NADES) as a powerful alternative to conventional ethanol. This study focuses on Portulaca oleracea, commonly known as purslane, a plant rich in phenolic and flavonoid antioxidants. By synthesizing NADES from terpenoids (menthol and β-citronellol) and organic acids (lactic and capric acid), the researchers created solvents with favorable properties—low viscosity, appropriate density, and pH—that remain liquid at room temperature. These tailored NADES significantly outperformed ethanol, with the best formulation (NADES 1) yielding 83.66 Eq GA/mg, 786.55 Eq Q/mg, and 0.78 Eq C/mg compared to ethanol's 58.49, 363.23, and 0.44 respectively. HPLC-DAD analysis revealed that NADES extracts contained higher levels of phenolic acids (caffeic and syringic acid) and flavonoids (rutin and quercetin), which were absent in ethanol extracts. The antioxidant activity, measured by IC50 values, was dramatically superior for NADES extracts (28.10 ± 1.73 µg/µL) versus ethanol (1615.97 ± 5.34 µg/µL), a superiority confirmed by the Trolox method. Additionally, NADES showed enhanced antimicrobial effects, though the efficacy varied with the microorganism. Despite the high viscosity posing a potential limitation, the study suggests that adjusting temperature can improve mass transfer, making NADES a promising, sustainable alternative for extracting bioactive compounds.

Key Points

• NADES outperformed ethanol in extracting antioxidants from purslane leaves.
• NADES 1 yielded highest bioactive contents and superior IC50 values.
• HPLC-DAD identified phenolic acids and flavonoids absent in ethanol extracts.