Optimizing extraction techniques for enhanced polyphenol yield from Rheum emodi and Urtica dioica: Comparative analysis of solvent systems and methods

The study optimized polyphenol extraction from Rheum emodi and Urtica dioica, varying solvents (Ethanol, Methanol, Water), concentrations, and extraction methods (CE, MAE, UAE). UAE consistently outperformed, yielding significantly higher phenolics, flavonoids, and antioxidants. In the 60% methanolic extract of U. diocia, the highest antioxidant activities were recorded, with DPPH (69.4 ± 2.2%), ABTS (94.61 ± 2.1%), and FRAP (0.82 ± 0.005 mol Fe2+/g). For Rheum emodi, the 70% ethanolic extract exhibited superior flavonoid content (63.6 ± 2.1 mg RE/g), phenolic content (132.7 ± 2.2 mg E GA/g), and antioxidant activities, including DPPH (69.4 ± 2.2%), ABTS (94.6 ± 2.1%), and FRAP (0.82 ± 0.005 μmol Fe2+/g). HPLC analysis identified eight phenolic acids, five flavonoids, and two anthraquinones in both extracts. These results highlight the potential of Rheum emodi and Urtica dioica as rich sources of phytochemicals for various food and pharmaceutical applications.