Impact of Plant Matrix and Extraction Techniques on Phenolic Profiling and Biological Activity of Pomegranate (Punica granatum) peel and Oregano (Origanum vulgare) aerial parts Aqueous Extracts

Abstract

Synthetic fungicides are widely used to control Alternaria alternata, but they can cause resistance and environmental problems. Therefore, safer and natural alternatives are needed. This study investigates aqueous extracts from Origanum vulgare (oregano) aerial parts and Punica granatum (pomegranate) peels, prepared using two extraction methods: ultrasonication method (80ºC for 40 min) and pressurized superheated water (121ºC for 7 min). FT-IR analysis confirmed the presence of phenolic compounds, including rosmarinic acid in oregano and ellagitannins in pomegranate. The extraction method influenced the composition of the extracts: superheated water enhanced carbohydrate-related compounds, while ultrasonication improved phenolic compounds. Pomegranate extracts contained higher total phenolics and tannins, whereas oregano extracts were richer in flavonoids. Antioxidant activity was evaluated using DPPH and FRAP assays. Pomegranate extracts showed stronger antioxidant activity, with lower IC50 values. Antifungal tests showed that both extracts inhibited the growth of A. alternata in a dose-dependent manner. The oregano extract obtained by ultrasonication showed the highest inhibition (85.68%) at 300 mg/mL, while the pomegranate extract obtained by superheated water was more effective at a moderate concentration (150 mg/mL). Additionally, both extracts substantially reduced the spore production of A. alternata compared to the control. These results suggest that plant extracts, especially from pomegranate and oregano, could be used as safe and effective natural biofungicides.