Iranian Walnut (Juglans regia L.) Green Husk as a Source of Functional Compounds: Effect of Extracting Solvents on its Antioxidant and Antibacterial Activities

The current research was conducted to evaluate the effect of different solvents (methanol, ethanol, and water) on bioactive compounds extraction from Iranian walnut (Juglans regia L.) green husks. The results showed that the highest total phenolic content (TPC, 53.50±1.16 mg GAEs/g), total flavonoid content (TFC, 11.90±1.20 mg REs/g), juglone content (JC, 0.22±0.02 mg/g), and antioxidant activity (IC50, 0.66 and 0.22 mg/ml with FRAP and DPPH methods, respectively) was achieved with methanol. All the extracts exhibited antibacterial activity against some pathogenic bacteria in terms of Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Escherichia coli, and Salmonella. But, the methanol extract shown the higher efficiency than water and ethanol extracts. These results revealed that Iranian walnut green husk as agro-by-product can be a potential source of valuable bioactive compounds with medicinal effects.