Determination of antioxidant capacity of watercress (Nasturtium officinale)

Watercress (Nasturtium officinale) is an aquatic plant belonging to the Brassicaceae family. In this study, in vitro, antioxidant capacities and antimicrobial activities of different extracts of Nasturtium officinale plant collected from Kayseri province were determined by different methods. In addition, the phenolic compounds, volatile components, minerals, and fatty acids contained in the plant were determined. At the same time, the antioxidant capacity and antimicrobial activity of quinic acid, which was found in excess in Nasturtium officinale, was determined and compared with the Nasturtium officinale plant. Thus, the effect of quinic acid on the antioxidant and antimicrobial properties of the plant was investigated. The antioxidant capacity of Nasturtium officinale's water and methanol extracts and quinic acid were determined in vitro by seven different methods (DPPH, ABTS, DMPD, KUPRAK, FRAP, Fe3+ reduction, total antioxidant determination). In addition, the antimicrobial activities of Nasturtium officinale's water and methanol extracts, and quinic acid were examined by the disk diffusion method. In addition, the phenolic components of Nasturtium officinale were determined by LC-MS/MS using different methods and different solvents, and it was shown how the phenolic compounds contained in the plant were affected by different solvents and different extraction methods. In addition, volatile components of Nasturtium officinale in GC-MS device, fatty acids in GC-FID device, and beneficial minerals in ICP-MS device were determined. In conclusion, in the presented study, besides revealing the antioxidant capacity and antimicrobial effects of water and methanol extracts of Nasturtium officinale, it was determined that Nasturtium officinale is both rich in phenolic compounds and volatile components and is a good mineral source containing essential fatty acids. It was found that the plant is rich in quinic acid and α-terpinolene, and it is a valuable species that contains many components that were previously known to have antioxidant, antimicrobial, anticarcinogenic, and anti-inflammatory properties. In addition, it was determined that quinic acid has a strong antimicrobial effect and thus contributes to the antimicrobial activity of the plant.