Water knotweed is an important candidate for preclinical trials with its high photoprotection and remarkable bioactive properties

Introduction: Persicaria amphibia L. (water knotweed), an edible plant with pharmaceutical properties, is found in Asia, Europe, North America, and Africa. Despite its worldwide distribution and prominence, scientific literature on the plant's therapeutic properties is scarce. This study aimed to comprehensively investigate the antioxidant activity, DNA binding potential, GC-MS, and fluorescence analysis and photoprotective properties of P. amphibia. Method: Water and ethanol maceration and Soxhlet extraction samples (Pa1-4) of P. amphibia were prepared. Bioactive properties of the plant were investigated. Qualitative and quantitative chemical markers of the samples were described using UV-Vis., fluorescence, and gas chromatography-mass spectrometry (GC-MS) analyses, and phytochemical screening. Photoprotective properties of the plant were also revealed using Mansur method. Results: The phenolic and flavonoid contents varied between 22.06 +/- 0.49 and 28.92 +/- 0.51 mu g gallic acid equivalent (GAE)/1 mg and 24.54 +/- 1.19 and 34.09 +/- 0.61 mu g quercetin equivalent (QE)/1 mg, respectively. The fluorescence emission spectra of the samples indicated that the samples may contain berberine alkaloid, and riboflavin and quercetin flavonoids. The sun protection factor (SPF) values revealed that the plant [Pa1 (750 and 1000 mu g/mL = 10.22 +/- 0.05; 13.29 +/- 0.25), Pa2 (500 mu g/mL = 7.58 +/- 0.04) and Pa4 (1000 mu g/mL: 11.86 +/- 0.13)] has more photoprotective activity compared with carrot seed oil (500, 750 and 1000 mu g/mL = 5.22 +/- 0.07; 7.72 +/- 0.09 and 9.69 +/- 0.14) (P > 0.001). Moreover, the samples exhibited considerable antioxidant activity. All four extracts could generally inhibit lipid peroxidation (Pa1-4 = 83.14 % +/- 0.36; 82.05 % +/- 0.82; 80.87 % +/- 0.23 and 81.38 % +/- 1.26) as effectively as the standards of ascorbic acid (81.89 % +/- 0.88) and alpha-tocopherol (85.45 +/- 1.37) for 25 mu g/mL (P > 0.05). The binding affinities between the plant samples and Calf Thymus DNA (CT-DNA) were also determined. The order of the binding affinity is Pa3 > Pa4 > Pa2 > Pa1. Conclusion: The P. amphibia plant has a significant amount and variety of phytocomponents. Along with bioactive and sun protection properties, this plant could be a cheap, beneficial, and safe ingredient for cosmetic and pharmaceutical formulations.