The increasing absorbance in your nitric oxide antioxidant assay may indicate that the plant extract or silver nanoparticles generate nitric oxide instead of scavenging it, potentially due to pro-oxidant effects. Additionally, assay conditions or interference from other compounds could contribute to this unexpected result.

yes, we have tackle the same issue. it is due to the inconsistent lightening on your test mixture, which will precipitate as non-dose dependent inhibition of pink coloration. Another factor is buffer system so choose the appropriate buffer system and adjust the pH as well.

Thank you for your responses

I find it difficult to answer. I am not familiar with the procedure of your experiment. Perhaps your reaction mixture contains different concentrations of reducing agents. They can reduce nitrites to nitrates.