Koushik Mondal Variations in the results of radical scavenging assays across different doses of samples can be attributed to several factors. Mostly it is due to Concentration-Dependent Activity. Antioxidant compounds often follow a dose-dependent activity curve, but the relationship isn't always linear. At lower doses, the concentration of the compound might be insufficient to neutralize the free radicals effectively. At higher doses, saturation effects or side reactions may occur, leading to reduced efficiency or variations.

Also if the sample is crude, the interactions between components matters. If the sample contains a mixture of compounds, these compounds might interact with each other. At higher concentrations, these interactions could result in synergistic or antagonistic effects, influencing the scavenging activity.

Solubility of compounds also need to be considered because, Poor solubility at certain concentrations can affect the availability of active compounds to interact with radicals. Insoluble compounds may aggregate or precipitate, reducing their effectiveness. The assay-specific sensitivity to antioxidants in the sample could be another possible reason.

The solution is to optimize experimental conditions, test a wide dose range, use proper controls, and replicate measurements to reduce variability. You can perform multiple replicates to reduce variability and calculate average values with standard deviations.