As a context, we have been optimizing the DPPH protocol for our seaweed ethanolic extract. We also use varying concentration points from the various methods in published journal articles, yet none have yielded good results. As a gist of the data from our trials, at higher concentrations (i.e., 1000 ppm to 6000 ppm), we keep obtaining a negative %RSA—in this case, this would be reasonable due to the intensity of the colors.

We did another trial, but this time, we prepared concentrations below 1500 ppm.

Firstly, we did a two-fold serial dilution. Here, we found the concentrations 187.5 ppm, 375 ppm, and 750 ppm yielded positive and increasing %RSA values. However, at above 750 ppm and below 187.5 ppm, we obtained negative %RSA values. In that sense, we thought of preparing dilutions from 800 ppm down to 300 ppm, having 100 ppm increments—hoping to obtain good data. Unfortunately, it turned out that our %RSA values were all negative.

Additionally, the color of our extract is green up until 50 ppm. Also, none of the concentrations turn yellow upon reaction with the DPPH. There might be a possibility that the absorbance obtained was only due to the interference of the green pigment in our diluted crude extract.

With everything I've said, would it be safe to conclude that our extract has pro-oxidant activity?