The ABTS•+ radical cation was produced by reacting 7.4 mM ABTS and 2.6 mM potassium persulfate solutions (1:1) and stored in the dark at room temperature for 12 h and then diluting with methanol to get an absorbance of 1.1 ± 0.02 at 734 nm. Plant extracts (150µl) at 200µg/ml was mixed with ABTS•+ solution (2850 µl) and then incubated at dark for 2 hr. Absorbance was found to be 0.218 at 734nm. Trolox standard is prepared from 50 to 600µM. The equation of trolox is y = -0.0010x + 0.6713, R2 = 0.9968. Most of the paper followed in the Re et al (1999) was expressed in % inhibition or IC50 or trolox equivalent and its ABTS•+ solution was diluted to 0.7 absorbance. But I don’t find any paper expressed in % inhibition for the protocol which I have followed. Can it express in % inhibition using the same protocol or it should express as µM TE/g? If it should express in trolox equaivalent, then how can it calculate? Please help me
Hi jag,
For the ABTS assay, the Re et al. method is the best. For the first time I saw this protocol. If you are getting the good calibration curve then its ok, you can use following equation to calculate % scavenging
ABTS cation radical scavenging activity (%) = [(A blank - A sample) / A blank] x 100
It is always good to show activity in terms of IC50 value. even for protocol you have used, you can calculate activity in terms of IC50. For that you have to prepare series of various conc. of your sample solutions and evaluate them all for the ABTS assay. Further you need to find value at 50% inhibition and that will be your IC50 value.
Sending herewith one of my article, you can go through it.
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