Q55. Free radical scavenging activity of a medicinally important plant extract can be quantified by
Answer: (A) ABTS method
The ABTS (2,2′-azino-bis-(3-ethyl benzothiazoline-6-sulphonic acid)) method is the correct choice for quantifying free radical scavenging activity in medicinally important plant extracts.
Option Breakdown
(A) ABTS Method
ABTS involves generating a stable radical cation (ABTS- +) that turns blue-green, which antioxidants in plant extracts decolorize by donating electrons or hydrogen atoms. This measures both hydrophilic and lipophilic radical scavenging, making it ideal for plant extracts; activity is often expressed as Trolox equivalents.
(B) Bradford Method
Bradford assay uses Coomassie Brilliant Blue dye to bind proteins, causing a color shift for protein quantification via absorbance at 595 nm. It does not detect free radicals or antioxidants.
(C) Walkley and Black Method
This wet oxidation technique oxidizes organic carbon in soil with potassium dichromate and sulfuric acid, titrating excess dichromate to estimate soil organic matter. It targets carbon content, not radical scavenging.
(D) Kjeldahl Method
Kjeldahl digests samples with sulfuric acid to convert organic nitrogen to ammonium, followed by distillation and titration for total nitrogen/protein estimation. It is unrelated to antioxidants or free radicals.
The free radical scavenging activity of medicinal plant extracts plays a crucial role in evaluating their antioxidant potential, vital for pharmacology and GATE Life Sciences preparation. Among assays, the ABTS method stands out for precisely quantifying this activity in plant samples.
Understanding Free Radical Scavenging
Free radicals cause oxidative stress, and plant extracts rich in polyphenols scavenge them. Assays like ABTS detect this by monitoring radical neutralization, aiding medicinal plant research.
Why ABTS Method Excels
The ABTS (2,2′-azino-bis-(3-ethyl benzothiazoline-6-sulphonic acid)) assay generates a colored radical cation decolorized by extract antioxidants, measured at 734 nm. It suits both water- and fat-soluble compounds, yielding Trolox equivalents for standardization—perfect for medicinal plant extracts.
| Method | Purpose | Relevance to Free Radical Scavenging |
|---|---|---|
| ABTS | Antioxidant/radical scavenging | High – Direct radical decolorization |
| Bradford | Protein quantification | None – Dye-protein binding |
| Walkley-Black | Soil organic carbon | None – Carbon oxidation |
| Kjeldahl | Nitrogen/protein estimation | None – Digestion/titration |
Applications in Medicinal Plants
Studies on plants like Helicteres isora use ABTS to confirm high scavenging (e.g., 25,000+ μmol Trolox/g), validating therapeutic claims. For GATE aspirants, mastering ABTS distinguishes it from unrelated methods like Bradford.
This ABTS method for free radical scavenging activity ensures reliable, reproducible results in antioxidant screening.
