Superoxide Anion Content Assay Kit (Sulfanilamide, Colorimetric Method)

Cat. No.: S1508296

GRADE & PURITY BioReagent

Overview

The superoxide anion radical, a type of free radical produced during organism metabolism, can attack biological macromolecules such as lipids, proteins, nucleic acids, and polyunsaturated fatty acids, causing cross-linking or fragmentation, and damaging cellular structure and function. It is closely related to aging and pathological conditions, and research into scavenging superoxide anion radicals has garnered widespread attention. Molecular oxygen in organisms can undergo single‑electron reduction to form the superoxide anion radical (O₂⁻). O₂⁻ can directly act on macromolecules like proteins and nucleic acids, and can also generate reactive oxygen species such as hydroxyl radicals, singlet oxygen, hydrogen peroxide, and lipid peroxide radicals, which are damaging to cellular structure and function.

Detection Principle

Under acidic conditions, two molecules of O₂⁻ react with hydroxylamine to produce one molecule of NO₂⁻. NO₂⁻ then reacts with sulfanilic acid and naphthylamine to form a pink azo compound. The absorbance at 530 nm is measured using a spectrophotometer. Within a certain range, the color intensity is proportional to the O₂⁻ concentration. Based on the A₅₃₀ value and the stoichiometric relationship between NO₂⁻ and O₂⁻ in the relevant reactions, the concentration of O₂⁻ in the sample can be calculated. This method is primarily used to determine the content or production rate of superoxide anion radicals in plant tissues.

S1508296	Component	50T	Storage
S1508296A	NO₂⁻ Standard (1 mM)	1 mL	2-8℃. Store in the dark.
S1508296B	O₂⁻ Lysis Buffer	125 mL	RT.
S1508296C	Hydroxylamine Solution	30 mL	2-8℃.
S1508296D	Sulfanilic Acid Color Development Solution	30 mL	2-8℃. Store in the dark.
S1508296E	Naphthylamine Color Development Solution	30 mL	2-8℃. Store in the dark.

Reagents, consumables and Equipments not provided

• Spectrophotometer (capable of measuring absorbance at 530 nm)
• Mortar or homogenizer, Low‑temperature centrifuge, Incubator or water bath
• Centrifuge tubes or test tubes, Cuvette
• Distilled water, etc.

Procedure

1. Sample Preparation

1.1 Plant Samples

Take fresh plant tissue (normal or under stress), wash clean, dry, cut into small pieces, and quickly weigh 1–1.5 g. Add 2 mL of pre‑chilled O₂⁻ Lysis Buffer and homogenize or grind on ice. Centrifuge at 4°C, 10,000 g for 10 minutes. The supernatant is the superoxide anion radical extract. Store at 4°C for use.

1.2 Plasma, Serum, and Urine Samples

Plasma and serum prepared by standard methods can be directly used for assay with this kit. Store at 4°C for detection of superoxide anion radicals.

1.3 High‑Activity Samples

If the sample contains a high concentration of superoxide anion radicals, dilute appropriately with O₂⁻ Lysis Buffer.

2. Preparation of Series NO₂⁻ Standard Solutions

Bring the NO₂⁻ Standard (1 mM) to room temperature, then continue dilution according to the table below:

Additive (mL)	Std.1	Std.2	Std.3	Std.4	Std.5	Std.6
NO₂⁻ Standard (1 mM)	0.01	0.02	0.03	0.04	0.05	0.06
Distilled Water	0.99	0.98	0.97	0.96	0.95	0.94
NO₂⁻ Content (μM)	10	20	30	40	50	60

3. O₂⁻ Sample Loading

Set up blank, standard, and test tubes according to the table below. Add solutions in the specified order, avoiding bubble formation. If the superoxide anion radical concentration in the sample is too high, reduce the sample volume or dilute appropriately before measurement. It is best to set up replicate tubes for each sample.

Additive (mL)	Blank Tube	Standard Tube	Test Tube
Distilled Water	1	—	—
Series NO₂⁻ Standards (No. 1–6)	—	1	—
Test Sample	—	—	0.25
O₂⁻ Lysis Buffer	—	—	0.25
Hydroxylamine Solution	—	—	0.5

Mix well and incubate in a 25°C water bath for 20 min.

Sulfanilic Acid Color Development Solution	0.5	0.5	0.5
Naphthylamine Color Development Solution	0.5	0.5	0.5

Mix well and incubate in a 30°C water bath for 30 min.

4. O₂⁻ Assay

Zero the instrument with the blank. Using a cuvette with a 1 cm light path, measure the absorbance at 530 nm for the standard and test tubes using a spectrophotometer (recorded as A_Standard and A_Test).

5. Calculation of Results

Plot a standard curve using the series NO₂⁻ standard contents (μM) from tubes 1–6 as the x‑axis and the corresponding absorbance as the y‑axis. Calculate the NO₂⁻ content based on the absorbance of the test tube. Calculate the superoxide anion radical (O₂⁻) content in the specific sample using the following formulas:

For plant tissue samples:

O₂⁻ (μM/g) = 2 × n × V_T / (W × V_S)

For serum, urine, and other liquid samples:

O₂⁻ (μM/mL) = 2 × n × N / V_S

Definition of Superoxide Anion Production Rate: The amount of superoxide anion produced per minute per gram of fresh tissue weight. Calculation formula:

Superoxide Anion Production Rate [μmol/(min·g)] = 2 × n × V_T / (W × t × V_S)

After measuring the protein content in the sample, the following formula can be used:

Superoxide Anion Production Rate [μmol/(min·mg)] = 2 × n × V_T / (m × t × V_S)

Parameter Description:

2: Stoichiometric coefficient between NO₂⁻ and O₂⁻

n: NO₂⁻ content obtained from the standard curve (μM)

V_T: Total volume of superoxide anion radical extract (mL)

N: Sample dilution factor

W: Sample fresh weight (g)

m: Protein content in the sample (mg)

t: Reaction time between sample and hydroxylamine (min) = 20

V_S: Volume of extract added during measurement (mL)

Notes

1. Experimental materials should be as fresh as possible. If not used immediately after collection, store at 4°C.

2. If the sample contains a high amount of chlorophyll, which may interfere with the assay, extract chlorophyll with an equal volume of ether or chloroform after incubation with hydroxylamine solution at 25°C for 20 minutes, then proceed with the color development reaction.

3. If a spectrophotometer is not available, a standard microplate reader can be used, but the maximum detection volume of the microplate reader should be considered.

4. If the measured sample concentration is too high, dilute the sample with O₂⁻ Lysis Buffer and repeat the assay.

5. Sulfanilic Acid Color Development Solution and Naphthylamine Color Development Solution are highly irritating. Operate in a well‑ventilated area and tighten bottle caps after use to avoid evaporation.

6. Use reagents as soon as possible after opening to avoid affecting subsequent experimental results.

7. This kit is intended for research use only and is not suitable for clinical diagnosis or other purposes.

Storage and Shipping

Storage

Store at 2-8°C,Protected from light,Room temperature

Shipped In

Wet ice

Stability And Storage

Each component has a shelf life of 1 year under corresponding storage conditions. S1508296A, S1508296D, S1508296E: Store at 2-8℃ long term (12 months). Store in the dark. S1508296B: Store at room temperature long term (12 months). S1508296C: Store at 2-8℃

Contents & Storage

S1508296	Component	50T	Storage
S1508296A	NO₂⁻ Standard (1 mM)	1 mL	2-8℃. Store in the dark.
S1508296B	O₂⁻ Lysis Buffer	125 mL	RT.
S1508296C	Hydroxylamine Solution	30 mL	2-8℃.
S1508296D	Sulfanilic Acid Color Development Solution	30 mL	2-8℃. Store in the dark.
S1508296E	Naphthylamine Color Development Solution	30 mL	2-8℃. Store in the dark.