Mengukur Antioksidan Metode DPPH

Summary

In this video, the DPPH method is explained for measuring the antioxidant activity in plant extracts, specifically tea leaves. Antioxidants work by donating electrons to free radicals like DPPH, changing its purple color to yellow. The process involves preparing extracts at varying concentrations, mixing them with DPPH, and measuring absorbance at 517 nm. The results show that higher concentrations of tea extracts exhibit stronger antioxidant activity, with an IC50 value of 1983 PPM, indicating substantial antioxidant potential. The method serves as an accessible approach to studying antioxidant properties in plant-based substances.

Takeaways

• 😀 Antioxidants are molecules that can prevent the oxidation of other molecules by donating electrons to free radicals.
• 😀 A free radical example is DPPH (2,2-diphenyl-1-picrylhydrazyl), which reacts with antioxidants, changing color from purple to yellow when it receives electrons.
• 😀 Free radicals are produced in the body, but excessive amounts can damage cells, which antioxidants can help prevent.
• 😀 Common foods rich in antioxidants include tea, which contains phenolic compounds like catechins and epicatechins.
• 😀 The DPPH method is used to measure antioxidants by observing the color change as DPPH is reduced by antioxidant compounds.
• 😀 Tea leaves with different concentrations (500, 250, 150, 6, 2.5 PPM) are tested using the DPPH method to measure antioxidant activity.
• 😀 To measure antioxidant activity, tea extract is mixed with DPPH solution and incubated for 30 minutes in darkness before measuring absorption at 517 nm.
• 😀 A blank sample is used to calibrate the measurements, and only methanol is used in the blank, not the tea extract.
• 😀 The antioxidant value is calculated as the percentage of inhibition using the formula: ((Absorbance blank - Absorbance sample) / Absorbance blank) * 100.
• 😀 Higher concentrations of tea extract show higher antioxidant activity, with the IC50 value calculated using linear regression to determine the concentration needed to inhibit 50% of the activity.
• 😀 The antioxidant activity of the tea leaf extract is categorized as strong, with an IC50 value of 1983 PPM, indicating effective antioxidant properties.

Q & A

What are antioxidants and how do they work?

Antioxidants are molecules that inhibit the oxidation process of other molecules. They work by donating one or more electrons to free radicals, neutralizing their damaging effects.

What is DPPH, and how is it used in antioxidant measurement?

DPPH (2,2-diphenyl-1-picrylhydrazyl) is a stable free radical that reacts with antioxidants. When antioxidants donate electrons to DPPH, its violet or purple color changes to yellow, indicating the antioxidant activity.

How does excessive free radical production affect the body?

Excessive production of free radicals can damage cells, leading to oxidative stress, which is linked to various health issues like inflammation, aging, and chronic diseases.

What role does gallic acid play in the DPPH method?

Gallic acid acts as an antioxidant in the DPPH assay by donating electrons to DPPH, causing the radical to change from purple to a yellow or bright color, which indicates the inhibition of free radicals.

What is the relationship between phenolic compounds and antioxidants?

Phenolic compounds, such as catechins and epicatechins in tea, are responsible for antioxidant activity. These compounds help neutralize free radicals and protect cells from oxidative damage.

How is the concentration of antioxidants measured in tea extracts?

The concentration of antioxidants in tea extracts is measured using the DPPH assay. The absorbance of the solution is read at a wavelength of 517 nm, and the antioxidant value is calculated based on the change in color from purple to yellow.

What is the significance of the blank sample in the DPPH assay?

The blank sample contains only methanol and serves as a reference for measuring the absorbance of the sample. This helps in calculating the antioxidant activity by comparing the absorbance of the blank with that of the sample.

How are the results of the DPPH assay expressed?

The results are expressed as a percentage of antioxidant activity, calculated using the formula: [(Absorbance of blank - Absorbance of sample) / Absorbance of blank] * 100.

What does a lower antioxidant concentration mean in terms of absorption?

A lower concentration of antioxidants results in higher absorbance, indicating less inhibition of the DPPH free radical, meaning the antioxidant activity is weaker.

How is the IC50 value calculated, and what does it indicate?

The IC50 value is the concentration of a compound needed to inhibit 50% of free radical activity. It is calculated using a linear regression of antioxidant activity versus concentration. A lower IC50 value indicates stronger antioxidant activity.