Isolation of Quercetin from "Allium cepa" Estimation of Total Phenolic and Flavonoid Content in Common Medicinal Plantas "Ficus benghalensis, Elaeocarpus sphaericus, Ipomea carnea and Azeratum conyzoides" and their Antioxidant Activities

Table of Contents

1. Introduction

1.1. Introduction

1.2. Objectives of study

1.3. Literature Survey

2. Experimental Section

2.1 Materials

2.2 Methods

3. Result and Discussion

3.1. Sohxlet Extraction of Outer Scale of Allium cepa

3.2. Test for Phenolic and Flavonoid Compounds

3.3. Liquid- liquid Extraction

3.4. Isolation of Quercetin

3.5. Characterization of Quercetin

3.6. Preparation of Extracts for the Estimation of Total Phenolic and Flavonoid Contents

3.7. Estimation of Total Phenolic Content (TPC)

3.8. Estimation of Total Flavonoid Content (TFC)

3.9. Determination of Antioxidant Activity

3.10. Correlation between DPPH Free Radical Scavenging Activity (IC50) and TPC

4. Conclusion

Research Objectives and Focus

This dissertation focuses on the isolation of quercetin from the outer scales of Allium cepa and the subsequent evaluation of total phenolic and flavonoid contents, alongside antioxidant activities, in four medicinal plants (Ficus benghalensis, Elaeocarpus sphaericus, Ipomea carnea, and Ageratum conyzoides) from Nepal, aiming to establish the correlation between phenolic concentration and antioxidant potential.

• Isolation and characterization of quercetin from Allium cepa.
• Comparative analysis of total phenolic and flavonoid content in selected medicinal plants.
• Evaluation of antioxidant activity using DPPH radical scavenging assays.
• Correlation studies between chemical composition and antioxidant efficacy.
• Investigation of extraction methods (methanol, 50% methanol, 70% acetone) on yield and antioxidant activity.

Excerpt from the Book

Summary of Chapters

1. Introduction: This chapter introduces natural products, specifically phenolic compounds and flavonoids, and outlines the objectives of the study including the isolation of quercetin and the screening of medicinal plants.

2. Experimental Section: Provides a detailed account of the materials, instruments, and methodological procedures used for plant extraction, phytochemical testing, and quantitative analysis.

3. Result and Discussion: Presents the findings regarding the isolation of quercetin from Allium cepa and discusses the quantitative results of phenolic/flavonoid contents and antioxidant assays for the selected plant species.

4. Conclusion: Summarizes the key findings of the research, confirming the presence of phenolic compounds and their correlation with antioxidant activities in the studied medicinal plants.

Keywords

Quercetin, Allium cepa, Ficus benghalensis, Elaeocarpus sphaericus, Ipomea carnea, Ageratum conyzoides, Antioxidant Activity, DPPH Assay, Total Phenolic Content, Total Flavonoid Content, Natural Products, Phytochemicals, Medicinal Plants, Solvent Extraction, Radical Scavenging.

Frequently Asked Questions

What is the primary scope of this dissertation?

The research primarily investigates the isolation of quercetin from onion scales and the quantitative assessment of phenolic and flavonoid content, as well as the antioxidant potential, of four specific medicinal plants from Nepal.

Which medicinal plants were studied in this research?

The study examines Ficus benghalensis, Elaeocarpus sphaericus, Ipomea carnea, and Ageratum conyzoides.

What is the main objective regarding quercetin?

The goal is to isolate and identify quercetin from Allium cepa to serve as a standard for calibration curves in the determination of flavonoid content in other plant extracts.

What analytical methods are utilized for the antioxidant assay?

The research employs the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay to evaluate the antioxidant activity of the plant extracts.

How is the total phenolic content determined?

Total phenolic content is estimated spectrophotometrically using the Folin-Ciocalteu reagent and is reported as Gallic Acid Equivalents (GAE).

What is the significance of the correlation study?

The correlation study links IC50 values (antioxidant capacity) to total phenolic content, indicating whether phenolic compounds are the primary contributors to the observed antioxidant activity.

What was the result of the quercetin isolation?

The isolation process yielded 51.6 mg of yellow powder, which was characterized through melting point determination and spectral analysis (UV and IR) as quercetin.

How do different extraction solvents affect the results?

The study found that the extraction yield and the content of phenolics and flavonoids varied significantly depending on the solvent used (methanol, 50% aqueous methanol, or 70% aqueous acetone).

Which plant showed the highest total phenolic content?

The 70% aqueous acetone extract of Elaeocarpus sphaericus exhibited the highest detected amount of phenolic compounds.

What is the conclusion regarding the correlation coefficient?

The research found a strong linear correlation between total phenolic content and antioxidant activity, yielding an R² value of 0.931.