Inhibition of Cytochrome P450 Isoforms by Ethanolic Extracts of Cinnamomum spp. (Lauraceae) Restricted; Files Only

Menkart, Matthew (Spring 2023)

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Herbal medicine is a key component of both traditional and Western medicines, but many herbs lack sufficient research on their ability to inhibit or induce cytochrome P450 enzymes (CYPs). Usage in conjunction with FDA-approved medication may lead to drug-herb interactions and potentially cause the accumulation of toxic metabolites, or other dangerous side effects. One of the most used traditional herbal medicines, Cinnamon (Cinnamomum spp.), was found to possess CYP inhibitory activity through prior high-throughput screening efforts. These studies aimed to determine species variation in CYP inhibition by C. species and identify which CYP isoforms are most affected. Five isoforms, CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A5, were tested against crude ethanolic extracts of four Cinnamomum species: C. burmannii, C. verum, C. cassia, and C. camphora. Extracts were prepared at concentrations ranging from 2 µg/mL to 64 µg/mL and inhibition was quantified using a half-maximal inhibitory concentration value. The greatest inhibition was observed in CYP2C9, with C. burmannii and C. verum being more inhibitory than C. cassia and C. camphora. This trend was seen across CYP2B6 and CYP3A5, CYP2C19 was most inhibited by C. camphora, while CYP2D6 showed negligible inhibition by the Cinnamomum extracts. Subsequent liquid-liquid partitioning and fractionation via reverse-phase high-performance liquid chromatography of C. burmannii suggest that inhibition of CYP2C9 may be attributed to only a few, non-polar phytochemicals. These results suggest that cinnamon has the ability to inhibit multiple CYP isoforms, but the extent of their inhibition varies across species, with C. burmannii and C. verum being the most inhibitory.

Table of Contents

Chapter 1: Introduction

1.1 Botanical Medicine and Herbal Supplements

1.2 Drug Metabolism

1.3 The Cytochrome P450 System

1.4 Drug-Herb Interactions

1.5 Project Aims

Chapter 2: Background

2.1 The Lauraceae Family and Cinnamomum

2.2 Previous Screening of the Quave Natural Products Library

2.3 Literature Review and Selection of Cinnamomum Genus

2.4 Cinnamomum burmannii

Chapter 3: Materials and Methods

3.1 Collection and Processing

3.2 Creation of the Extract Library

3.3 Initial Screening and CYP-Inhibition Assay

3.4 Bioassay Guided Fractionation

3.5 Dose-Response CYP-Inhibition Assay

3.6 Preparation of Partitions and Single-Dose CYP-Inhibition Assay Testing

3.7 Analytical and Preparatory Reverse Phase-High Performance Liquid Chromatography

Chapter 4: Results

4.1 Fractionation Scheme

4.2 Inhibitory Activity of Crude Cinnamomum Extracts

4.3 Chemical Composition of Crude Extracts

4.4 Inhibitory Activity of Cinnamomum Partitions and Analysis

4.5 Fractionation of 2017C and Inhibitory Activity

4.6 Fractionation of 2017C-PF7

Chapter 5: Discussion

5.1 Summary

5.2 Implications

5.3 Future Studies


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