Antimicrobial Activity of Ethnobotanically Selected Plant Extracts Against Porphyromonas gingivalis Open Access

Carrol, Danielle (Spring 2020)

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Porphyromonas gingivalis is the keystone pathogen of periodontitis, a chronic inflammatory disease which causes tooth loss and deterioration of gingiva, alveolar bone, and periodontal ligaments. This bacteria has been linked to a number of peripheral and neurological diseases, including cardiovascular disease, diabetes mellitus, respiratory infection, rheumatoid arthritis, osteoporosis, obesity, pre-term birth, depression, and Alzheimer’s disease. P. gingivalis interacts with the brain directly via secreted proteases which enter the brain, induce inflammation, and directly affect β-Amyloid and tau proteins. Given how widespread periodontal disease is (greater than 70% of adults over 65 are affected), its range of damaging properties, and growing resistance to many antibiotics, finding new methods of inhibiting P. gingivalis growth is paramount. The ethnobotanical approach to drug discovery offers a promising method of discovering new compounds to combat P. gingivalis while also addressing the growing problem of antibiotic resistance. In this study, a review of plant medicines used for oral hygiene or symptoms of periodontitis was conducted. From the resulting database of 513 plants, 30 plants were tested against P. gingivalis, and 11 of these plants demonstrated high growth inhibition, verifying their traditional medicinal uses. Minimum inhibitory concentration as well as cytotoxicity against human keratinocytes was determined for each of these plant extracts. Promising therapeutic indices for these 11 plants supports further testing including biofilm eradication and bioactivity guided fractionation and potential development as antibiotic pharmaceuticals or additives to oral hygiene products.

Table of Contents

Table of Contents


Chapter 1: Introduction: Overview 9

Porpyromonas gingivalis  – mechanisms of infection and evading host immune response 9

Antibiotic Resistance and the Search for New Antimicrobials 9

Ethnobotanical Approach to Drug Discovery 10

Specific Research Question and Project Aims 11

Chapter 2: Introduction: Porphyromonas gingivalis and the Brain 12

The inflammatory connection to AD 12

P. gingivalis causes increased inflammatory load and interacts directly with key AD pathologies 13

Chapter 3: Materials and Methods 14

Literature Review of Oral Health Related Plants   14

Bacterial Strains and Growth Conditions 14

Colony Counting to determine CFU/mL 15

Single Concentration Screens 15

Minimum Inhibitory Concentration Assays 16

Cytotoxicity Assay 16

Chapter 4: Results 18

Literature Review of Oral Health Related Plants 18

Single Concentration Screens 19

MIC Assay 22

Cytotoxicity Assay 22

Chapter 5: Discussion 26

Supplementary Materials 38

Protocol Design 38

Oral Health Related Plants Review 44

Single Concentration Screen Full Results 92


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