Directing Biosynthesis of Bioactive Triterpenes for Pharmaceutical Applications

Casson, Rebecca (2022) Directing Biosynthesis of Bioactive Triterpenes for Pharmaceutical Applications. Doctoral thesis, University of East Anglia.

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Abstract

Triterpenes are a large, structurally diverse class of plant specialised metabolites, with a history of use as components of traditional medicine, and potential as a source of therapeutics for the treatment of cancer and inflammatory diseases. The development of triterpene-based therapeutics would be greatly aided by a systematic structure-activity relationship investigation, requiring the procurement of a suite of structurally related molecules for investigation. However, the low abundance of triterpenes in nature and their recalcitrance to chemical synthesis presents a challenge. Recent understanding of triterpene biosynthesis in heterologous hosts provides a promising new platform to produce specific triterpenes for evaluation, overcoming these problems.

In this thesis, the triterpene toolkit developed in the Osbourn lab is used to produce a range of triterpenes in N. benthamiana. Novel putative triterpenes are generated through combination of toolkit enzymes (Chapter 3). Expansion of the toolkit allows for the identification of new functionalities on the β-amyrin scaffold (Chapter 4). Large-scale production allows for structural determination of a suite of triterpenes with a range of regio- and stereo-chemistries (Chapter 5). These are evaluated for anti-proliferative and anti-inflammatory effects (Chapter 6). A detailed structure-activity relationship investigation is carried out, and methods for improving the throughput of triterpene biological testing are considered (Chapter 7).

Key findings include the production of 64 triterpenes through combinatorial biosynthesis, including 31 novel structures, the expansion of the triterpene toolkit to include bacterial and human cytochromes P450, the generation and purification of a suite of 20 β-amyrin derivatives (14 of which were fully structurally verified by NMR), the discovery of three new positions on the β-amyrin scaffold responsible for anti-proliferative activity, and three triterpenes with anti-inflammatory activity. A structure-activity relationship investigation also predicts novel bioactive triterpenes. This work will provide the basis for the design of triterpenes optimised for improved biological activity.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	12 Jun 2023 12:36
Last Modified:	31 Jan 2024 01:38
URI:	https://ueaeprints.uea.ac.uk/id/eprint/92359
DOI:

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