Exploiting Traditional Chinese Medicine for Potential Anti-Microbial Drug Leads

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Student thesis: Doctoral ThesisDoctor of Philosophy

Original languageEnglish
Awarding Institution
Award date30 Jan 2021
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Over the past few years, natural products have already become increasingly important in antiinfectious drug research. This is especially the case as innovations in omics’ technologies, chemical biology and genetics have facilitated the discovery of new drugs and their targets. Natural products have a privileged role in the drug discovery due to their intrinsic cell permeability, structural diversity, rich functionality and stereochemistry. They also provide unique scaffolds for further drug optimization towards increased potency and selectivity. China has been using herbs in medicine for centuries and these are now attracting global interest. In response to the challenge of increased anti-microbial resistance our group established a ChinaUK collaborative team to explore the potential of Traditional Chinese Medicines (TCM) to reveal new drug leads. This project focuses on 19 traditional Chinese herbs which were screened for a bioactives using a well-established analysis pipeline. All the plants were provided from China and underwent authentication using DNA barcoding and bioactivity screening of the extracts, mainly focusing on anti-microbial activities. Based on rbcl based DNA barcoding data some samples were misidentified in China whilst some samples of the same species exhibited differences in minimum inhibitory concentrations (MIC). The initial focus was on an assay-based evaluation of isolated compounds from Artemisia annua against mycobacteria. Artemisia annua is native to temperate Asia, known have antimalarial, anti-inflammatory, antitumor and allelopathic activities. Natural products with relatively weak anti-mycobacterial activity with MIC of 250 µg/mL from Artemisia annua were found with. Several fractions, isolated using different chromatography techniques, showed very significant anti-tubercular activity against M. smegmatis. Purification, isolation and identification of two compounds (artemisinic acid and deoxyartemisinin) using various chromatography techniques and identification using high-resolution mass spectrometry and nuclear magnetic resonance (NMR) with the best activity have been performed along with toxicity assays and Schistosoma mansoni assays. The mode of action using computerpredicting docking with other known targets of M. tuberculosis. Based on the MIC pattern and docking algorithms it was predicted that artemisinic acid could probably target KasA protein of Mycobacterium. Next the antimicrobial properties of herbs, Dryopteris crassirhizoma Nakai were identified as potential drug lead against Methicillin-resistant Staphylococcus aureus (MRSA). Bioactive phloroglucinols from D. crassirhizoma were isolated, purified, and identified using a range of bioactivity screens coupled with chromatographic and metabolomics approaches. The antimicrobial properties of the extracts and fractions yielded MIC ranging from 3.25-50 µg/mL. The potential compounds responsible for MIC were tentatively identified through metabolite fingerprinting using flow infusion electrospray high-resolution mass spectrometry (FIE-HRMS). Additionally, the mode of action of the selected fractions was suggested using non-targeted metabolomics analysis with other known antibiotics and docking with known targets. Metabolomics data shows that the anti-MRSA activity was linked to the altered carbohydrate metabolism that could reflect the inhibition of growth of the cells. This study requires further validation for the compounds from D. crassirhizoma using genomics, proteomic, and lipidomic analyses and in silico studies. Overall, our study can help find different naturally available compound and help in the identification of targets to fight different diseases including the drug resistant disease.