Lecture 5.4 (TCM) Flashcards
What is TCM?
Traditional Chinese Medicine
What are some examples of alternate medicine?
chiropractic, herbal therapy, traditional Chinese medicine (TCM), meditation, yoga, acupuncture, and diet- based therapies.
TCM has a long history of use in China with a proven record of high efficacy and low toxicity. Therefore, the use of empirical knowledge is an advantage over other screening strategies.
True or False
True
Why use ‘knowledge based approach’ for TCMs?
TCM can be considered as a collection of “screened” natural products
Describe construction of TCM-based sample libraries.
- Select TCM based on empirical knowledge and available scientific data
- construct a TCM-based sample library composed of formulae, crude extracts, active fractions, and pure compounds.
- Develop and explore combinatorial libraries
In how many categories does NMPA classify TCM into?
9
What does category 1 of NMPA’s TCM classification refer to?
active component isolated and extracted from plants, animals, or minerals and its preparation (content of active component in the product > 90%) that have not been marketed in the domestic market previously.
What does category 9 of NMPA’s TCM classification refer to?
generic drugs
What do the categories of NMPA’s TCM classification (except for cat 1 and 9) entail?
technology innovation (e.g., optimization of dosage form and drug delivery methods) or
new discoveries (e.g., new active constituents, new plant parts for medicinal application, etc.)
Previously, how were botanical products marketed?
as conventional food and dietary supplements with health-related claims.
Under what circumstance is a botanical product considered a drug?
if it bears a disease claim.
For a botanical product to be marketed as a drug, what requirements must the botanical drug meet?
the regulatory requirements for safety and effectiveness and comply with the manufacturing requirements to ensure product quality.
What are the top 3 therapeutic categories for botanical drug products in the US?
- oncology
- endocrine metabolic
- rheumatological analgesic
What is a typical workflow for the generation of NP sample library?
solvent extraction of raw material
—-> organic extract + aqueous extract
——> fractionation
———> parellel multiple channel preparative HPLC
*activity screening can be performed after solvent extraction, at any of the steps
What is the chemical process for NP-based drug discovery?
- The NP is extracted, concentrated, fractionated and purified to yield biologically active compounds
- identification of known compounds to avoid replication of previous effort
- unknown structures determination thru high resolution NMR, MS, UV, IR
- preliminary SAR studies
- scale of of purification process
- synthetic modification –> potential lead from ‘hit’
- development of track candidate thru additional optimisation
What is bio-assay guided fractionation?
starting with the extraction of natural materials of interest using organic solvents such as alcohol. –>
tested as crude extracts –>
isolation and identification of active compounds
How to check purity of compound?
LC or LCMS
What techniques are used to determine the structure of an unknown active compound?
NMR, MS, UV, IR, X-ray diffraction, optical rotatory dispersion (ORD), circular dichroism (CD)
What are the key technologies in NP research?
- Natural product databases + structure determination technologies –> identification of known compounds
- extraction/isolation technologies –> bioassay guided fractionation
- structure determination technologies
Give some examples of extraction/isolation technologies
- Supercritical Fluid Extraction (SFE)
- Accelerated Solvent Extraction (ASE)
- Pressurized Liquid Extraction (PLE)
- Microwave-assisted Extraction (MAE)
- Liquid – solid Isolation Technologies
—> LC with solid absorbent as stationary phase - Liquid-liquid Isolation Technologies:
—> Counter-current Chromatography (CCC) - gas chromatography
What systems can HPLC coupled to for structure determination?
MS, NMR, CD
Describe a HPLC-based identification system.
affinity selection –> second column for resolving into single components –> structure info by online UV, MS and NMR
What kind of info does MS and NMR provide?
MS –> fragment ions
NMR –> substructure i.e. more extensive structural info
What is directed biosynthesis?
Manipulate the genes associated with biosynthetic pathways to allow the engineering of compounds of interest.
What is the genomic mining approach?
rapid ID of gene clusters that encode bioactive natural
products –> allows computer predictions of chemical structure based on the sequence info
Apart from conventional approaches in identifying the structure of NP or biological products, what technique could be used?
Genomic mining approach
What is combinatorial biosynthesis (CB) and how can it complement the traditional chemical modification methodologies?
- introduce new functional groups onto natural product scaffolds
- uses ‘tailoring’ enzymes in combinatorial approaches to expand natural product diversity
HOWEVER, may not be applicable to synthetic compounds
Combinatorial Biosynthesis (CB) is unique to natural products and may not be applicable to the modification of synthetic compounds.
True or False
True
Combinatorial Biosynthesis (CB) uses ‘tailoring’ enzymes, give some examples of tailoring reactions.
glycosylation, oxidation and reduction, methylation, halogenation, acylation and sulfation.
A powerful approach to discover novel metabolites is to access sources of organisms that have not been explored previously.
True or False
True
What are some unexplored sources that could be used to discover novel metabolites?
- microbes
- marine environment microorganisms
What are some microorganisms from the marine environment that will provide a high chance of finding novel drugs from natural sources?
actinomycetes
fungi
mycobacteria
What are some obstacles in NP-based drug screening?
- not possible to culture organism out of habitat
- relevant NP not produced when organism out of habitat
- presence of NPs that are known
- presence of NPs that do not have drug-like property
- bioactive NPs present in insufficient amounts
- unknown molecular targets for NPS IDed with phenotypic assays
What could be done to maximise the diversity of extracted NPs?
The biological material can be subjected to extraction with several solvents of different polarity.
What are some solutions for overcoming obstacles in NP-based drug screening?
new methods for dereliction, extraction and pre-fractionation of extracts to eliminate false positives/interfering agents
How to overcome the problem of the lack of possibility to culture the organism out of the natural habitat?
new methods for culturing and in situ analysis
How to overcome the problem of ‘relevant NP not produced when organism out of habitat’?
- new methods for culturing and in situ analysis
- new methods for NP synthesis induction and heterologous expression of biosynthetic genes
How to overcome the problem of ‘presence of NPs that are known’?
new methods for dereplication
How to overcome the problem of ‘presence of NPs that do not have drug-like property’ and ‘bioactive NPs present in insufficient amounts’?
New methods for extraction and pre-fractionation of extracts
What does genome mining- based approaches to explore the biosynthetic capacity of microorganisms rely on?
DNA extraction, sequencing and bioinformatics analysis
What is heterologous expression?
Heterologous expression is the introduction of either complementary DNA (cDNA) or RNA (cRNA) encoding for a protein of interest from one species into the cell of another species, such that the hosts’ cellular machinery expresses the foreign protein
What are the steps in genome mining-driven discovery of NPs?
- DNA isolation from specific micorganism
- sequencing
- bioinformatic analysis
4a. heterologous expression –> NP isolation/characterization OR
4b. NP chemical synthesis OR
4c genetic manipulation of the native host –> NP isolation /characterisation
What is the strength of ‘synthetic-bioinformatic’ approach?
it is entirely independent of microbial culture and gene expression
What are the limitations of ‘synthetic-bioinformatic’ approach?
- accuracy of computational chemical structure predictions
- feasibility of total chemical synthesis
Unmodified NPs often possess suboptimal properties, and superior analogues need to be obtained in order to yield valuable new drugs.
True or false
True
Unmodified NPs often possess suboptimal properties, and superior analogues need to be obtained in order to yield valuable new drugs.
How can NP analogues be obtained?
- Total chemical synthesis followed by chemical derivatization
- Semisynthesis using a NP as a starting point
- Biosynthetic engineering using manipulations of biosynthetic pathways of the producing organism to generate NP analogues
Natural Product – based Drug Discovery is :
A multidisciplinary approach, involving the generation of truly novel molecular diversity from natural product sources, combined with total and combinatorial synthetic methodologies, and including the manipulation of biosynthetic pathways, provides the best solution to the current productivity crisis facing the industry and scientific community engaged in drug discovery and development.
