| dc.description.abstract | Traditional Chinese Medicine (TCM) is one of the oldest medical systems in the world, still
used for prevention or treatment of diseases in the modern China. It is a unique and holistic
system, guided by ancient Chinese philosophy. The fish mint herb Houttuynia cordata Thunb
(Yu xing cao 鱼腥草) is widely used as a TCM herb in China for the treatment of ailments
including cancer, coughs, fever, dysentery, enteritis, and cognitive deficits. The H. cordata
medicine is used as a decoction prepared by traditional aqueous extraction of the dried plant
material, which is the most used formulation in TCM. Previous studies exploring organic
solvent extracts of H. cordata have been shown to contain secondary metabolites including
flavonoids, alkaloids, phenolics and volatile components. These extracts demonstrate anti-
inflammatory, anti-obesity, and anti-cancer effects as well as activity in inflammatory bowel
disease (IBD). However, there is a big gap in studies, with few investigations into the chemical
composition and biological activity of the H. cordata traditional aqueous decoction. Therefore,
research on the chemical fingerprinting and biological studies for H. cordata traditional
aqueous extract of is demanding.
In this thesis, sixteen H. cordata samples purchased from three different geographical regions
(Sichuan, Hubei, Anhui) in China were investigated. Plant identity for each material was
confirmed by microscopic means in comparison with monographs. Three extraction methods
(traditional aqueous decoction extraction, phytochemical extraction, and steam distillation) of
H. cordata were carried out. The chemically fingerprints for each extract were generated using
analytical techniques including Nuclear Magnetic Resonance (NMR) spectroscopy, High
Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) and Gas
Chromatography-Mass Spectrometry (GC-MS) as appropriate. The main focus of the study
was on the aqueous extract, which corresponds to the traditional medicinal decoction of H.
cordata. Principal component analysis (PCA) based on NMR spectroscopy metabolomics was
used to analyse the metabolomic data for the aqueous and phytochemical extracts, and this
allowed us compare small differences that become clearer in the metadata.
This project is centred on the traditional aqueous decoction, and biological activities of the
corresponding aqueous extracts were assessed and correlated with the chemistry. We initially
investigate the ability of the extracts to inhibit the cholinesterase enzymes including
acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The extracts only
demonstrated significant inhibition of AChE activity. The anti-inflammatory activity of
aqueous extracts was then evaluated in vitro (TNF-α activated Caco-2 monolayers) by
assessing intestinal inflammation associated mediators (ZO-1, Occludin, EGFR, IL-1β, IL-6,
IL-10, MAPK ERK 1/2) through RT-qPCR, ELISA and Western-blot. The anti-inflammatory
role of H. cordata was then further evaluated in a DSS-induced murine colitis model in vivo.
In this model both prevention and recovery effects of the H. cordata aqueous extract were
evaluated by disease scores (weight loss, bloody stool, diarrhoea), hematoxylin and eosin
staining of colonic tissue, and mediators associated with inflammation (MPO, Occludin, TNF-
α,EGFR, IL-1β, IL-6, IL-10).
Principal component analysis (PCA) of the 1H NMR spectroscopy metadata for the 16 samples
analysed distinguished three aqueous outliers. Three outliers were also distinguished between
the samples, from their phytochemical (MeOH) extracts. The outliers identified in the two types
of extract differed from each other, showing that the plants biosynthesis different chemical
metabolites depending on their area of cultivation and methods of preparation and storing.
Fifteen compounds were identified and quantified by HPLC-MS. Using this technique
qualitative and quantitative differences between the aqueous outliers and quality control (QC)
sample can be distinguished. Twenty-eight volatile compounds were identified by GC-MS in
the essential oil recovered by steam distillation of H. cordata plant material. The main
component identified in this oil is 2-undecanone known as the ‘fish mint’ marker. H. cordata
aqueous extracts showed protective effects on the intestinal inflammation in vitro by enhancing
ZO-1, Occludin, IL-10 and suppressing EGFR, IL-1β and IL-6. A mechanism explaining this
activity via an EGFR dependent MAPK (ERK) 1/2 signalling pathway is proposed. The three
chemically different aqueous outliers, are shown to be pharmacologically different, in these
biological studies. An international Good Manufacture Practice (GMP) standardised product
of H. cordata plant material from Hubei showed more potency. A beneficial intestinal
improvement observed in vivo, was seen at a molecular level within colonic tissues for both
the prevention and recovery trial, which agrees with in vitro findings, although no apparent
enhancement in recovery symptoms was observed.
In conclusion, aqueous extracts from H. cordata sourced from different geographical regions
have been shown to be chemically different, which may be a result of biotic and abiotic factors.
these observations underpin the need for scientific evaluation of TCM herbal material to
ensure its consistent quality, safety, and efficacy. Extracts were prepared using traditional
aqueous and phytochemical extraction methods. These extracts have different chemical
fingerprints. The resulting H. cordata aqueous decoctions also demonstrated varying intensity
of pharmacological activity. Inhibition of the enzyme AChE supports the use of H. cordata in
improving cognitive health and is worthy of further study. Confirmation of the role of the
traditional decoction of H. cordata in the support of intestinal barrier integrity is very
significant and validates the traditional use of H. cordata decoction in the treatment of
inflammatory gut conditions such as inflammatory bowel disease (IBD). | en |
