Abstract
Historically, plants have been used as nutraceuticals owing to the presence of a vast array of
bioactive compounds (metabolites/natural products). These bioactive molecules are reported
to exhibit a variety of beneficial biological activities and with potentials to be used in various
applications including medicine, drug design, agrochemicals and biopesticides. Recently,
there has been a growing interest in the therapeutic value of underutilized herbal plants
which are normally considered as wild plants or weeds. These plants have been reported to
possess biologically active metabolites such as phenolic compounds. However, there is a lack
of scientific studies to substantiate these beneficial claims, and to contribute in
comprehensive phytochemical descriptions of these plants. It is to be noted that the
differential distribution of metabolite patterns in different parts of the plant is highly
regulated and, as such, comprehensive studies aimed at analyses of total metabolite
composition in all these parts are thus imperative. Furthermore, the understanding of the
metabolic compositions of these plants does not only contribute towards the nutraceutical
attributes but can be further exploited for their other purposes such as chemotaxonomy.
Thus, in the current study, a comprehensive phytochemical characterization of an
underutilised plant, Sonchus oleraceus was investigated using the liquid chromatography
mass spectrometry (LC-MS) based metabolomics approach. The studied metabolite
composition namely, chicoric acid of S. oleraceus was from leaf, stem and roots. Furthermore,
a comparative LC-MS-based metabolomics approach was applied to establish the
chemotaxonomic correlation of S. oleraceus to other selected underutilised green leafy
vegetable plants from the Asteraceae plants (Bidens pilosa and Vernonia fastigiata). Based on
the chemotaxonomy results, chicoric acid found in S. oleraceus and B. pilosa were found to
have a different elution profile and thus different bioactivity. Therefore, the discrimination of
stereoisomers of chicoric acid found in S. oleraceus and B. pilosa leaves was also undertaken
using ultraviolet (UV) irradiation, LC-MS, density functional theory (DFT) models and
molecular docking.
The results obtained revealed that S. oleraceus has a myriad spectrum of secondary
metabolites including flavonoids, hydroxycinnamic acids and sesquiterpenes...
M.Tech. (Biotechnology)