| dc.description.abstract | The work presented in this thesis has demonstrated that the use of elemental profiles for
the quality control of herbal medicines can be applied to multiple stages of processing. A
single method was developed for the elemental analysis of a variety of St John’s Wort
(Hypericum perforatum) preparations using Inductively Coupled Plasma – Optical Emission
Spectroscopy (ICP-OES). The optimised method consisted of using 5 ml of nitric acid and
microwave digestion reaching temperatures of 185⁰C. Using NIST Polish tea (NIST INCT-TL-
1) the method was found to be accurate and the matrix effect from selected St John’s Wort
(SJW) preparations was found to be ≤22%. The optimised method was then used to
determine the elemental profiles for a larger number of SJW preparations (raw herbs=22,
tablets=20 and capsules=12). Specifically, the method was used to determine the typical
concentrations of 25 elements (Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, In, Mg, Mn, Mo,
Ni, Pb, Pt, Sb, Se, Sr, V, Y and Zn) for each form of SJW which ranged from not detected to
200 mg/g. To further interpret the element profiles, Principal Component Analysis (PCA) was
carried out. This showed that different forms of SJW could be differentiated based on their
elemental profile and the SJW ingredient used (i.e. extract or raw herb) identified. The
differences in the profiles were likely due to two factors: (1) the addition of bulking agents
and (2) solvent extraction. In order to further understand how the elemental profile changes
when producing the extract from the raw plant, eight SJW herb samples were extracted
with four solvents (100% water, 60% ethanol, 80% ethanol and 100% ethanol) and analysed
for their element content. The results showed that the transfer of elements from the raw
herb to an extract was solvent and metal dependent. Generally the highest concentrations
of an element were extracted with 100% water, which decreased as the concentration of
ethanol increased. However, the transfer efficiency for the element Cu was highest with
60% ethanol. The solvents utilised in industry (60% and 80% ethanol) were found to
preconcentrate some elements; Cu (+119%), Mg (+93%), Ni (+183%) and Zn (+12%) were
found to preconcentrate in 60 %v/v ethanol extracts and Cu (+5%) and Ni (+30%). PCA of the
elemental profiles of the four types of extract showed that differentiation was observed
between the different solvents and as the ethanol concentration increased, the extracts
became more standardised. Analysis of the bioactive compounds rutin, hyperoside,
quercetin, hyperforin and adhyperforin followed by subsequent Correlation Analysis (CA) displayed relationships between the elemental profiles and the molecular profiles. For
example strong correlations were seen between hyperoside and Cr as well as Quercetin and
Fe. This shows potential for tuning elemental extractions for metal-bioactive compounds for
increased bioactivity and bioavailability; however further work in needed in this area. | en_US |
