Abstract |
Τhis dissertation uses NMR-based metabolomics and chemometric methods for the
analysis of several extracts of plant origin (olive oil mill water condensates, spearmint
extracts, olive leaves) and biological fluids (culture media, rat urine and human blood
plasma).
A novel spectroscopic “standardless” analytical NMR methodology that does not
necessitate the use of an internal quantification standard, qEretic2, was developed and
validated for the quantification of olive leaf metabolites. This methodology was
applied for the metabolite/phenolic profiling of olive leaves obtained from trees of
two different cultivars (Picual, Koroneiki) as a function of leaf harvest time, resulting
in the successful classification of leaves of different cultivar, while harvest time was
found to also have an effect on the phenolic content of the leaves.
The qualitative and quantitative characterization of olive oil mill water condensates
and spearmint extracts by NMR spectroscopy was conducted in order to aid their use
as phenolic antioxidant additives in functional foods. NMR analysis showed that plant
origin and year of production have a significant effect on the type and quantity of
bioactive and phenolic compounds present in these plant-derived extracts.
The effect of olive oil mill water condensates and spearmint extracts as encapsulated
antioxidant additives of functional foods on metabolism was studied in three separate
studies (a) HepG2 cell cultures during cell growth, (b) an animal model utilizing the
NMR-based urine analysis after acute administration of encapsulated extracts in high
fat-fed rats, and (c) two clinical studies using healthy volunteers that adhered to a
specific diet that included administration of microencapsulated extracts in functional
foods (pariza, meat product containing an olive oil mill water condensate and yoghurt
containing a spearmint extract).
Multivariate statistical model analysis demonstrated the temporal changes in the
metabolite profile of rat urine and the effect of bioactive compounds present in the
two plant extracts. The analysis of the metabolite and blood plasma lipid profile of
healthy volunteers demonstrated an extract type-dependant metabolic effect of the encapsulated components of the functional foods, in agreement with clinical
biochemical blood markers (glucose, LDL-HDL cholesterol). The metabolic effect
due to the consumption of the functional food was more pronounced in volunteers
with at least two biochemical or anthropometric elements of cardio-metabolic risk.
Finally, the NMR-obtained metabolite dataset was analysed using Metaboanalyst 3.0
in order to elucidate the metabolic pathways involved in the metabolite profile
changes observed during the cell culture media, animal model and healthy volunteer
studies. It was found that similar metabolic pathways were involved in all three cases
after administration of the same plant-derived extract.
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