Dissertation committee:
Καθηγητής Σκαλτσούνης Αλέξιος-Λέανδρος, Αναπληρώτρια Καθηγήτρια Μητάκου Σοφία, Επίκουρος Καθηγητής Νεκτάριος Αληγιάννης, Καθηγητής Βασίλειος Ρούσσης, Καθηγητής Εμμανουήλ Μικρός,Καθηγητής Δημήτριος Κουρέτας, Λέκτορας Δημήτριος Στάγκος
Original Title:
Φαρμακογνωστική μελέτη φυτών της οικογένειας Fabaceae (Vicia faba, Lotus edulis, Lotus longisiliquosus, Tetragonolobus purpureus, Lathyrus laxiflorus subsp laxiflorus) και του είδους Oryza sativa της οικογένειας Gramineae
Summary:
The aim of the present thesis was the detection and study of plants of the
Greek flora which showed significant antioxidant activity as well as other
biological properties. Moreover emphasis was given in rapid and effective
isolation of bioactive compounds from plant extracts with counter-current
chromatography (CCC) approaches.
Plant extracts of eleven endemic species of the Fabaceae (Leguminosae) family
were studied for their possible antioxidant, chemopreventive and antibacterial
properties. Methanolic and aqueous extracts of above-ground parts of plants
showed the highest activity in antioxidant / chemopreventive tests, while in
antimicrobial tests the non-polar extracts appeared to be the most active.
Five species with important antioxidant and chemopreventive activity (Vicia
faba, Lotus edulis, Lotus longisiliquosus, Tetragonolobus purpureus, Lathyrus
laxiflorus subsp. Laxiflorus) were phytochemically investigated. Moreove,
Oryza sativa (Graminea) a plant known for its antioxidant properties, was also
investigated . From the above plants more than 100 compounds were isolated and
identified, of which 12 are new natural products. The isolated metabolites
belong to five main categories: flavonoids, simple phenolic compounds, phenolic
acids, carboxylic acids and triterpenes conjugated with ferulic acid.
The results of this work clearly shows that plants of the Fabaceae family, in
addition to their nutritional value, have a plethora of secondary metabolites
with significant biological activities and could be important sources of
antioxidants.
CounderCurent Chromatography (CCC) played a crucial role in the isolation of
natural products. The analysis of extracts of Vicia faba, Lotus logisiliquosus
and Tetragonolobus purpureus took place by off line coupling of CCC technique
with sephadex column or preparative HPLC. In the case of Lotus edulis and
Lathyrus laxiflorus, was achieved the direct isolation of active compounds
(flavonoids, isoflavones and phenolic acids) from the complex extract using
dual mode or gradient mode CCC. Emphasis was also given on the analysis of
non-polar mixtures and in efficient isolation of substances with increased
pharmacological interest (c-oryzanolis) from rice bran oil (RBO).
It is clearly indicated that Counter-Current Chromatography (CCC) is a valuable
technique and was successfully employed for rapid and effective separation of
natural compounds from crude active extracts. It is worth noting that the
transition from analytical to manufacturing application (scale-up) accompanied
by a clear improvement in the quality of separation which is very encouraging
for potential use of the technique on an industrial scale.
The structure elucidation of isolated compounds was performed with various
spectroscopic methods, mainly NMR spectroscopy and spectrometry HRMS.
Particular emphasis was placed on analysis and understanding of MS and NMR
spectra, in drawing conclusions and specific characteristic constants, to
easier and faster identification of molecules that belong to chemical classes
addressed by this research effort. Finally, the high efficiency liquid
chromatography connected in series with photodiode detector and Mass
Spectrometer High Resolution (UHPLC-DAD-APCI (±)-HRMS), can be used as a
selection method for the analysis and purity control of complex mixtures while
providing valuable information on the structural characteristics.
Keywords:
Fabaceae familly, CounderCarrent Chromatography, Gradient mode, HRMS, γ-oryzanol
