Supervisors info:
Αληγιάννης Νεκτάριος, Αναπληρωτής Καθηγητής, Τμήμα Φαρμακευτικής, Ε.Κ.Π.Α.
Summary:
One of the main objectives of the Pharmacognosy and Natural Products Laboratory is the study of terrestrial plant organisms in terms of its chemical constituents and the discovery of new natural products with notable biological properties. The aim is to create new knowledge in the field of natural products and to investigate their possible potential as pharmaceuticals, cosmeceuticals and agroceuticals.
In this thesis, the secondary metabolite content of the fruits of Paliurus spina-christi (Rhamnaceae) was studied. There are not many references about this plant in the bibliography, not only regarding its phytochemical content, but also about any possible biological activity. Paliurus spina-christi, commonly known as Christ’s thorn, is a bush that has been used for centuries not only due to its economic importance, but also because of its use in the traditional medicine. Previous phytochemical studies that have been done on other species of the same genus, have resulted in the isolation and characterization of many interesting secondary metabolites. Thus, the aim of this thesis was the phytochemical study of the fruits of the aforementioned plant for the isolation of secondary metabolites which would justify the bibliographical biological properties and the use of the plant in the traditional medicine.
More specifically, mature fruits of the plant were collected, powdered and subjected to exhaustive extractions with a series of solvents of increasing polarity. On the basis of the evaluation of the TLC and 1H-NMR profile of the produced extracts, the methanolic and aqueous extracts were selected for further study. The processing of the methanolic extract, which was fractionated by a series of liquid – liquid extractions, resulted in the fraction of Ethyl Acetate (EtOAc) which was selected for further chromatographic separations. Eleven secondary metabolites were isolated from this fraction, which belong to the chemical classes of phenolics, sterols, triterpenes and cyclopeptide alkaloids. One of the three metabolites (metabolite 8) of the last class constitutes a new natural product. Subsequently, the aqueous extract was studied and the presence of natural products that belong to the class of flavonoids was identified. Another aqueous extract of the plant, which was prepared based on a traditional medicine recipe was passed through XAD-4 and XAD-7 resins and, after that, to a series of chromatographic purifications by using Solid Phase Extraction techniques. The produced fractions were studied by HPLC and 1H-NMR and the presence of flavonoids was confirmed. Among the future objectives of this work is the further evaluation of the use of this plant in the traditional medicine (further in vivo evaluation is currently in process) and its possible correlation with the isolated and elucidated metabolites.
Keywords:
Paliurus spina-christi, Rhamnaceae, Chemistry of Natural Products, phytosterols, triterpenes, cyclopeptide alkaloids
