Ioannis P. Gerothanassis

Learn More
The goal of this study was to monitor the anti-proliferative activity of Rosmarinus officinalis and Salvia officinalis extracts against cancer cells and to correlate this activity with their phytochemical profiles using liquid chromatography/diode array detection/electrospray ion trap tandem mass spectrometry (LC/DAD/ESI-MS(n)). For the quantitative(More)
Structure elucidation of natural products usually relies on a combination of NMR spectroscopy with mass spectrometry whereby NMR trails MS in terms of the minimum sample amount required. In the present study, the usefulness of on-line solid-phase extraction (SPE) in LC-NMR for peak storage after the LC separation prior to NMR analysis is demonstrated. The(More)
Oregano vulgare L. ssp. hirtum (Greek oregano), Salvia fruticosa (Greek sage), and Satureja hortensis (summer savory) were examined as potential sources of phenolic antioxidant compounds. The antioxidant capacities (antiradical activity by DPPH* test, phosphatidylcholine liposome oxidation, Rancimat test) and total phenol content were determined in the(More)
A novel strategy for NMR analysis of mixtures of oleanolic and ursolic acids that occur in natural products is described. These important phytochemicals have similar structure and their discrimination and quantification is rather difficult. We report herein the combined use of proton-carbon heteronuclear single-quantum coherence ((1)H-(13)C HSQC) and(More)
The newly established hyphenated instrumentation of LC/DAD/SPE/NMR and LC/UV/(ESI)MS techniques have been applied for separation and structure verification of the major known constituents present in Greek Hypericum perforatum extracts. The chromatographic separation was performed on a C18 column. Acetonitrile-water was used as a mobile phase. For the(More)
In this report the rational design, synthesis and pharmacological properties of an amide-linked cyclic antagonist analogue of the guinea pig myelin basic protein epitope MBP(72-85) are described. Design of the potent cyclic analogue was based on 2D NOESY nuclear magnetic resonance and molecular dynamics studies carried out in the linear antagonist(More)
The cis/trans conformational equilibrium of the two Ac-Pro isomers of the beta-turn model dipeptide [13C]-Ac-L-Pro-D-Ala-NHMe, 98% 13C enriched at the acetyl carbonyl atom, was investigated by the use of variable temperature gradient enhanced 1H-nmr, two-dimensional (2D) 1H,1H nuclear Overhauser effect spectroscopy (NOESY), 13C,1H one-dimensional(More)
Olive oil compounds is a dynamic research area because Mediterranean diet has been shown to protect against cardiovascular disease and cancer. Olive leaves, an easily available natural material of low cost, share possibly a similar wealth of health benefiting bioactive phytochemicals. In this work, we investigated the antioxidant potency and(More)
Conformational analysis of angiotensin I (AI) and II (AII) peptides has been performed through 2D 1H-NMR spectroscopy in dimethylsulfoxide and 2,2,2-trifluoroethanol/H2O. The solution structural models of AI and AII have been determined in dimethylsulfoxide using NOE distance and 3JHNHalpha coupling constants. Finally, the AI family of models resulting from(More)
An overview of recent advances in nuclear magnetic resonance (NMR) coupled with separation technologies and their application in natural product analysis is given and discussed. The different modes of LC-NMR operation are described, as well as how technical improvements assist in establishing LC-NMR as an important tool in the analysis of plant-derived(More)