Cytotoxic Cyclotides: Structure, Activity, and Mode of Action

Electrospray ion technology (ESI) mass spectrometry (MS) in conjunction with fluid chromatography (LC) is an efficient tool for that identification of drug metabolites. Utilizing this hyphenated strategy in conjunction with proper example pretreatment, the metabolic pathways of this analgesic drug ketobemidone were investigated in human pee and rat microdialysate from blood and brain. Two novel phase I metabolites (ketobemidone N-oxide and meta-hydroxymethoxyketobemidone) and three novel phase II metabolites (glucuronic acid conjugates of ketobemidone, norketobemidone and hydroxymethoxyketobemidone) were acknowledged in human urine. Further, norketobemidone and ketobemidone N-oxide were discovered in rat microdialysate from brain after regional distribution of ketobemidone in striatum. This suggests how the brain itself has the probability to process ketobemidone.Synthetic ketobemidone metabolites were used to compare of retention times and tandem MS spectra using the possible metabolites recovered from the biological samples. The conjugated metabolites were identified by accurate mass measurements and tandem MS spectra of the aglycones. The precision of the estimated masses was superior to 2.1 ppm for just two out of three conjugates in presence of internal standard.On-line micro-SPE was efficiently utilized for trapping and desalting of the microdialysates. The tiny SPE pre-column achieved it possible to inject approximately 100 times more sample on the analytical column as compared to injection without pre-column.

Contents: Cytotoxic Cyclotides: Structure, Activity, and Mode of Action

1. CyclotidesThe cyclic cystine knot
From gene to cyclotide sequence
Historical perspectives
Biological activities
Aims of the present study
2. Cyclotide isolation and structure
Plant material
Extraction and fractionation
Isolation and purification
Sequence determination
3-D modelled structures
3. Cyclotide cytotoxicity
Cancer cell line assay
Cyclotide isolation guided by cytotoxic activity
Structure–activity studies
Kinetics and morphology
Membrane effects and liposomes
Hollow fibre assay in vitro
Toxicity in vivo
Hollow fibre assay in vivo
4. Discussion
Isolation and structure characterization
Structure–activity properties
Mode of action
Cytotoxicity and selectivity
Anti-tumour activity
Cyclotides and plant biology
5. Concluding remarks
6. Populärvetenskaplig sammanfattning…