Marcela Šafratová

In Vitro Inhibitory Effects of 8-O-Demethylmaritidine and Undulatine on Acetylcholinesterase and Their Predicted Penetration across the Blood-Brain Barrier.

Alzheimers disease is the most common cause of dementia. Currently, acetylcholinesterase (AChE) inhibition is the most widely used therapeutic treatment. A large number of naturally occurring compounds have been found to inhibit AChE. In this report the mechanism of AChE inhibition of two Amaryllidaceae alkaloids, 8-O-demethylmaritidine (1) and undulatine (2), and their possible penetration across the blood-brain barrier have been studied. Both compounds act via a mixed inhibition mechanism. Based on the parallel artificial permeation assay (PAMPA) for the prediction of blood-brain barrier (BBB) penetration, only 2 should be able to cross the BBB by passive permeation.

Isoquinoline alkaloids as prolyl oligopeptidase inhibitors.

Prolyl oligopeptidase is a cytosolic serine peptidase that hydrolyses proline-containing peptides at the carboxy terminus of proline residues. It has been associated with schizophrenia, bipolar affective disorder, and related neuropsychiatric disorders and therefore may have important clinical implications. Thirty-one isoquinoline alkaloids of various structural types, previously isolated in our laboratory, were screened for their ability to inhibit prolyl oligopeptidase. Promising results have been showed by alkaloids californidine (IC50=55.6±3.5 μM), dihydrosanquinarine (IC50=99.1±7.6 μM), corypalmine (IC50=128.0±10.5 μM) and N-methyllaurotetanine (IC50=135.0±11.7 μM).

Isoquinoline Alkaloids from Fumaria officinalis L. and Their Biological Activities Related to Alzheimer's Disease

Two new isoquinoline alkaloids, named fumaranine (2) and fumarostrejdine (10), along with 18 known alkaloids were isolated from aerial parts of Fumaria officinalis. The structures of the isolated compounds were elucidated on the basis of spectroscopic analyses and by comparison with literature data. The absolute configuration of the new compound 2 was determined by comparing its circular dichroism spectra with those of known analogs. Compounds isolated in sufficient amounts were evaluated for their acetylcholinesterase, butyrylcholinesterase, prolyl oligopeptidase (POP), and glycogen synthase kinase‐3β inhibitory activities. Parfumidine (8) and sinactine (15) exhibited potent POP inhibition activities (IC50 99±5 and 53±2 μM, resp.).

Isolation of Amaryllidaceae alkaloids from Nerine bowdenii W. Watson and their biological activities

Twenty-two isoquinoline alkaloids (1–22) were isolated from fresh bulbs of Nerine bowdenii (Amaryllidaceae) by standard chromatographic methods. The chemical structures were elucidated by MS, and 1D and 2D NMR spectroscopic analyses, and by comparison with literature data. 6-O-Demethylbelladine (11) and 4′-O-demethylbelladine (12) are reported here for the first time. Compounds isolated in sufficient amounts were evaluated for their acetylcholinesterase, and butyrylcholinesterase inhibition activity using Ellmans method. In the prolyl oligopeptidase assay, Z-Gly-Pro-p-nitroanilide was used as substrate. Untested alkaloids were also screened for their cytotoxic activity against p53-mutated Caco-2 and HT-29 colorectal adenocarcinoma cells. At the same time, healthy small intestine cells FH-74 Int were used to determine overall toxicity against noncancerous cells. The crinine-type alkaloid buphanisine (7) demonstrated interesting cytotoxicity against both tested cancer cell lines with IC50 values of 8.59 ± 0.15 μM for Caco-2 and 5.32 ± 1.70 μM for HT-29.

Comparative cytotoxicity of chelidonine and homochelidonine, the dimethoxy analogues isolated from Chelidonium majus L. (Papaveraceae), against human leukemic and lung carcinoma cells.

BACKGROUND The search for new anticancer compounds is a crucial element of natural products research. PURPOSE In this study the effects of naturally occurring homochelidonine in comparison to chelidonine on cell cycle progression and cell death in leukemic T-cells with different p53 status are described. METHODS The mechanism of cytotoxic, antiproliferative, apoptosis-inducing effects and the effect on expressions of cell cycle regulatory proteins was investigated using XTT assay, Trypan blue exclusion assay, flow cytometry, Western blot analysis, xCELLigence, epi-fluorescence and 3D super resolution microscopy. A549 cells were used for xCELLigence, clonogenic assay and for monitoring microtubule stability. RESULTS We found that homochelidonine and chelidonine displayed significant cytotoxicity in examined blood cancer cells with the exception of HEL 92.1.7 and U-937 exposed to homochelidonine. Unexpectedly, homochelidonine and chelidonine-induced cytotoxicity was more pronounced in Jurkat cells contrary to MOLT-4 cells. Homochelidonine showed an antiproliferative effect on A549 cells but it was less effective compared to chelidonine. Biphasic dose-depended G1 and G2/M cell cycle arrest along with the population of sub-G1 was found after treatment with homochelidonine in MOLT-4 cells. In variance thereto, an increase in G2/M cells was detected after treatment with homochelidonine in Jurkat cells. Treatment with chelidonine induced cell cycle arrest in the G2/M cell cycle in both MOLT-4 and Jurkat cells. MOLT-4 and Jurkat cells treated with homochelidonine and chelidonine showed features of apoptosis such as phosphatidylserine exposure, a loss of mitochondrial membrane potential and an increase in the caspases -3/7, -8 and -9. Western blots indicate that homochelidonine and chelidonine exposure activates Chk1 and Chk2. Studies conducted with fluorescence microscopy demonstrated that chelidonine and homochelidonine inhibit tubulin polymerization in A549 cells. CONCLUSION Collectively, the data indicate that chelidonine and homochelidonine are potent inducers of cell death in cancer cell lines, highlighting their potential relevance in leukemic cells.

Amaryllidaceae Alkaloids as Potential Glycogen Synthase Kinase-3β Inhibitors

Glycogen synthase kinase-3β (GSK-3β) is a multifunctional serine/threonine protein kinase that was originally identified as an enzyme involved in the control of glycogen metabolism. It plays a key role in diverse physiological processes including metabolism, the cell cycle, and gene expression by regulating a wide variety of well-known substances like glycogen synthase, tau-protein, and β-catenin. Recent studies have identified GSK-3β as a potential therapeutic target in Alzheimer´s disease, bipolar disorder, stroke, more than 15 types of cancer, and diabetes. GSK-3β is one of the most attractive targets for medicinal chemists in the discovery, design, and synthesis of new selective potent inhibitors. In the current study, twenty-eight Amaryllidaceae alkaloids of various structural types were studied for their potency to inhibit GSK-3β. Promising results have been demonstrated by alkaloids of the homolycorine-{9-O-demethylhomolycorine (IC50 = 30.00 ± 0.71 µM), masonine (IC50 = 27.81 ± 0.01 μM)}, and lycorine-types {caranine (IC50 = 30.75 ± 0.04 μM)}.