Undescribed Amaryllidaceae Alkaloids from Zephyranthes citrina and Their Cytotoxicity.

This phytochemical study presents the isolation of eight alkaloids from Zephyranthes citrina Baker. The structures of the new alkaloids, zephycitrine (1) and 6-oxonarcissidine (2), were established by analysis of spectroscopic and spectrometric data. Processing the EtOH extract under acid-base conditions yielded the unreported isolation artifacts 3 and 4. This work also provides analytical data for alkaloids not properly described in the literature (5 and 6). The hippeastidine/zephyranine scaffolds in derivatives 3, 4, and 8-10 are also thoroughly discussed. Furthermore, a cytotoxicity screening of 25 Amaryllidaceae alkaloids isolated from Z. citrina was performed. Only the known alkaloids haemanthamine (12), haemanthidine (13), and lycorine (27) showed significant cell growth inhibition.

Development of a capillary electrophoresis method for the separation of flavonolignans in silymarin complex.

CE method for the baseline separation of structurally similar flavonolignans silybin A, silybin B, isosilybin A, isosilybin B, silychristin, silydianin, and their precursor taxifolin in silymarin complex has been developed and validated. The optimized background electrolyte was 100 mmol/L boric acid (pH 9.0) containing 5 mmol/L heptakis(2,3,6-tri-O-methyl)-ß-CD and 10% (v/v) of methanol. The separation was carried out in an 80.5/72 cm (50 µm id) fused silica capillary at +25 kV with UV detection at 200 nm. Genistein (10 µg/mL) was used as internal standard. The resolution between the diastereomers of silybin and isosilybin was 1.73 and 2.59, respectively. The method was validated for each analyte in a concentration range of 2.5-50 µg/mL. The calibration curves were rectilinear with correlation coefficients ≥0.9972. The method was applied to determine flavonolignans in two dietary supplements containing Silybum marianum extract. The accuracy was evaluated by comparing the results of the CE analyses of the dietary supplements with those of the reference United States Pharmacopeial HPLC method. The unpaired t-test did not show a statistically significant difference between the results of both the proposed CE and the reference method (p > 0.05, n = 3).

Derivatives of montanine-type alkaloids and their implication for the treatment of Alzheimer's disease: Synthesis, biological activity and in silico study.

Alzheimers disease (AD) is the most common neurodegenerative disorder, characterized by neuronal loss and cognitive impairment. Currently, very few drugs are available for AD treatment, and a search for new therapeutics is urgently needed. Thus, in the current study, twenty-eight new derivatives of montanine-type Amaryllidaceae alkaloids were synthesized and evaluated for their ability to inhibit human recombinant acetylcholinesterase (hAChE) and butyrylcholinesterase (hBuChE). Three derivatives (1n, 1o, and 1p) with different substitution patterns demonstrated significant selective inhibitory potency for hAChE (IC50 < 5 µM), and one analog, 1v, showed selective hBuChE inhibition activity (IC50 = 1.73 ± 0.05 µM). The prediction of CNS availability, as disclosed by the BBB score, suggests that the active compounds in this survey should be able pass through the blood-brain barrier (BBB). Cytotoxicity screening and docking studies were carried out for the two most pronounced cholinesterase inhibitors, 1n and 1v.

Alkaloids of Zephyranthes citrina (Amaryllidaceae) and their implication to Alzheimer's disease: Isolation, structural elucidation and biological activity.

Twenty known Amaryllidaceae alkaloids of various structural types, and one undescribed alkaloid of narcikachnine-type, named narcieliine (3), have been isolated from fresh bulbs of Zephyranthes citrina. The chemical structures of the isolated alkaloids were elucidated by a combination of MS, HRMS, 1D and 2D NMR, and CD spectroscopic techniques, and by comparison with literature data. The absolute configuration of narcieliine (3) has also been determined. Compounds isolated in a sufficient quantity were evaluated for their in vitro acetylcholinesterase (AChE; E.C. 3.1.1.7), butyrylcholinesterase (BuChE; E.C. 3.1.1.8), and prolyl oligopeptidase (POP; E.C. 3.4.21.26) inhibition activities. Significant human AChE/BuChE (hAChE/hBuChE) inhibitory activity was demonstrated by the newly described alkaloid narcieliine (3), with IC50 values of 18.7 ± 2.3 µM and 1.34 ± 0.31 µM, respectively. This compound is also predicted to cross the blood-brain barrier (BBB) through passive diffusion. The in vitro data were further supported by in silico studies of 3 in the active site of hAChE/hBuChE.

Functionalized aromatic esters of the Amaryllidaceae alkaloid haemanthamine and their in vitro and in silico biological activity connected to Alzheimer's disease.

A novel series of aromatic esters (1a-1m) related to the Amaryllidaceae alkaloid (AA) haemanthamine were designed, synthesized and tested in vitro with particular emphasis on the treatment of neurodegenerative diseases. Some of the synthesized compounds revealed promising acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory profile. Significant human AChE (hAChE) inhibition was demonstrated by 11-O-(3-nitrobenzoyl)haemanthamine (1j) with IC50value of 4.0 ± 0.3 µM. The strongest human BuChE (hBuChE) inhibition generated 1-O-(2-methoxybenzoyl)haemanthamine (1g) with IC50 value 3.3 ± 0.4 µM. Moreover, 11-O-(2-chlorbenzoyl)haemanthamine (1m) was able to inhibit both enzymes in dose-dependent manner. The mode of hAChE and hBuChE inhibition was minutely inspected using enzyme kinetic analysis in tandem with in silico experiments, the latter elucidating crucial interaction in 1j-, 1m-hAChE and 1g-, 1m-hBuChE complexes. The blood-brain barrier (BBB) permeability was investigated applying the parallel artificial membrane permeation assay (PAMPA) to predict the CNS availability of the compounds.

Carltonine-derived compounds for targeted butyrylcholinesterase inhibition.

The investigation into human butyrylcholinesterase (hBChE) inhibitors as therapeutic agents for Alzheimer's disease (AD) holds significant promise, addressing both symptomatic relief and disease progression. In the pursuit of novel drug candidates with a selective BChE inhibition pattern, we focused on naturally occurring template structures, specifically Amaryllidaceae alkaloids of the carltonine-type. Herein, we explored a series of compounds implementing an innovative chemical scaffold built on the 3- and 4-benzyloxy-benzylamino chemotype. Notably, compounds 28 (hBChE IC50 = 0.171 ± 0.063 µM) and 33 (hBChE IC50 = 0.167 ± 0.018 µM) emerged as top-ranked hBChE inhibitors. In silico simulations elucidated the binding modes of these compounds within hBChE. CNS availability was predicted using the BBB score algorithm, corroborated by in vitro permeability assessments with the most potent derivatives. Compound 33 was also inspected for aqueous solubility, microsomal and plasma stability. Chemoinformatics analysis validated these hBChE inhibitors for oral administration, indicating favorable gastrointestinal absorption in compliance with Lipinski's and Veber's rules. Safety assessments, crucial for the chronic administration typical in AD treatment, were conducted through cytotoxicity testing on human neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cell lines.

Highly selective butyrylcholinesterase inhibitors related to Amaryllidaceae alkaloids - Design, synthesis, and biological evaluation.

Butyrylcholinesterase (BChE) is one of the most frequently implicated enzymes in the advanced stage of Alzheimer's disease (AD). As part of our endeavors to develop new drug candidates for AD, we have focused on natural template structures, namely the Amaryllidaceae alkaloids carltonine A and B endowed with high BChE selectivity. Herein, we report the design, synthesis, and in vitro evaluation of 57 novel highly selective human BChE (hBChE) inhibitors. Most synthesized compounds showed hBChE inhibition potency ranging from micromolar to low nanomolar scale. Compounds that revealed BChE inhibition below 100 nM were selected for detailed biological investigation. The CNS-targeted profile of the presented compounds was confirmed theoretically by calculating the BBB score algorithm, these data were corroborated by determining the permeability in vitro using PAMPA-assay for the most active derivatives. The study highlighted compounds 87 (hBChE IC50 = 3.8 ± 0.2 nM) and 88 (hBChE IC50 = 5.7 ± 1.5 nM) as the top-ranked BChE inhibitors. Compounds revealed negligible cytotoxicity for the human neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cell lines compared to BChE inhibitory potential. A crystallographic study was performed to inspect the binding mode of compound 87, revealing essential interactions between 87 and hBChE active site. In addition, multidimensional QSAR analyses were applied to determine the relationship between chemical structures and biological activity in a dataset of designed agents. Compound 87 is a promising lead compound with potential implications for treating the late stages of AD.

Monoterpene indole alkaloids from Vinca minor L. (Apocynaceae): Identification of new structural scaffold for treatment of Alzheimer's disease.

One undescribed indole alkaloid together with twenty-two known compounds have been isolated from aerial parts of Vinca minor L. (Apocynaceae). The chemical structures of the isolated alkaloids were determined by a combination of MS, HRMS, 1D, and 2D NMR techniques, and by comparison with literature data. The NMR data of several alkaloids have been revised, corrected, and missing data have been supplemented. Alkaloids isolated in sufficient quantity were screened for their in vitro acetylcholinesterase (AChE; E.C. 3.1.1.7) and butyrylcholinesterase (BuChE; E.C. 3.1.1.8) inhibitory activity. Selected compounds were also evaluated for prolyl oligopeptidase (POP; E.C. 3.4.21.26), and glycogen synthase 3ß-kinase (GSK-3ß; E.C. 2.7.11.26) inhibition potential. Significant hBuChE inhibition activity has been shown by (-)-2-ethyl-3[2-(3-ethylpiperidinyl)-ethyl]-1H-indole with an IC50 value of 0.65 ± 0.16 µM. This compound was further studied by enzyme kinetics, along with in silico techniques, to reveal the mode of inhibition. This compound is also predicted to cross the blood-brain barrier (BBB) through passive diffusion.

Amaryllidaceae Alkaloids of Different Structural Types from Narcissus L. cv. Professor Einstein and Their Cytotoxic Activity.

In this detailed phytochemical study of Narcissus cv. Professor Einstein, we isolated 23 previously known Amaryllidaceae alkaloids (1-23) of several structural types and one previously undescribed alkaloid, 7-oxonorpluviine. The chemical structures were identified by various spectroscopic methods (GC-MS, LC-MS, 1D, and 2D NMR spectroscopy) and were compared with literature data. Alkaloids which had not previously been isolated and studied for cytotoxicity before and which were obtained in sufficient amounts were assayed for their cytotoxic activity on a panel of human cancer cell lines of different histotype. Above that, MRC-5 human fibroblasts were used as a control noncancerous cell line to determine the general toxicity of the tested compounds. The cytotoxicity of the tested alkaloids was evaluated using the WST-1 metabolic activity assay. The growth of all studied cancer cell lines was inhibited by pancracine (montanine-type alkaloid), with IC50 values which were in the range of 2.20 to 5.15 µM.

Recent trends in determination of thiamine and its derivatives in clinical practice.

Over the last five decades, many methods to analyze thiamine (vitamin B1) and its phosphorylated forms in urine, whole blood, serum, plasma and erythrocytes have been proposed. Some of the methods are presently used in routine practice, but analytical problems regarding reproducibility, standardization, lack of automation, time consuming procedures for pretreatment and analysis are often discussed. With modern approaches to bioanalysis in clinical research of vitamins, whole processes can be automated, making analysis less time consuming, with reduced consumption of solvents and samples. This review critically discusses various analytical techniques, their advantages and disadvantages that are used for determination of thiamine and its derivatives in clinical practice, with emphasis on accurate, reliable and fast analytical procedures.

Systematic Optimization of Liquid-Liquid Extraction for Isolation of Unidentified Components.

We present a systematic approach for predicting the best solvents for selective extraction of components with unknown structure from complex mixtures (e.g., natural products)-a tool promising dramatic simplification of extraction process optimization. Its key advantage is that identification of the component(s) is unnecessary-prediction is based on a small set of experimental distribution coefficients (obtained using a combination of shake-flask extraction and chromatographic analysis) rather than structure-based descriptors. The methodology is suitable for the very common situations in practice where the desired compound needs to be separated from unknown impurities (i.e., selectively extracted from the mixture), as well as for large-scale and high-throughput work. The proof-of-concept methodology was developed and evaluated using an extensive set of experimental distribution data of lignin-related compounds obtained in this work.