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

Identification of haemanthamine as a phytotoxic alkaloid in Narcissus pseudonarcissus L. (Daffodil) emerging buds

Emerging buds of Narcissus pseudonarcissus were found to accumulate the alkaloid haemanthamine (1) at high concentrations, exceeding that of narciclasine (2), the most abundant constituent in bulbs of the plant. A phytoactivity screening assay demonstrated the novel phytotoxicity of haemanthamine against Raphanus sativus (radish), Lactuca sativus (lettuce), Triticum aestivum (red wheat), Solanum lycopersicum (tomato), Cucumis sativus (cucumber), Ipomoea (Morning glory), and Lens culinaris (lentil). Haemanthamine (1) phytotoxicity was found to exceed that of the commercial herbicide glyphosate and less toxic than narciclasine (2).

Antiproliferative activity and apoptosis-inducing mechanism of Amaryllidaceae alkaloid montanine on A549 and MOLT-4 human cancer cells

The isoquinoline alkaloids found in Amaryllidaceae are attracting attention due to attributes that can be harnessed for the development of new drugs. The possible molecular mechanisms by which montanine exerts its inhibitory effects against cancer cells have not been documented. In the present study, montanine, manthine and a series of 15 semisynthetic montanine analogues originating from the parent alkaloid montanine were screened at a single test dose of 10 μM to explore their cytotoxic activities against a panel of eight cancer cell lines and one non-cancer cell line. Among montanine and its analogues, montanine and its derivatives 12 and 14 showed the highest cytostatic activity in the initial single-dose screening. However, the native montanine exhibited the greatest antiproliferative activity against cancer cells, with a lower mean IC50 value of 1.39 µM, compared to the displayed mean IC50 values of 2.08 µM for 12 and 3.57 µM for 14. Montanine exhibited the most potent antiproliferative activity with IC50 values of 1.04 µM and 1.09 µM against Jurkat and A549 cell lines, respectively. We also evaluated montanine's cytotoxicity and cell death mechanisms. Our results revealed that montanine triggered apoptosis of MOLT-4 cells via caspase activation, mitochondrial depolarisation and Annexin V/PI double staining. The Western blot results of MOLT-4 cells showed that the protein levels of phosphorylated Chk1 Ser345 were upregulated with increased montanine concentrations. Our findings provide new insights into the mechanisms underlying the cytostatic, cytotoxic and pro-apoptotic activities of montanine alkaloids in lung adenocarcinoma A549 and leukemic MOLT-4 cancer cell types.

A developmental gradient reveals biosynthetic pathways to eukaryotic toxins in monocot geophytes

Numerous eukaryotic toxins that accumulate in geophytic plants are valuable in the clinic, yet their biosynthetic pathways have remained elusive. A lead example is the >150 Amaryllidaceae alkaloids (AmAs) including galantamine, an FDA-approved treatment for Alzheimer's disease. We show that while AmAs accumulate to high levels in many tissues in daffodils, biosynthesis is localized to nascent, growing tissue at the base of leaves. A similar trend is found for the production of steroidal alkaloids (e.g. cyclopamine) in corn lily. This model of active biosynthesis enabled elucidation of a complete set of biosynthetic genes for the production of AmAs. Taken together, our work sheds light on the developmental and enzymatic logic of diverse alkaloid biosynthesis in daffodil. More broadly, it suggests a paradigm for biosynthesis regulation in monocot geophytes where plants are protected from herbivory through active charging of newly formed cells with eukaryotic toxins that persist as aboveground tissue develops.

Derivatives of Amaryllidaceae Alkaloid Ambelline as Selective Inhibitors of Hepatic Stage of Plasmodium berghei Infection In Vitro

The incidence rate of malaria and the ensuing mortality prompts the development of novel antimalarial drugs. In this work, the activity of twenty-eight Amaryllidaceae alkaloids (1-28) belonging to seven different structural types was assessed, as well as twenty semisynthetic derivatives of the β-crinane alkaloid ambelline (28a-28t) and eleven derivatives of the α-crinane alkaloid haemanthamine (29a-29k) against the hepatic stage of Plasmodium infection. Six of these derivatives (28h, 28m, 28n and 28r-28t) were newly synthesized and structurally identified. The most active compounds, 11-O-(3,5-dimethoxybenzoyl)ambelline (28m) and 11-O-(3,4,5-trimethoxybenzoyl)ambelline (28n), displayed IC₅₀ values in the nanomolar range of 48 and 47 nM, respectively. Strikingly, the derivatives of haemanthamine (29) with analogous substituents did not display any significant activity, even though their structures are quite similar. Interestingly, all active derivatives were strictly selective against the hepatic stage of infection, as they did not demonstrate any activity against the blood stage of Plasmodium infection. As the hepatic stage is a bottleneck of the plasmodial infection, liver-selective compounds can be considered crucial for further development of the malaria prophylactics.

Amaryllidaceae Alkaloids from Clivia miniata (Lindl.) Bosse (Amaryllidaceae): Isolation, Structural Elucidation, and Biological Activity

Clivia miniata (Amaryllidaceae) is an herbaceous evergreen flowering plant that is endemic to South Africa and Swaziland and belongs to one of the top-10 traded medicinal plants in informal medicine markets in South Africa. The species has been reported as the most important component of a traditional healer's pallet of healing plants. Eighteen known Amaryllidaceae alkaloids (AAs) of various structural types, and one undescribed alkaloid of homolycorine-type, named clivimine B (3), were isolated from Clivia miniata. The chemical structures of the isolated alkaloids were elucidated by a combination of MS, HRMS, 1D and 2D NMR techniques and by comparison with literature data. Compounds isolated in a sufficient quantity, and not tested previously, were evaluated for their in vitro acetylcholinesterase (AChE; E.C. 3.1.1.7) and butyrylcholinesterase (BuChE; E.C. 3.1.1.8) inhibition activities.

A Review on Herbal Secondary Metabolites Against COVID-19 Focusing on the Genetic Variants of SARS-CoV-2

Context: An outbreak of the new coronavirus disease 2019 (COVID-19) was reported in Wuhan, China, in December 2019, subsequently affecting countries worldwide and causing a pandemic. Although several vaccines, such as mRNA vaccines, inactivated vaccines, and adenovirus vaccines, have been licensed in several countries, the danger of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants persists. To date, Alpha (B.1.1.7), Beta (B.1.351, B.1.351.2, B.1.351.3), Delta (B.1.617.2, AY.1, AY.2, AY. 3), Gamma (P.1, P.1.1, P.1.2), and Iota (B.1 .526) circulating in the United States, Kappa (B.1.617.1) in India, Lambda (C.37) in Peru and Mu (B.1.621) in Colombia are considered the variants of concern and interest. Evidence Acquisition: Data were collected through the end of August 2021 by searching PubMed, Scopus, and Google Scholar databases. There were findings from in silico, in vitro cell-based, and non-cell-based investigations. Results: The potential and safety profile of herbal medicines need clarification to scientifically support future recommendations regarding the benefits and risks of their use. Conclusions: Current research results on natural products against SARS-CoV-2 and variants are discussed, and their specific molecular targets and possible mechanisms of action are summarized.

Monitoring the Green Vegetation Period of Two Narcissus Taxa by Non-Destructive Analysis of Selected Physiological and Morphological Properties

In a pot experiment, an early-flowering Narcissus pseudonarcissus cv. ‘Dutch Master’ (DM) and late-flowering N. poeticus cultural form (PO) were examined. The photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), photosynthetic water use efficiency (WUE), relative chlorophyll content (CCI) and chlorophyll fluorescence (F) were measured regularly. Leaf length, scape length and weight of the plant organs were also measured. The DM cultivar had higher gs and lower E values than the PO on most measuring dates (season average: gs: DM: 165.34, PO: 123.63; E: DM: 1.39, PO: 1.78 mmol H2O m−2s−1). The A curve was similar for the two taxa, except for the first measuring dates. The basic F values (F0, Fm, Fv) for DM were lower and CCI values were higher than for PO (season average of CCI: DM: 94.82, PO: 60.34). The Fm/F0, Fv/F0 and CCI curves were well described by a second order equation. The seasonal change of F and CCI values was the greatest for both taxa near the leaf tip. Bulb growth occurred in the two taxa in approximately the same calendar period, regardless of flowering time. A significant part of the leaf growth in DM occurred after flowering, while the leaves of PO reached their mature size by flowering.

Cytotoxic Agents in the Minor Alkaloid Groups of the Amaryllidaceae

Over 600 alkaloids have to date been identified in the plant family Amaryllidaceae. These have been arranged into as many as 15 different groups based on their characteristic structural features. The vast majority of studies on the biological properties of Amaryllidaceae alkaloids have probed their anticancer potential. While most efforts have focused on the major alkaloid groups, the volume and diversity afforded by the minor alkaloid groups have promoted their usefulness as targets for cancer cell line screening purposes. This survey is an in-depth review of such activities described for around 90 representatives from 10 minor alkaloid groups of the Amaryllidaceae. These have been evaluated against over 60 cell lines categorized into 18 different types of cancer. The montanine and cripowellin groups were identified as the most potent, with some in the latter demonstrating low nanomolar level antiproliferative activities. Despite their challenging molecular architectures, the minor alkaloid groups have allowed for facile adjustments to be made to their structures, thereby altering the size, geometry, and electronics of the targets available for structure-activity relationship studies. Nevertheless, it was seen with a regular frequency that the parent alkaloids were better cytotoxic agents than the corresponding semisynthetic derivatives. There has also been significant interest in how the minor alkaloid groups manifest their effects in cancer cells. Among the various targets and pathways in which they were seen to mediate, their ability to induce apoptosis in cancer cells is most appealing.

Pancracine, a Montanine-Type Amaryllidaceae Alkaloid, Inhibits Proliferation of A549 Lung Adenocarcinoma Cells and Induces Apoptotic Cell Death in MOLT-4 Leukemic Cells

Pancracine, a montanine-type Amaryllidaceae alkaloid (AA), is one of the most potent compounds among natural isoquinolines. In previous studies, pancracine exhibited cytotoxic activity against diverse human cancer cell lines in vitro. However, further insight into the molecular mechanisms that underlie the cytotoxic effect of pancracine have not been reported and remain unknown. To fill this void, the cell proliferation and viability of cancer cells was explored using the Trypan Blue assay or by using the xCELLigence system. The impact on the cell cycle was determined by flow cytometry. Apoptosis was evaluated by Annexin V/PI and by quantifying the activity of caspases (-3/7, -8, and -9). Proteins triggering growth arrest or apoptosis were detected by Western blotting. Pancracine has strong antiproliferative activity on A549 cells, lasting up to 96 h, and antiproliferative and cytotoxic effects on MOLT-4 cells. The apoptosis-inducing activity of pancracine in MOLT-4 cells was evidenced by the significantly higher activity of caspases. This was transmitted through the upregulation of p53 phosphorylated on Ser392, p38 MAPK phosphorylated on Thr180/Tyr182, and upregulation of p27. The pancracine treatment negatively altered the proliferation of A549 cells as a consequence of an increase in G1-phase accumulation, associated with the downregulation of Rb phosphorylated on Ser807/811 and with the concomitant upregulation of p27 and downregulation of Akt phosphorylated on Thr308. This was the first study to glean a deeper mechanistic understanding of pancracine activity in vitro. Perturbation of the cell cycle and induction of apoptotic cell death were considered key mechanisms of pancracine action.

Biosynthesis and Biological Activities of Newly Discovered Amaryllidaceae Alkaloids

Alkaloids are an important group of specialized nitrogen metabolites with a wide range of biochemical and pharmacological effects. Since the first publication on lycorine in 1877, more than 650 alkaloids have been extracted from Amaryllidaceae bulbous plants and clustered together as the Amaryllidaceae alkaloids (AAs) family. AAs are specifically remarkable for their diverse pharmaceutical properties, as exemplified by the success of galantamine used to treat the symptoms of Alzheimer's disease. This review addresses the isolation, biological, and structure activity of AAs discovered from January 2015 to August 2020, supporting their therapeutic interest.

Unveiling pharmacological studies provide new insights on Mangifera longipes and Quercus gomeziana

Mangifera longipes and Quercus gomeziana both is an ethnomedicinally important Asian herb that has been known for numerous healing activity of tribal people. The present research aims to investigate the phytochemical analysis with in vitro, in vivo possibilities of the soluble ethanol extract of M. longipes root (EEMLR) and Q. gomeziana leaves (EEQGL) by an experimental approach. The plant extract of EEMLR and EEQGL was found secondary metabolites, notably steroids, glycosides, tannins, flavonoids, saponins, gums, and alkaloids. Additionally, the extract showed significant activity in antioxidant, antipyretic, anti-inflammatory, membrane stabilization, cytotoxic, thrombolytic, and analgesic activities while no response in antibacterial activity. Our findings reveal that soluble ethanol extract of EEMLR and EEQGL is safe, which can be an effective source for exploring new medicinal products. This research's outcomes may provide potentials for mitigating pyrexia, inflammation, pain, cellular toxicity, and coagulation.

Amaryllidaceae Alkaloids of Belladine-Type from Narcissus pseudonarcissus cv. Carlton as New Selective Inhibitors of Butyrylcholinesterase

Thirteen known (1-12 and 16) and three previously undescribed Amaryllidaceae alkaloids of belladine structural type, named carltonine A-C (13-15), were isolated from bulbs of Narcissus pseudonarcissus cv. Carlton (Amaryllidaceae) by standard chromatographic methods. Compounds isolated in sufficient amounts, and not tested previously, 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 BuChE (hBUChE) inhibitory activity was demonstrated by newly described alkaloids carltonine A (13) and carltonine B (14) with IC₅₀ values of 913 ± 20 nM and 31 ± 1 nM, respectively. Both compounds displayed a selective inhibition pattern for hBuChE with an outstanding selectivity profile over AChE inhibition, higher than 100. The in vitro data were further supported by in silico studies of the active alkaloids 13 and 14 in the active site of hBuChE.

Chemical and Biological Aspects of Montanine-Type Alkaloids Isolated from Plants of the Amaryllidaceae Family

Plants of the Amaryllidaceae family are promising therapeutic tools for human diseases and have been used as alternative medicines. The specific secondary metabolites of this plant family, called Amaryllidaceae alkaloids (AA), have attracted considerable attention due to their interesting pharmacological activities. One of them, galantamine, is already used in the therapy of Alzheimer’s disease as a long acting, selective, reversible inhibitor of acetylcholinesterase. One group of AA is the montanine-type, such as montanine, pancracine and others, which share a 5,11-methanomorphanthridine core. So far, only 14 montanine-type alkaloids have been isolated. Compared with other structural-types of AA, montanine-type alkaloids are predominantly present in plants in low concentrations, but some of them display promising biological properties, especially in vitro cytotoxic activity against different cancerous cell lines. The present review aims to summarize comprehensively the research that has been published on the Amaryllidaceae alkaloids of montanine-type.