Galanthamine, Plicamine, and Secoplicamine Alkaloids from Zephyranthes candida and Their Anti-acetylcholinesterase and Anti-inflammatory Activities

Anti-inflammatory Principles of the Plant Family Amaryllidaceae

There is considerable interest in the utilisation of plants against inflammation. Over 50 species of the plant family Amaryllidaceae are known for such usage in traditional medicine. This review was undertaken to identify the chemical principles responsible for these anti-inflammatory effects. It describes the findings from in vitro, in vivo and in silico studies, as well as the probes made on the mechanisms of action. The literature search returned over 600 hits, of which around 130 were chosen for their relevance to the text. Over 140 compounds have thus far been screened for anti-inflammatory effects. These were mostly isoquinoline alkaloids but also included other classes of secondary metabolites such as chromones, flavonoids and triterpenoids. In vitro studies were carried out in mononuclear cells such as lymphocytes, monocytes, neutrophils and macrophages, against which no serious side effects were observed. The constituents were also effective against inflammation induced by physical and chemical stimuli in a variety of murine test subjects. Chief among the compounds were the isoquinoline alkaloids lycorine and narciclasine, which displayed potent effects against pain, swelling, asthma and arthritis, amongst others. From a mechanistic perspective, several of the compounds were shown to mediate in inflammatory pathways, notably via the modulation of both pro-inflammatory (such as NF-κB, TNF-α and IL-1) and anti-inflammatory (such as IL-10 and TGF-β) factors. Useful insights also emerged from active-site docking studies of some of the compounds. The Amaryllidaceae affords a rich and diverse platform for the discovery of potential anti-inflammatory drugs.

A Convenient Synthesis of Novel Isoxazolidine and Isoxazole Isoquinolinones Fused Hybrids

Isoxazolidine, isoxazole, and isoquinolinone rings are present in the structure of several natural products and/or pharmaceutically interesting compounds. In this work, facile and efficient pathways have been developed for the preparation of fused frameworks bearing those heterocycles. The successful approaches for both isoxazolidine/isoquinolinone and isoxazole/isoquinolinone hybrid syntheses relied initially on 1,3-dipolar cycloadditions of nitrones and nitrile oxides to indenone and 2-propargylbenzamide, respectively. The construction of the isoquinolinone lactam system followed by performing a selective Schmidt reaction for isoxazolidine derivatives (two steps overall), whereas the isoxazole lactams were reached via an Ullmann-type cyclisation (three steps overall). Key observations were made regarding the stereo- and regioselectivities of the reactions employed, and small libraries of the targeted hybrids were prepared, demonstrating the general applicability of these strategies.

Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities

Twenty-six structurally diverse Amaryllidaceae alkaloids, including ten undescribed compounds named zephyranines A-I and 6-O-ethylnerinine, two undescribed natural products zephyranthine-6-one and 3-O-deacetyl-sternbergine, were isolated from whole plants of Zephyranthes candida. Their structures were determined by HRESIMS, 1D and 2D NMR, CD data analysis, NMR and ECD calculations, and single-crystal X-ray diffraction analysis. All structures were classified into nine framework types: 10b,11-seco-crinine, graciline, crinine, homolycorine, trisphaeridine, lycorine, galasine, tazettine, and belladine. Zephyranine A represents the first naturally occurring 10b,11-seco-crinine type alkaloid, and zephyranine B is the sixth graciline type alkaloid. 6-O-ethylnerinine is an artifact from the extraction and isolation. All isolates were evaluated for their acetylcholinesterase (AChE) inhibitory and anti-inflammatory activities. Zephyranines A, G, and H exhibited moderate AChE inhibitory activities, with IC₅₀ values of 8.2, 39.0, and 10.8 μM, respectively. Zephyranine B, haemanthamine, haemanthidine, 11-hydroxyvittatine, and 8-demethoxy-10-O-methylhostasine exhibited potent anti-inflammatory activity on the LPS-induced NO production in RAW264.7 mouse macrophages with IC₅₀ values of 21.3, 4.6, 12.2, 5.6, and 17.4 μM, respectively. Structure-activity-relationship analysis and docking studies indicated that interactions with the key Trp286 and Tyr337 residues are required for potent AChE inhibitors.

Targets and mechanisms of Alpinia oxyphylla Miquel fruits in treating neurodegenerative dementia

The dried and ripe fruits of Alpinia oxyphylla and ripe fruits of Alpinia oxyphylla Miquel (AO) have the effects of tonifying kidney-essence and nourishing intelligence and thus have been widely used in treating dementia. Alzheimer's disease (AD) is a typical form of neurodegenerative dementia with kidney-essence deficiency in Traditional Chinese Medicine (TCM). So far, there is a lack of systematic studies on the biological basis of tonifying kidney-essence and nourishing intelligence and the corresponding phytochemicals. In this study, we investigated the targets of AO in tonifying kidney-essence and nourishing intelligence based on the key pathophysiological processes of neurodegenerative dementia. According to ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry data and Lipinski's rule of five, 49 bioactive phytochemicals from AO were identified, and 26 of them were found to target 168 key molecules in the treatment of neurodegenerative dementia. Nine phytochemicals of AO were shown to target acetylcholinesterase (ACHE), and 19 phytochemicals were shown to target butyrylcholinesterase (BCHE). A database of neurodegenerative dementia with kidney-essence deficiency involving 731 genes was constructed. Furthermore, yakuchinone B, 5-hydroxy-1,7-bis (4-hydroxy-3-methoxyphenyl) heptan-3-one (5-HYD), oxyhylladiketone, oxyphyllacinol, butyl-β-D-fructopyranoside, dibutyl phthalate, chrysin, yakuchinone A, rhamnetin, and rhamnocitrin were identified as the key phytochemicals from AO that regulate the pathogenesis of neurodegenerative dementia in a multitargeted manner. The approach of studying the pharmacological mechanism underlying the effects of medicinal plants and the biological basis of TCM syndrome may be helpful in studying the translation of TCM.

Antiproliferative Amaryllidaceae alkaloids from the bulbs of Hymenocallis littoralis (Jacq.) Salisb

Seven undescribed Amaryllidaceae alkaloids classified into four types, including the plicamine-type, secoplicamine-type, belladine-type and pretazettine-type, along with another three alkaloids that have not been isolated from plant material and seven known alkaloids, were isolated from the bulbs of Hymenocallis littoralis (Jacq.) Salisb. The structures were elucidated on the basis of various spectroscopic methods (UV, IR, MS, NMR, ECD). The isolated alkaloids were screened for antiproliferative activity against four human tumour cell lines (HepG2, HeLa, SPC-A-1, FaDu) through MTT assay, and some alkaloids exhibited potent cytotoxicity. Meanwhile, cell morphological assessment, flow cytometric analysis, Western blot analysis, clone formation and scratch wound assays were utilized for an undescribed belladine-type alkaloid and two known alkaloids, which had antiproliferative effects on the HepG2 cell line via induction of apoptosis in a dose-dependent manner. A pair of diastereoisomers of Amaryllidaceae alkaloids exhibited significant differences in antiproliferative activity. In addition, the alkaloids also possessed the potential to inhibit tumour cell migration.

Promising Therapeutic Candidate for Myocardial Ischemia/Reperfusion Injury: What Are the Possible Mechanisms and Roles of Phytochemicals?

Percutaneous coronary intervention (PCI) is one of the most effective reperfusion strategies for acute myocardial infarction (AMI) despite myocardial ischemia/reperfusion (I/R) injury, causing one of the causes of most cardiomyocyte injuries and deaths. The pathological processes of myocardial I/R injury include apoptosis, autophagy, and irreversible cell death caused by calcium overload, oxidative stress, and inflammation. Eventually, myocardial I/R injury causes a spike of further cardiomyocyte injury that contributes to final infarct size (IS) and bound with hospitalization of heart failure as well as all-cause mortality within the following 12 months. Therefore, the addition of adjuvant intervention to improve myocardial salvage and cardiac function calls for further investigation. Phytochemicals are non-nutritive bioactive secondary compounds abundantly found in Chinese herbal medicine. Great effort has been put into phytochemicals because they are often in line with the expectations to improve myocardial I/R injury without compromising the clinical efficacy or to even produce synergy. We summarized the previous efforts, briefly outlined the mechanism of myocardial I/R injury, and focused on exploring the cardioprotective effects and potential mechanisms of all phytochemical types that have been investigated under myocardial I/R injury. Phytochemicals deserve to be utilized as promising therapeutic candidates for further development and research on combating myocardial I/R injury. Nevertheless, more studies are needed to provide a better understanding of the mechanism of myocardial I/R injury treatment using phytochemicals and possible side effects associated with this approach.

Micromorphology and anatomy of the flower of Zephyranthes candida (Amaryllidaceae)

The use of morphological features of flowers in the taxonomy of plants is becoming increasingly important. The structure of the Zephyranthes candida (Lindl.) Herb. flowers on permanent cross-sectional and longitudinal sections was studied using a light microscope. The genus Zephyranthes belongs to the subtribe Hippeastrinae Walp. tribe Hippeastreae Sweet., family Amaryllidaceae s.l. Microscopic studies of the flower are considered as a tool to identify hitherto unknown structural adaptations of plants to specialized pollination methods and to elucidate the first stages of fruit morphogenesis, as many features of the fruit appear at the flower stage. The morphometric parameters, morphology, anatomy, and vascular anatomy of the ovary were described by using the flower’s transverse sections. Ten flowers of Z. candida were sectioned using standard methods of Paraplast embedding and serial sectioning at 20 μm thickness. Sections were stained with Safranin and Astra Blau and mounted in Eukitt. It was found that in the studied species the tepals have multi-bundle traces of 10–12 leading bundles. We consider the gynoecium of the studied species to be eusincarpous. The vascular system of the inferior ovary consists of three dorsal and three septal bundles, paired ventral bundles of carpels, which form ovule traces. For the first time, the presence of the following gynoecium zones was detected: a synascidiate structural zone with a height of about 360 μm and a fertile symplicate structural zone with a height of about 1560 μm and a hemisymplicate zone of 480 μm. Septal nectaries appear in the hemisymplicate zone and open with nectary split at the base of the style, the total height of the septal nectary is 760 μm. The ovary roof is 280 μm. Bifurcated dorsal and septal bundles of carpels have been identified, which can be considered as adaptations of the early stages of fruit morphogenesis to opening. Anatomical features of the ovary of Z. candida are numerous vascular bundles in the pericarpium, non-lignified endocarp at the flower stage, we consider as adaptations to the formation of juicy fruit. New data on the anatomical structure of the flower are a significant addition to the information on antecological and post-anthetic features of the studied species. Also, these data can be used in the construction of parsimony branches of the family Amaryllidaceae.

Iridium-Catalyzed Asymmetric Cascade Allylation/Pictet-Spengler Cyclization Reaction for the Enantioselective Synthesis of 1,3,4-Trisubstituted Tetrahydroisoquinolines

An iridium-catalyzed trifluoroacetic acid-promoted asymmetric cascade allylation/Pictet-Spengler cyclization reaction of azomethine ylides with aromatic allylic alcohols is reported. This protocol provides a facile and scalable method for the construction of 1,3,4-trisubstituted tetrahydroisoquinolines containing two stereogenic centers in good yields (up to 96%) with generally excellent diastereo- and enantioselectivities (up to >20:1 dr and >99% ee). Furthermore, a series of aromatic heterocycle-fused piperidines were also obtained with excellent enantiocontrol by this methodology.

Chaetocochin J, an epipolythiodioxopiperazine alkaloid, induces apoptosis and autophagy in colorectal cancer via AMPK and PI3K/AKT/mTOR pathways

Colorectal cancer (CRC) is the third commonly diagnosed malignancy and the second leading cause of cancer death worldwide. Development of novel chemotherapeutics is crucial. Natural products are the main source of drug discovery, and epipolythiodioxopiperazine (ETP) alkaloids are one kind of them have been reported to have potent biological activities. In the present study, we first isolated Chaetocochin J (CJ), an ETP alkaloid from the secondary metabolites of Chaetomium sp, and studied the anti-CRC activity and mechanism of it. The results showed that CJ exhibits potent proliferation inhibition effect, its IC₅₀ to CRC cells are around 0.5 µM. CJ also induces apoptosis of CRC cells in a dose-dependent manner, and this effect is stronger than topotecan. In addition, CJ treatment triggers autophagic flux in CRC cells, inhibition of autophagy by chloroquine didn't affect CJ-induced apoptosis and growth inhibition, suggesting CJ may simultaneously induced apoptosis and autophagy in CRC cells. We further explored the mechanism of action, and found that CJ exerts its anti-CRC function via AMPK and PI3K/AKT/mTOR pathways and further regulation of their downstream signaling cascade in CRC cells, including apoptosis and autophagy. These data potently suggest that CJ may be a potential drug candidate for CRC treatment.

Laccase-Catalyzed 1,4-Dioxane-Mediated Synthesis of Belladine N-Oxides with Anti-Influenza A Virus Activity

Belladine N-oxides active against influenza A virus have been synthetized by a novel laccase-catalyzed 1,4-dioxane-mediated oxidation of aromatic and side-chain modified belladine derivatives. Electron paramagnetic resonance (EPR) analysis confirmed the role of 1,4-dioxane as a co-oxidant. The reaction was chemo-selective, showing a high functional-group compatibility. The novel belladine N-oxides were active against influenza A virus, involving the early stage of the virus replication life cycle.

Mass propagation through direct and indirect organogenesis in three species of genus Zephyranthes and ploidy assessment of regenerants through flow cytometry

Genus Zephyranthes consists of economically important plant species due to their high ornamental value and presence of valuable bioactive compounds. However, this genus propagates by asexual division only which gives slow propagation rate. Plant tissue culture has the potential to provide efficient techniques for rapid multiplication and genetic improvement of the genus. In this work, a dual in vitro regeneration system through callus mediated shoot regeneration and direct shoot regeneration in species Zephyranthes candida, Zephyranthes grandiflora and Zephyranthes citrina was investigated. Bulb, leaf and root explants were cultured on Murashige and Skoog (MS) medium amended with different plant growth regulators (PGR's) viz. 2,4-dichlorophenoxyacetic acid (2,4-D), 1-Naphthalene acetic acid (NAA), 6-benzyl amino purine (BAP), N-phenyl-N'-1,2,3 -thiadiazol-5-ylurea (TDZ), 6-Furfuryl- aminopurine (KIN) alone or in combinations for callus induction and regeneration. Only bulb explants showed callus induction and regeneration response on different PGR combinations with a varied response in callus induction percentage, callus color and callus texture. Creamish compact callus (CC) was induced on 2 mg L[Formula: see text] 2,4-D, brown friable callus (BF) on 2 mg L[Formula: see text] NAA + 1 mg L[Formula: see text] BAP and green friable callus (GF) callus on 1 mg L[Formula: see text] KIN + 3 mg L[Formula: see text] NAA. The maximum shoot multiplication from different callus types (indirect organogenesis) was achieved on 2 mg L[Formula: see text] BAP alone without combinations. Bulb explants of Z. grandiflora induced maximum callus induction percentage (86.4%) and shoot regeneration percentage (83.5%) with the maximum 08 shoots per 150 mg callus mass. The induction and regeneration response was followed in the order of Z. grandiflora > Z. candida > Z. citrina. Similarly, maximum direct organogenesis from bulb explants was obtained in Z. grandiflora (93.3%) followed by Z. candida (91.5%) and Z. citrina (90.4%) on 3 mg L[Formula: see text] TDZ amended MS media. Adventitious root induction was achieved on 2 mg L[Formula: see text] IBA with a maximum of 8 roots per shoot. The in vitro raised plantlets were successfully acclimatized in the field with 85% survival efficiency. The genome size (2C DNA content) of the field-grown plants and in vitro regenerated plants, evaluated through flow cytometry technique, were similar and showed no ploidy changes. An efficient mass propagation protocol was established for obtaining plants with unaltered genome size in the three species of Zephyranthes.

Discovery of natural anti-inflammatory alkaloids: Potential leads for the drug discovery for the treatment of inflammation

Inflammation is an adaptive response of the immune system to tissue malfunction or homeostatic imbalance. Corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) are frequently applied to treat varieties of inflammatory diseases but are associated with gastrointestinal, cardiovascular, and kidney side effects. Developing more effective and less toxic agents remain a challenge for pharmaceutical chemist due to the complexity of the different inflammatory processes. Alkaloids are widely distributed in plants with diverse anti-inflammatory activities, providing various potential lead compounds or candidates for the design and discovery of new anti-inflammatory drug candidates. Therefore, re-examining the anti-inflammatory alkaloid natural products is advisable, bringing more opportunities. In this review, we summarized and described the recent advances of natural alkaloids with anti-inflammatory activities and possible mechanisms in the period from 2009 to 2020. It is hoped that this review of anti-inflammatory alkaloids can provide new ideas for researchers engaged in the related fields and potential lead compounds for the discovery of anti-inflammatory drugs.

Application of HPLC-DAD for In Vitro Investigation of Acetylcholinesterase Inhibition Activity of Selected Isoquinoline Alkaloids from Sanguinaria canadensis Extracts

Isoquinoline alkaloids may have a wide range of pharmacological activities. Some of them have acetylcholinesterase activity inhibition. Nowadays, neurodegenerative disorders such as Alzheimer’s disease have become a serious public health problem. Searching for new effective compounds with inhibited acetylcholinesterase activity is one of the most significant challenges of modern scientific research. The aim of this study was the in vitro investigation of acetylcholinesterase activity inhibition of extracts obtained from Sanguinaria canadensis collected before, during and after flowering. The acetylcholinesterase activity inhibition of these extracts has not been previously tested. The aim was also to quantify selected alkaloids in the investigated extracts by high performance liquid chromatography (HPLC). The analyses of alkaloid content were performed using HPLC in reversed phase (RP) mode using Polar RP column and mobile phase containing acetonitrile, water and ionic liquid (IL). The acetylcholinesterase activity inhibition of the tested plant extracts and respective alkaloid standards were examined using high performance liquid chromatography with diode-array detector (HPLC-DAD) for the quantification of 5-thio-2-nitro-benzoic acid, which is the product of the reaction between the thiocholine (product of the hydrolysis of acetylthiocholine reaction) with Ellman reagent. The application of the HPLC method allowed for elimination of absorption of interfering components, for example, alkaloids such as sanguinarine and berberine. It is revealed that the HPLC method can be successfully used for the evaluation of the acetylcholinesterase inhibitory activity in samples such as plant extracts, especially those containing colored components adsorbing at wavelength in the range 405–412 nm. The acetylcholinesterase inhibition activity synergy of pairs of alkaloid standards and mixture of all investigated alkaloids was also determined. Most investigated alkaloids and all Sanguinaria canadensis extracts exhibited very high acetylcholinesterase activity inhibition. IC₅₀ values obtained for alkaloid standards were from 0.36 for berberine to 23.13 µg/mL for protopine and from 61.24 to 89.14 µg/mL for Sanguinaria canadensis extracts. Our investigations demonstrated that these plant extracts can be recommended for further in vivo experiments to confirm their acetylcholinesterase activity inhibition.

Streamlined targeting of Amaryllidaceae alkaloids from the bulbs of Crinum scillifolium using spectrometric and taxonomically-informed scoring metabolite annotations

Four undescribed alkaloids have been isolated from the bulbs of the previously unstudied Crinum scillifolium. These compounds were targeted following a state-of-the-art molecular networking strategy comprising a dereplication against in silico databases and re-ranking of the candidate structures based on taxonomically informed scoring. The unreported structures span across a variety of Amaryllidaceae alkaloids appendages. Their structures were unambiguously elucidated by thorough interpretation of their HRESIMS and 1D and 2D NMR data, and comparison to literature data. DFT-NMR calculations were performed to support the determined relative configurations of scillitazettine and scilli-N-desmethylpretazettine and their absolute configurations were mitigated by comparison between experimental and theoretically calculated ECD spectra. The lack of a methyl group on the nitrogen atom in the structure of scilli-N-desmethylpretazettine series is highly unusual in the pretazettine/tazettine series but the most original structural feature in it lies in its 11α disposed hydrogen, which is new to pretazettines. The antiplasmodial as well as the cytotoxic activities against the human colon cancer cell line HCT116 were evaluated, revealing mild to null activities.

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.

Monoterpene indole alkaloids with diverse skeletons from the stems of Rauvolfia vomitoria and their acetylcholinesterase inhibitory activities

Nine undescribed monoterpene indole alkaloids, rauvomitorine A-I, including an unprecedented C-9-methoxymethylene-sarpagine framework alkaloid, two rare suaveoline framework type alkaloids, and six yohimbine framework type alkaloids, as well as eleven known alkaloids, were isolated from the stems of Rauvolfia vomitoria Afzel. (Apocynaceae). The structures of the unreported alkaloids were elucidated by extensive spectroscopic analysis and single-crystal X-ray diffraction analysis with Cu Kα radiation. Rauvomitorine A with an unreported framework type represents the first example of C-9-methoxymethylene-sarpagine alkaloids and its plausible biosynthetic pathway was proposed. All the isolated alkaloids were evaluated their acetylcholinesterase inhibitory (AChE) activities and cytotoxicity against five cancer cell lines and some of them exhibited potential anti-AChE activities with IC₅₀ values ranging from 49.76 to 186.62 μM. Importantly, this is the first report of the AChE inhibitory activities on suaveoline framework type alkaloids, suggesting this type of alkaloids may be valuable sources for the discovery of AChE inhibitory agents. A preliminary structure-activity relationship for AChE inhibitory activities of the isolated alkaloids is also discussed, providing some clues to designing lead compounds for AChE inhibitors.

Monoterpene indole alkaloids with acetylcholinesterase inhibitory activity from the leaves of Rauvolfia vomitoria

Seventeen monoterpene indole alkaloids, including seven new alkaloids (1-7) and ten known analogues (8-17), were isolated and identified from the leaves of R. vomitoria. The structures of new alkaloids were elucidated by extensive spectroscopic analysis and single-crystal X-ray diffraction analysis. Rauvomitorine I (1) represents the first example of an unprecedented C₂₂ yohimbine-type monoterpene indole alkaloid featuring a carboxymethyl at C-14. The exceedingly rare vobasenal (2-3) and affinisine oxindole (5-6) framework type alkaloids are first reported from the Rauvolfia genus. Most notably, the structure of vobasenal-type alkaloids (2-3) were first determined by single-crystal X-ray diffraction analyses. Alkaloids 1-17 were tested their cytotoxicity against five cancer cell lines, however, none of them showed significant cytotoxicity at a concentration of 40 μM. All the isolated alkaloids were evaluated their acetylcholinesterase (AChE) inhibitory activities. Alkaloid 3 exhibited significant anti-AChE activity with an IC₅₀ value of 16.39 ± 1.41 μM and alkaloids 8 and 10 showed moderate anti-AChE activities whereas the others (2, 9, 13, and 17) were weak inhibitors. This is the first report of vobasenal-type alkaloids as AChE inhibitors, indicating this type of alkaloids may be important sources for the discovery of new AChE inhibitors. A preliminary structure-activity relationship for AChE inhibitory activities showed the presence of the N-methyl group in vobasenal-type alkaloids may be essential for anti-AChE activity. Further molecular docking studies of vobasenal-type alkaloids revealed that interaction with Trp133 and Trp86 residues at hydrophobic subsite are necessary for the AChE inhibitory activities. This study not only enriches the chemical diversity of alkaloids in Apocynaceae plants but also provides new potential leading compounds and versatile scaffolds for the design and development of new AChE inhibitors to treat AD.

Bioguided Isolation and Structure Identification of Acetylcholinesterase Enzyme Inhibitors from Drynariae Rhizome

Drynariae Rhizome, widely distributed in southern China, was clinically used as a traditional treatment for cognitive disfunction, such as Alzheimer's disease (AD). The aim of our work was to evaluate the AChE inhibition activities of extracts of Drynariae Rhizome and pure compounds using a bioguided fractionation procedure. The classical approach for screening potential AChE inhibitors was developed by Ellman. However, the background color of compounds or herb extracts remained uncertain and frequently interfered with the detection of the secondary reaction, thereby easily yielding false positive or false negative results. Here, a high-throughput assay monitoring the transformation of iodized choline from iodized acetylcholine catalyzed by AChE was established based on UPLC-MS/MS. The bioguided fractionation of the extract using this method resulted in the isolation of eight AChE inhibitory flavonoids, including naringenin, eriodictyol, kaempferol, luteolin, astragalin, luteolin-7-O-β-D-glucoside, naringin, and neoeriocitrin, with the IC₅₀ values of 3.81 ± 0.21 μM, 7.19 ± 0.62 μM, 11.09 ± 1.02 μM, 17.26 ± 0.23 μM, 18.24 ± 2.33 μM, 17.13 ± 1.02 μM, 26.4 ± 1.17 μM, and 22.49 ± 1.25 μM. It is assumed that the identified flavonoids contribute to the AChE inhibition activity of Drynariae Rhizome. These results are in agreement with the traditional uses of Drynariae Rhizome for AD.

Chemodiversity, chemotaxonomy and chemoecology of Amaryllidaceae alkaloids

The Amaryllidaceae alkaloids are a distinctive chemotaxonomic feature of the subfamily Amaryllidoideae of the family Amaryllidaceae, which consists of 59 genera and >800 species distributed primarily in tropical and subtropical areas. Since the first isolation, ca. 140 ago, >600 structurally diverse Amaryllidaceae alkaloids have been reported from ca. 350 species (44% of all species in the subfamily). A few have been found in other plant families, but the majority are unique to the Amaryllidoideae. These alkaloids have attracted considerable research interest due to their wide range of biological and pharmacological activities, which have been extensively reviewed. In this chapter we provide a review of the 636 structures of isolated or tentatively identified alkaloids from plants of the Amaryllidoideae and their classification into 42 skeleton types, as well as a discussion on their distribution, and chemotaxonomical and chemoecological aspects.

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.

Sesquiterpenoids from the aerial parts of Conyza japonica and their inhibitory activity against nitric oxide production

Four new sesquiterpenoids, conyterpenols A - D (1-4), along with nineteen known analogues (5-23) were isolated from the aerial parts of Conyza japonica. The structures of 1-4 were determined through spectroscopic analysis, while their absolute configurations were determined by comparison of calculated and experimental electronic circular dichroism (ECD) spectra. Conyterpenol D (4) was a new type of sesquiterpenoid with a seven-membered lactone ring. Compounds 1-23 were evaluated for their inhibitory activity against LPS-induced nitric oxide production in RAW264.7 macrophages and cytotoxicity against human hepatoma cell line (HepG2) and human breast adenocarcinoma cell line (MCF-7). Compounds 3, 4, and 12 displayed moderate inhibition against NO production with IC₅₀ values in the range of 26.4-33.6 μM. And all compounds showed no obvious cytotoxicity against these two cancer cell lines at 100 μM.

Galanthamine improves myocardial ischemia-reperfusion-induced cardiac dysfunction, endoplasmic reticulum stress-related apoptosis, and myocardial fibrosis by suppressing AMPK/Nrf2 pathway in rats

Background

Myocardial ischemia/reperfusion (I/R) injury is an important cause of myocardial infarction and heart failure after cardiovascular surgery. Galanthamine (Gal) is an important Amaryllidaceae alkaloid with anti-acetylcholinesterase and anti-inflammatory activity. The purpose of this study was to investigate the role of Gal in myocardial I/R injury.

Methods

In this study, an animal model of myocardial I/R injury was constructed, and the rats were divided into five groups (n=10): the sham, I/R model, I/R + Gal (1 mg/kg), I/R + Gal (3 mg/kg), and I/R + Aspirin (20 mg/kg) groups. The expression of related proteins was detected by Western blotting and Immunohistochemistry, and Histological lesion was detected by HE staining.

Results

Results showed that Gal improves I/R-induced cardiac dysfunction in rats. Moreover, Gal inhibits I/R-induced endoplasmic reticulum stress (ERS)-related apoptosis by suppressing the expression of CHOP, Cleaved caspase 12, and caspase 3, and promoting the expression of CADD34 and BiP in rats. Furthermore, Gal mitigates I/R-induced myocardial fibrosis through restraining the expression of α-SMA and Collagen I in rats. Mechanically, Gal promoted the expression of AMPKα1, Nrf2 and HO-1. However, AMPK inhibitor Compound C exhibited the opposite effects. Collectively, this finding suggests that Gal improves I/R-induced cardiac dysfunction, ERS-related apoptosis, and myocardial fibrosis by activating AMPK/Nrf2 pathway in myocardial I/R rats.

Conclusions

Given this evidence, Gal may be a potential therapeutic drug for the treatment of I/R injury.

ZYH005, a novel DNA intercalator, overcomes all-trans retinoic acid resistance in acute promyelocytic leukemia

Despite All-trans retinoic acid (ATRA) has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological cancer, there remains a clinical challenge that many high-risk APL patients who fail to achieve a complete molecular remission or relapse and become resistant to ATRA. Herein, we report that 5-(4-methoxyphenethyl)-[1, 3] dioxolo [4, 5-j] phenanthridin-6(5H)-one (ZYH005) exhibits specific anticancer effects on APL and ATRA-resistant APL in vitro and vivo, while shows negligible cytotoxic effect on non-cancerous cell lines and peripheral blood mononuclear cells from healthy donors. Using single-molecule magnetic tweezers and molecule docking, we demonstrate that ZYH005 is a DNA intercalator. Further mechanistic studies show that ZYH005 triggers DNA damage, and caspase-dependent degradation of the PML-RARa fusion protein. As a result, APL and ATRA-resistant APL cells underwent apoptosis upon ZYH005 treatment and this apoptosis-inducing effect is even stronger than that of arsenic trioxide and anticancer agents including 5-fluorouracil, cisplatin and doxorubicin. Moreover, ZYH005 represses leukemia development in vivo and prolongs the survival of both APL and ATRA-resistant APL mice. To our knowledge, ZYH005 is the first synthetic phenanthridinone derivative, which functions as a DNA intercalator and can serve as a potential candidate drug for APL, particularly for ATRA-resistant APL.

Borges W, Lacerda V. Cytotoxic and Genotoxic Activities of Alkaloids from the Bulbs of Griffinia gardneriana and Habranthus itaobinus (Amaryllidaceae)

Background:

Amaryllidaceae plants are known to be a great source of alkaloids, which are considered an extensive group of compounds encompassing a wide range of biological activities. The remarkable cytotoxic activities observed in most of the Amaryllidaceae alkaloids derivatives have prompt the chemical and biological investigations in unexplored species from Brazil.

Objective:

To evaluate the cytotoxic and genotoxic properties of alkaloids of Griffinia gardneriana and Habranthus itaobinus bulbs and study the role of caspase-3 as a molecular apoptosis mediator.

Methods:

Methanolic crude extracts of Griffinia gardneriana and Habranthus itaobinus bulbs were submitted to acid-base extraction to obtain alkaloid-enriched fractions. The obtained fractions were fractionated using chromatographic techniques leading to isolation and identification of some alkaloids accomplished via HPLC and 1H-NMR, respectively. Molecular docking studies assessed the amount of free binding energy between the isolated alkaloids with the caspase-3 protein and also calculated the theoretical value of Ki. Studies have also been developed to evaluate in vitro cytotoxicity and genotoxicity in such alkaloids and apoptosis activation via the caspase pathway using both tumor and normal cell lines.

Results:

Seven alkaloids were isolated and identified. Among these, 11-hydroxyvittatine and 2-α-7- dimethoxyhomolycorine were not cytotoxic, whereas tazettine, trisphaeridine, and sanguinine only showed activity against the fibroblast lineage. Lycorine and pretazettine were 10 to 30 folds more cytotoxic than the other alkaloids, including cancerous lines, and were genotoxic and capable of promoting apoptosis via the caspase-3 pathway. This result supports data obtained in docking studies wherein these two compounds exhibited the highest free energy values.

Conclusion:

The cytotoxicity assay revealed that, among the seven alkaloids isolated, only lycorine and pretazettine were active against different cell lines, exhibiting concentration- and time-dependent cytotoxic actions alongside genotoxic action and the ability to induce apoptosis by caspase-3, a result consistent with those obtained in docking studies.

Sesquiterpenoids with diverse carbon skeletons from the roots of Cichorium glandulosum and their anti-inflammatory activities

A total of thirteen sesquiterpenoids with diverse skeletons including four new sesquiterpenoids, glandulosines A - D (1-4), a new natural product, glandulosine E (5), and eight known sesquiterpene lactones (6-13) were isolated from the roots of Cichorium glandulosum Boiss. et Huet (Asteraceae). Their structures were determined by extensive spectroscopic experiments including NMR, electronic circular dichroism (ECD), calculated ECD, Rh₂(OCOCF₃)₄-induced ECD, and single-crystal X-ray diffraction analysis, as well as chemical methods. This is the first report of the crystal structure of 11β,13-dihydrolactucin (11). Thirteen isolated sesquiterpenoids (1-13) were evaluated for their anti-inflammatory activities in vitro, and three guaiane sesquiterpene lactones, glandulosine E (5), scorzoside (9), and lactucin (10) showed moderate inhibitory activity against LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages.

Profiling of acetylcholinesterase inhibitory alkaloids from some Crinum, Habranthus and Zephyranthes species by GC-MS combined with multivariate analyses and in silico studies

Acetylcholinesterase (AChE) inhibitors remain the class of drugs used for the treatment of Alzheimer disease (AD). For the aim of discovering new sources of potent AChE inhibitors, a combined AChE-inhibitory activity together with alkaloid profiles by GC-MS, combined with multivariate statistical analysis for biomarkers determination and in silico studies were attempted. Strategy was applied on leaves, roots and bulbs of six aquatic and terrestrial Amaryllidaceae species. Thirty alkaloids were identified and the AChE inhibitory activities of the extracts were tested by in-vitro Ellman method. Principal bioactive markers were discovered by correlating AChE inhibitory activity with chemical fingerprints via PLS and OPLS modeling which revealed that galanthamine, lycoramine, caranine, tazettine and N-demethylgalanthamine were the most bio-significant markers. Furthermore, the molecular docking was performed to illustrate binding orientations of the top scoring alkaloids in the active site of human acetylcholinesterase. Suggested strategy revealed that, beside galanthamine, caranine, N-demethylgalanthamine, and lycoramine are promising AChE inhibitors.

Derivatives of the β-Crinane Amaryllidaceae Alkaloid Haemanthamine as Multi-Target Directed Ligands for Alzheimer's Disease

Twelve derivatives 1a–1m of the β-crinane-type alkaloid haemanthamine were developed. All the semisynthetic derivatives were studied for their inhibitory potential against both acetylcholinesterase and butyrylcholinesterase. In addition, glycogen synthase kinase 3β (GSK-3β) inhibition potency was evaluated in the active derivatives. In order to reveal the availability of the drugs to the CNS, we elucidated the potential of selected derivatives to penetrate through the blood-brain barrier (BBB). Two compounds, namely 11-O-(2-methylbenzoyl)-haemanthamine (1j) and 11-O-(4-nitrobenzoyl)-haemanthamine (1m), revealed the most intriguing profile, both being acetylcholinesterase (hAChE) inhibitors on a micromolar scale, with GSK-3β inhibition properties, and predicted permeation through the BBB. In vitro data were further corroborated by detailed inspection of the compounds’ plausible binding modes in the active sites of hAChE and hBuChE, which led us to provide the structural determinants responsible for the activity towards these enzymes.

Amaryllidaceae andSceletiumalkaloids

Recent progress on the isolation, identification, biological activity and synthetic studies of Amaryllidaceae alkaloids, as well as the structurally close alkaloids from theSceletiumgenus, published from July 2015 to June 2017 are reviewed.

Grayanane Diterpenoid Glucosides from the Leaves of Rhododendron micranthum and Their Bioactivities Evaluation

Thirteen new grayanane diterpenoid glucosides, 3- epi-grayanoside B (1), micranthanosides A-E (2-6), 7α-hydroxygrayanoside C (7), micranthanoside F (8), 14β-acetyoxymicranthanoside F (9), micranthanoside G (10), 14- O-acetylmicranthanoside G (11), 14β-hydroxypieroside A (12), and micranthanoside H (13), and six known analogues (14-19) were isolated from the leaves of Rhododendron micranthum. The structures of 1-19 were elucidated based on spectroscopic analysis, comparison with literature, and chemical methods. The absolute configurations of 3- epi-grayanoside B (1) and micranthanosides A (2) and C (4) were defined by single-crystal X-ray diffraction analysis. This is the first report of the crystal structures of grayanane diterpenoid glucosides. 3- epi-Grayanoside B (1) represents the first example of a 3α-oxygrayanane diterpenoid glucoside, and micranthanosides A-D (2-5) are the first examples of 5α-hydroxy-1-β H-grayanane diterpenoids. In addition, micranthanosides C-F (4-6 and 8) and 14β-acetyoxymicranthanoside F (9) represent the first examples of grayanane glucosides with the glucosylation at C-16. All the grayanane diterpenoid glucosides 1-19 were assayed for their anti-inflammatory, antitumor, and PTP1B inhibitory activities, but did not show significant activities at 40 μM. Grayanane diterpenoid glucosides 1-18 were evaluated for their antinociceptive activity, and compounds 2, 3, 7-10, 12, 13, and 16 showed significant antinociceptive effects with percentage inhibitions in excess of 50%.

Cytotoxic and anti-inflammatory active plicamine alkaloids from Zephyranthes grandiflora

Phytochemical investigation on the 95% EtOH extract of the whole plants of Zephyranthes grandiflora resulted in the isolation of six new 4a-epi-plicamine-type alkaloids, zephygranditines A-F (1-6), including three novel 11,12-seco-plicamine-type alkaloids. The structures of the isolated compounds were established based on 1D and 2D (¹H¹H COSY, HMQC, and HMBC) NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated alkaloids were tested in vitro for cytotoxic potential against seven malignant melanoma cell lines and inhibitory activity for nitric oxide (NO) production and Cox-1/Cox-2. As a result, alkaloids 1-3 exhibited some cytotoxic activity against all the tested tumor cell lines with IC₅₀ values <20 μM and 1 and 2 displayed anti-inflammatory activity in both assay of inhibitory activity for nitric oxide production and Cox-1/Cox-2.

Terrusnolides A-D, new butenolides with anti-inflammatory activities from an endophytic Aspergillus from Tripterygium wilfordii

Terrusnolides A-D (1-4), four butenolides were isolated from an endophytic Aspergillus from Tripterygium wilfordii. The structures of 1-4 were established by comprehensive spectroscopic analyses and electronic circular dichroism (ECD) calculation. It is interesting that 1 was a butenolide derived by a triple decarboxylation, while 2-4 were the metabolites with 4-benzyl-3-phenyl-5H-furan-2-one motif possessing an isopentene group fused to the benzene ring. In vitro anti-inflammatory effects of these isolates were evaluated in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. 1-4 exhibited excellent inhibitory effects on the production of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and nitric oxide (NO) in LPS-induced macrophages, comparable with the positive control (indomethacin). Those results indicated that, terrusnolides A-D might serve as new potential natural remedies for the treatment of inflammation.

Anti-inflammatory Grayanane Diterpenoids from the Leaves of Rhododendron molle

Thirteen new grayanane diterpenoids (1-13), a new dimeric grayanane diterpenoid, bimollfoliagein A (14), and 15 known analogues (15-29) were isolated from the leaves of Rhododendron molle. The structures of the new compounds (1-14) were determined by extensive spectroscopic data interpretation. The absolute configurations of 1-3, 7, 8, 16, 18, and 24 were defined by single-crystal X-ray diffraction analysis. Mollfoliagein A (1) represents the first example of a 2,3:11,16-diepoxy grayanane diterpenoid, featuring a cis/trans/cis/cis/trans-fused 3/5/7/6/5/5 hexacyclic ring system with a 7,13-dioxahexacyclo[10.3.3.0^1,11.0^4,9.0^6,8.0^14,17]octadecane scaffold. Diterpenoids 1-29 were evaluated for their anti-inflammatory activities in vitro, and 15, 16, 18, 19, 23-26, 28, and 29 exhibited significant inhibitory activities against nitric oxide production in lipopolysaccharide-induced RAW264.7 mouse macrophages with IC₅₀ values ranging from 2.8 to 35.4 μM. A preliminary structure-activity relationship for the anti-inflammatory activity of diterpenoids 1-29 is discussed.

Acetylcholinesterase Inhibitory Alkaloids from the Whole Plants of Zephyranthes carinata

Eleven new alkaloids (1-11), classified as the 12-acetylplicamine (1), N-deformyl-seco-plicamine (2), plicamine (3-6), 4a-epi-plicamine (7), seco-plicamine (8), and lycorine (9-11) framework types, along with 15 known alkaloids (12-26) were isolated from the whole plants of Zephyranthes carinata. The structures of the new alkaloids 1-11 were established by extensive spectroscopic data interpretation. The absolute configurations of 9 and 10 were defined by single-crystal X-ray diffraction analysis. Zephycarinatines A (1), B (2), and G (7) represent the first examples of 12-acetylplicamine, N-deformyl-seco-plicamine, and 4a-epi-plicamine alkaloids, respectively. Alkaloids 6, 11, 17, and 20-23 exhibited AChE inhibitory activities with IC₅₀ values ranging from 1.21 to 184.05 μM, and a preliminary structure-activity relationship is discussed.

Zephycandidine A, the First Naturally Occurring Imidazo[1,2-f]phenanthridine Alkaloid from Zephyranthes candida, Exhibits Significant Anti-tumor and Anti-acetylcholinesterase Activities

Zephycandidine A (1), the first naturally occurring imidazo[1,2-f]phenanthridine alkaloid, was isolated from Zephyranthes candida (Amaryllidaceae). The structure of 1 was elucidated by spectroscopic analyses and NMR calculation, and a plausible biogenetic pathway for zephycandidine A (1) was proposed. Zephycandidine A (1) exhibited significant cytotoxicity against five cancer cell lines with IC₅₀ values ranging from 1.98 to 7.03 μM with selectivity indices as high as 10 when compared to the normal Beas-2B cell. Further studies suggested that zephycandidine A (1) induces apoptosis in leukemia cells by the activation of caspase-3, upregulation of Bax, downregulation of Bcl-2, and degradation of PARP expression. In addition, zephycandidine A (1) showed acetylcholinesterase (AChE) inhibitory activity, and the docking studies of zephycandidine A (1) and galanthamine (2) with AChE revealed that interactions with W286 and Y337 are necessary.