Neuroprotective activity and acetylcholinesterase inhibition of five Amaryllidaceae species: A comparative study

Harnessing the power of natural alkaloids: the emergent role in epilepsy therapy

The quest for effective epilepsy treatments has spotlighted natural alkaloids due to their broad neuropharmacological effects. This review provides a comprehensive analysis of the antiseizure properties of various natural compounds, with an emphasis on their mechanisms of action and potential therapeutic benefits. Our findings reveal that bioactive substances such as indole, quinoline, terpenoid, and pyridine alkaloids confer medicinal benefits by modulating synaptic interactions, restoring neuronal balance, and mitigating neuroinflammation-key factors in managing epileptic seizures. Notably, these compounds enhance GABAergic neurotransmission, diminish excitatory glutamatergic activities, particularly at NMDA receptors, and suppress proinflammatory pathways. A significant focus is placed on the strategic use of nanoparticle delivery systems to improve the solubility, stability, and bioavailability of these alkaloids, which helps overcome the challenges associated with crossing the blood-brain barrier (BBB). The review concludes with a prospective outlook on integrating these bioactive substances into epilepsy treatment regimes, advocating for extensive research to confirm their efficacy and safety. Advancing the bioavailability of alkaloids and rigorously assessing their toxicological profiles are essential to fully leverage the therapeutic potential of these compounds in clinical settings.

Influence of Sucrose and Activated Charcoal on Phytochemistry and Vegetative Growth in Zephyranthes irwiniana (Ravenna) Nic. García (Amaryllidaceae)

Zephyranthes irwiniana (Ravenna) Nic. García is an endemic, red list threatened species from the Brazilian savanna (Cerrado) with pharmacological potential to treat the symptoms of Alzheimer's Disease (AD). This work analyzed the vegetative growth and phytochemistry of its potential compounds, in response to variations in sucrose concentration and activated carbon (AC). Seeds were germinated in vitro and in the greenhouse. The in vitro bulbs were separated in six treatments with different sucrose concentrations (30, 45 and 60 gL-1) and/or AC (1 gL-1). Biomass increases in individuals grown in the greenhouse were higher than those cultivated in vitro. Sucrose concentration significantly increased biomass and root number. AC had a positive influence on leaf and root size, and a negative influence on root number. GC-MS analyses indicated great variation in the abundance of α-terpenyl-acetate, ethyl linoleate, clionasterol and lycorine between treatments, with maximum concentrations of 53.06%, 38.68, 14.34% and 2.57%, respectively. Histolocalization tests indicated the presence of alkaloids in the leaf chlorenchyma and bulb cataphylls. Finally, the present study provided new evidence that the constitution of the culture medium directly influences the vegetative growth and phytochemistry of this species, providing a good medium condition for propagating the species under threat.

Pharmacological and toxicological effects of Amaryllidaceae

The Amaryllidaceae family is widely distributed in the tropics, presenting biological activity attributed mostly to alkaloids, such as an important inhibitory activity of acetylcholinesterase (AChE), antifungal, antibacterial, and cytotoxic activities. The present study aims to review the spectrum of action of the main biological activities and toxicity of secondary metabolites found in Amaryllidaceae through a literature review, using Prisma and the descriptors "Pharmacological effects of Amaryllidaceae" and "Amaryllidaceae family" and "Pharmacological actions of Amaryllidaceae", used in English and Portuguese. The literature search was done in March and May 2023. Original works published from 2012 to 2023, available in full, and presenting experimental and clinical studies were included. After the selection considering the inclusion and exclusion criteria, 60 articles fulfilled the defined criteria. From a pharmacological point of view, the highlight is due to the alkaloid galantamine, which has the potential- and is already used - for treating Alzheimer's. The toxicological aspect must be considered and evaluated carefully, as alkaloids have been associated with adverse effects such as nausea, vomiting, diarrhea, abdominal pain, and cardiovascular, neurological, and respiratory changes. Furthermore, some studies indicate that consuming these plants in significant quantities can lead to hepatic and renal toxicity. Therefore, the therapeutical use of this family's plant drugs and derivatives requires further studies to elucidate its effects and point out metabolites with therapeutic potential.

Natural compounds as lactate dehydrogenase inhibitors: potential therapeutics for lactate dehydrogenase inhibitors-related diseases

Lactate dehydrogenase (LDH) is a crucial enzyme involved in energy metabolism and present in various cells throughout the body. Its diverse physiological functions encompass glycolysis, and its abnormal activity is associated with numerous diseases. Targeting LDH has emerged as a vital approach in drug discovery, leading to the identification of LDH inhibitors among natural compounds, such as polyphenols, alkaloids, and terpenoids. These compounds demonstrate therapeutic potential against LDH-related diseases, including anti-cancer effects. However, challenges concerning limited bioavailability, poor solubility, and potential toxicity must be addressed. Combining natural compounds with LDH inhibitors has led to promising outcomes in preclinical studies. This review highlights the promise of natural compounds as LDH inhibitors for treating cancer, cardiovascular, and neurodegenerative diseases.

Cytotoxic Activity of Amaryllidaceae Plants against Cancer Cells: Biotechnological, In Vitro, and In Silico Approaches

Cancer is a major cause of death and an impediment to increasing life expectancy worldwide. With the aim of finding new molecules for chemotherapeutic treatment of epidemiological relevance, ten alkaloid fractions from Amaryllidaceae species were tested against six cancer cell lines (AGS, BT-549, HEC-1B, MCF-7, MDA-MB 231, and PC3) with HaCat as a control cell line. Some species determined as critically endangered with minimal availability were propagated using in vitro plant tissue culture techniques. Molecular docking studies were carried out to illustrate binding orientations of the 30 Amaryllidaceae alkaloids identified in the active site of some molecular targets involved with anti-cancer activity for potential anti-cancer drugs. In gastric cancer cell line AGS, the best results (lower cell viability percentages) were obtained for Crinum jagus (48.06 ± 3.35%) and Eucharis bonplandii (45.79 ± 3.05%) at 30 µg/mL. The research focused on evaluating the identified alkaloids on the Bcl-2 protein family (Mcl-1 and Bcl-xL) and HK2, where the in vitro, in silico and statistical results suggest that powelline and buphanidrine alkaloids could present cytotoxic activity. Finally, combining experimental and theoretical assays allowed us to identify and characterize potentially useful alkaloids for cancer treatment.

Neuroprotective activity of novel phenanthrene derivative from Grewia tiliaefolia by in vitro and in silico studies

Medicinal plants possess range of phytochemicals accountable for their diverse biological activities. Presently, such compounds have been isolated from medicinal plants, characterized and evaluated for their pharmacological potential. In the present study, the efforts have been made to isolate the compound(s) from Grewia tiliaefolia Vahl., plant known for its ameliorative effect on brain related diseases such as anxiety, depression, cognitive disorders and Parkinson's disease. Plant extract was subjected to isolation of compound(s) using column chromatography and isolated compound was characterized by NMR FTIR and LCMS. The isolated compound was novel with the IUPAC name of the compound is propyl 3-hydroxy-10,13-dimethyl-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthrene-17-carboxylate, designated as A-1 and has not been reported before. A-1 was further evaluated for its antioxidant potential using in vitro antioxidant assays (2,2-diphenyl-1-picryl-hydrazyl-hydrate, DPPH assay and reducing power assay, RPA). Also, Acetylcholinesterase (AChE) inhibitory potential of A-1 and extract was analysed. Results showed that A-1 exhibited significantly higher antioxidant activity in both DPPH and RPA assay as compared to plant extract. In case of AChE inhibitory activity again, A-1 has shown significantly higher activity as compared to plant extract. In silico study was conducted to predict its action on proteins playing crucial role in neurological and neurodegenerative disorders such as gamma amino butyric acid (GABA) receptor and glutamate α amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (Glu AMPA) receptor in epilepsy and AChE enzyme in Alzheimer's diseases. The compound has shown interaction in following order: AChE > GABA receptor > Glu AMPA receptor. Further, molecular dynamic simulations and ADME studies of A-1 and AChE enzyme revealed that A-1 yielded good results in all parameters and hence can relieve Alzheimer's like symptoms.

A Comparative Study between Lycorine and Galantamine Abilities to Interact with AMYLOID β and Reduce In Vitro Neurotoxicity

Galantamine is a natural alkaloid extracted from the Amaryllidaceae plants and is used as the active ingredient of a drug approved for the treatment of the early stages of Alzheimer's disease. It mainly acts as an acetylcholinesterase (AChE) inhibitor, increasing concentrations of the acetylcholine neurotransmitter. Recent cellular studies have also shown the ability of galantamine to protect SH-SY5Y cell lines against amyloid-β (Aβ)-induced toxicity. Such investigations have supported and validated further in-depth studies for understanding the chemical and molecular features associated with galantamine-protective abilities. In addition to galantamine, other natural alkaloids are known to possess AChE inhibitory activity; among them lycorine has been extensively investigated for its antibacterial, anti-inflammatory and antitumoral activities as well. Despite its interesting biological properties, lycorine's neuroprotective functions against Aβ-induced damages have not been explored so far. In this research study, the ability of galantamine and lycorine to suppress Aβ-induced in vitro neuronal toxicity was evaluated by investigating the chemical interactions of the two alkaloids with Aβ peptide. A multi-technique spectroscopic analysis and cellular cytotoxicity assays were applied to obtain new insights on these molecular associations. The comparison between the behaviors exhibited by the two alkaloids indicates that both compounds possess analogue abilities to interact with the amyloidogenic peptide and protect cells.

Bioactive compounds by microalgae and potentials for the management of some human disease conditions

Microalgae biomasses are excellent sources of diverse bioactive compounds such as lipids, polysaccharides, carotenoids, vitamins, phenolics and phycobiliproteins. Large-scale production of these bioactive substances would require microalgae cultivation either in open-culture systems or closed-culture systems. Some of these bioactive compounds (such as polysaccharides, phycobiliproteins and lipids) are produced during their active growth phase. They appear to have antibacterial, antifungal, antiviral, antioxidative, anticancer, neuroprotective and chemo-preventive activities. These properties confer on microalgae the potential for use in the treatment and/or management of several neurologic and cell dysfunction-related disease conditions, including Alzheimer's disease (AD), AIDS and COVID-19, as shown in this review. Although several health benefits have been highlighted, there appears to be a consensus in the literature that the field of microalgae is still fledgling, and more research needs to be carried out to ascertain the mechanisms of action that underpin the effectiveness of microalgal compounds. In this review, two biosynthetic pathways were modeled to help elucidate the mode of action of the bioactive compounds from microalgae and their products. These are carotenoid and phycobilin proteins biosynthetic pathways. The education of the public on the importance of microalgae backed with empirical scientific evidence will go a long way to ensure that the benefits from research investigations are quickly rolled out. The potential application of these microalgae to some human disease conditions was highlighted.

Chemical Survey of Three Species of the Genus Rauhia Traub (Amaryllidaceae)

Plant biodiversity is an important source of compounds with medicinal properties. The alkaloid galanthamine, first isolated from Galanthus woronowii (Amaryllidaceae), is approved by the FDA for the palliative treatment of mild to moderate Alzheimer's disease due to its acetylcholinesterase (AChE) inhibitory activity. Obtaining this active pharmaceutical ingredient, still sourced on an industrial scale from the Amaryllidaceae species, is a challenge for pharmaceutical companies due to its low natural yield and the high cost of its synthesis. The aim of this work was to determine the alkaloid profile of three different Rauhia (Amaryllidaceae) species collected in Peru, and to assess the potential application of their extracts for the treatment of Alzheimer's disease. The alkaloids were identified by gas chromatography coupled to mass spectrometry (GC-MS), and the AChE inhibitory activity of the extracts was analyzed. Thirty compounds were quantified from the Rauhia species, the R. multiflora extract being the most interesting due to its high diversity of galanthamine-type structures. The R. multiflora extract was also the most active against AChE, with the half maximal inhibitory concentration (IC₅₀) values of 0.17 ± 0.02 μg·mL^-1 in comparison with the IC₅₀ values of 0.53 ± 0.12 μg·mL^-1 for galanthamine, used as a reference. Computational experiments were carried out on the activity of the galanthamine-type alkaloids identified in R. multiflora toward five different human AChE structures. The simulation of the molecules 3-O-acetylgalanthamine, 3-O-acetylsanguinine, narwedine, and lycoraminone on the 4EY6 crystal structure theoretically showed a higher inhibition of hAChE and different interactions with the active site compared to galanthamine. In conclusion, the results of this first alkaloid profiling of the Rauhia species indicate that R. multiflora is an important natural source of galanthamine-type structures and could be used as a model for the development of biotechnological tools necessary to advance the sustainable production of galanthamine.

Novel Multipotent Amantadine-M30D Hybrids with Highly Selective Butyrylcholinesterase Inhibition and Neuroprotective Effects as Effective Anti-Alzheimer's Agents

As a contribution to the development of new dual/multifunctional drugs, a novel therapeutical scaffold merging key structural features from memantine and M30D was designed, synthesized, and explored for its AChE/BuChE inhibitory activity and neuroprotective effects. All synthetized hybrids were not able to inhibit AChE, but most of them exhibit inhibition with high selectivity toward butyrylcholinesterase (BuChE). Notably, among the tested compounds, amantadine/M30D hybrids with six, seven, nine, and twelve methylene groups in the spacer (5d, 5e, 5f, and 5g) not only highlighted having the best potency and selective butyrylcholinesterase inhibition greater than 83% but also, particularly 5e and 5d, elicited considerable neuroprotection when evaluated in pretreatment conditions, by reducing injury effects caused by glutamate with maximum protection reached about 47.82 ± 0.81% (5e) and 42 ± 2.20% (5d) in comparison with memantine (37.27 ± 2.69%). Likewise, we chose 5e as the hit compound, which in a glutamate excitotoxity coculture model prevented astroglia reactivity and neuronal death, as well as a 91% restoration of calcium levels and an increasing ATP level in both pre-/post-treatments of 61.48 ± 4.60 and 45.16 ± 10.55%, respectively. Regarding docking studies, a blockade of the NMDA channel pore by 5e would explain its neuroprotective response. Finally, the hit compound 5e exhibited in vitro blood-brain barrier (BBB) permeability and human plasma stability, as well as an optimal in silico neuropharmacokinetic profile. From a therapeutic perspective, merging key pharmacophoric features from memantine and M30D provides a new medicinal scaffold with dual-/multifunctional properties and human plasma stability for the future development of potential drugs for treating AD.

In vitro and in silico analysis of galanthine from Zephyranthes carinata as an inhibitor of acetylcholinesterase

Zephyranthes carinata Herb., a specie of the Amaryllidoideae subfamily, has been reported to have inhibitory activity against acetylcholinesterase. However, scientific evidence related to their bioactive alkaloids has been lacking. Thus, this study describes the isolation of the alkaloids of this plant, and their inhibition of the enzymes acetylcholinesterase (eeAChE) and butyrylcholinesterase (eqBuChE), being galanthine the main component. Additionally, haemanthamine, hamayne, lycoramine, lycorine, tazettine, trisphaeridine and vittatine/crinine were also isolated. The results showed that galanthine has significant activity at low micromolar concentrations for eeAChE (IC₅₀ = 1.96 μg/mL). The in-silico study allowed to establish at a molecular level the high affinity and the way galanthine interacts with the active site of the TcAChE enzyme, information that corroborates the result of the experimental IC₅₀. However, according to molecular dynamics (MD) analysis, it is also suggested that galanthine presents a different inhibition mode that the one observed for galanthamine, by presenting interaction with peripheral anionic binding site of the enzyme, which prevents the entrance and exit of molecules from the active site. Thus, in vitro screening assays plus rapid computer development play an essential role in the search for new cholinesterase inhibitors by identifying unknown bio-interactions between bioactive compounds and biological targets.

Crinum jagus (J. Thomps. Dandy): Antioxidant and protective properties as a medicinal plant on toluene-induced oxidative stress damages in liver and kidney of rats

Crinum jagus (C. jagus; J. Thomps.) Dandy (Liliaceae) is a pantropical plant known for its medicinal values and pharmacological properties. The study assessed the protective effects and changes in oxidative stress indices due to C. jagus leaf extracts on the toluene-induced liver and kidney injuries in rats. The study was conducted on 8-week-old male Wistar rats (n = 80), weighing 243.3 ± 1.42 g. Group I, 1 ml/kg distilled water for 7 days; Group II, 4.5 ml/kg toluene once, 1 ml/kg distilled water for 7 days; Group III, 4.5 ml/kg toluene once, 500 mg/kg methanolic extract for 7 days; Group IV, 4.5 ml/kg toluene once, 500 mg/kg aqueous extract for 7 days; Group V, 500 mg/kg methanolic extract for 7 days; Group VI, 500 mg/kg aqueous extract for 7 days; Group VII, 500 mg/kg of vitamin C for 7 days; Group, VIII, 4.5 ml/kg toluene once, 500 mg/kg vitamin C for 7 days, all administrations were given by oral gavage. The phytochemical contents, absolute and relative organ weights of liver and kidneys, liver and kidney function tests, antioxidant status, as well as histological tests were analyzed using standard protocols. The tannins, flavonoids, and polyphenols were in highest concentration in both extracts, content in methanol extract (57.04 ± 1.51 mgg-1, 35.43 ± 1.03 mgg-1, 28.2 ± 0.34 mgg-1 respectively) > aqueous extract (18.74 ± 1.01 mgg-1, 13.43 ± 0.47 mgg-1, 19.65 ± 0.21 mgg-1 respectively). In the negative control group (II), bodyweights significantly (P < 0.05) reduced by 22%, liver weight and kidney weight significantly (P < 0.05) increased by 42% and 83% respectively, liver-to-bodyweight and kidney-to-bodyweight ratios increased significantly (P < 0.05); serum liver function tests (LFTs) i.e., bilirubin, alkaline phosphatase (ALP), Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Gamma-glutamyl transferase (GGT), and serum kidney function tests (creatinine and urea) were significantly (P < 0.05) elevated; oxidant status (tissue malondialdehyde; MDA) was significantly (P < 0.05) elevated, antioxidant status i.e., tissue superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels was significantly (P < 0.05) reduced; with markedly visible renal and hepatic histopathological findings, compared to the normal control group. In C. jagus extract test groups (III and IV), the parameters were significantly (P < 0.05) alleviated and reversed to normal/near normal compared to the negative control. The LFTs, kidney function tests, and antioxidant status were significantly (P < 0.05) more improved with the methanol extract test and standard control groups compared to the aqueous extract test group; Also, the methanol extract test group showed better histological features than the aqueous extract test and standard control groups. The methanolic extract shows better antioxidant potential due to the availability of more nonenzymatic antioxidants (tannins, flavonoids, and polyphenols). The findings showed that toluene is a very aggressive xenobiotic due to the promotion of oxidative stress and peroxidation of cellular lipids, but C. jagus leaves provide significant protection through the reducing power of nonenzymatic antioxidants and their ability to induce endogenous antioxidant enzymes (SOD, CAT, and glutathione reductase or GR) causing reduced cellular lipid peroxidation and tissue damages, quickened tissue repair, and improved cell biology of liver and kidneys during toluene toxicity. The methanol leaf extract provides better protection and should be advanced for more experimental and clinical studies to confirm its efficacy in alleviating oxidative stress tissue injuries, specifically due to toluene.

Lycorine improves peripheral nerve function by promoting Schwann cell autophagy via AMPK pathway activation and MMP9 downregulation in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes mellitus and no effective therapy is approved. Here, lycorine, a natural alkaloid, was identified as a potential drug for DPN by the bioinformatics analysis of GEO datasets and Connectivity Map database. Lycorine administration improved peripheral nerve function and autophagy-associated proteins of diabetic mice. Again, in vitro high glucose-cultured rat Schwann cells (RSC96) showed enhanced autophagosome marker LC3-II with the treatment of lycorine. Additionally, beclin-1 and Atg3 were decreased in high glucose-stimulated RSC96 cells, which were reversed by lycorine treatment. Furthermore, DPN-associated differentially expressed genes (DEGs) from GEO datasets and lycorine-drug targets from PubChem and PharmMapper were visually analyzed and revealed that MMP9 was both DPN-associated DEGs and lycorine-drug target. Functional enrichment analysis of MMP9-relevant genes showed that cell energy metabolism was involved. Moreover, lycorine reduced high glucose-enhanced MMP9 expression in RSC96 cells. Overexpression of MMP9 attenuated lycorine-induced the expression of beclin-1, Atg3 and LC3-II in high glucose-cultured RSC96 cells. In addition, AMPK pathway activation was confirmed in lycorine-treated high glucose-cultured RSC96 cells. Then AMPK pathway inhibition attenuated lycorine-reduced MMP9 expression in high glucose-treated RSC96 cells. Molecular docking analysis revealed that lycorine bound the domain of AMPK containing Thr 172 site, which affected AMPK (Thr 172) phosphorylation. Finally, AMPK pathway activation and MMP9 downregulation were also revealed in the sciatic nerves of diabetic mice administrated with lycorine. Taken together, lycorine was advised to promote Schwann cell autophagy via AMPK pathway activation and MMP9 downregulation-induced LC3-II transformation in diabetic peripheral neuropathy.

Alkaloid Profiling and Cholinesterase Inhibitory Potential of Crinum × amabile Donn. (Amaryllidaceae) Collected in Ecuador

Natural products are one of the main sources for developing new drugs. The alkaloids obtained from the plant family Amaryllidaceae have interesting structures and biological activities, such as acetylcholinesterase inhibition potential, which is one of the mechanisms used for the palliative treatment of Alzheimer's disease symptoms. Herein we report the alkaloidal profile of bulbs and leaves extracts of Crinum × amabile collected in Ecuador and their in vitro inhibitory activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. Using Gas Chromatography coupled to Mass Spectrometry (GC-MS), we identified 12 Amaryllidaceae alkaloids out of 19 compounds detected in this species. The extracts from bulbs and leaves showed great inhibitory activity against AChE and BuChE, highlighting the potential of Amaryllidaceae family in the search of bioactive molecules.

Dihydrolycorine Attenuates Cardiac Fibrosis and Dysfunction by Downregulating Runx1 following Myocardial Infarction

In spite of early interventions to treat acute myocardial infarction (MI), the occurrence of adverse cardiac remodeling following heart failure due to acute MI remains a clinical challenge. Thus, there is an increasing demand for the development of novel therapeutic agents capable of inhibiting the development of pathological ventricular remodeling. RNA-seq data analysis of acute MI rat models from GEO revealed that Runx1 was the most differentially expressed MI-related gene. In this study, we demonstrated that increased Runx1 expression under pathological conditions results in decreased cardiac contractile function. We identified dihydrolycorine, an alkaloid lycorine, as a promising inhibitor of Runx1. Our results showed that treatment with this drug could prevent adverse cardiac remodeling, as indicated by the downregulation of fibrotic genes using western blotting (collagen I, TGFβ, and p-smad3), downregulation of the apoptosis gene Bax, upregulation of the apoptosis gene Bcl-2, and improved cardiac functions, such as LVEF, LVSF, LVESD, and LVEDD. Additionally, dihydrolycorine treatment could rescue cardiomyocyte hypertrophy as demonstrated by wheat germ agglutinin staining, increased expression levels of the punctuate gap junction protein connexin 43, and decreased α-SMA expression, resulting in cardiomyocyte fibrosis in immunofluorescence staining. Molecular docking, binding modeling, and pull-down assays were used to identify potential dihydrolycorine-binding sites in Runx1. When Ad-sh-Runx1 was transfected into hypoxia-cardiomyocytes or injected into the hearts of MI rats, the cardioprotective effects of dihydrolycorine were abolished, and the normal electrophysiological activity of cardiomyocytes was disrupted. Taken together, the results of the present study indicate that dihydrolycorine may inhibit adverse cardiac remodeling after MI through the reduction of Runx1, suggesting that dihydrolycorine-mediated-Runx1 regulation might represent a novel therapeutic approach for adverse cardiac remodeling after MI.

Structural Diversity and Biological Potential of Alkaloids from the Genus Hippeastrum, Amaryllidaceae: an Update

The subfamily Amaryllidoideae, Amaryllidaceae, presents an exclusive group of structures known as Amaryllidaceae alkaloids, which have a broad spectrum of biological activities. These plants are classified into 59 genera, including Hippeastrum Herb., which comprises approximately 60 species distributed mainly in South America, being widely used as ornamental plants due to the beauty of its flowers. This review presents an update about the alkaloid profiling of Hippeastrum extracts published between 2012 and 2021, as well as an approach to the biological potential of these compounds.

Recent Progress on Biological Activity of Amaryllidaceae and Further Isoquinoline Alkaloids in Connection with Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive age-related neurodegenerative disease recognized as the most common form of dementia among elderly people. Due to the fact that the exact pathogenesis of AD still remains to be fully elucidated, the treatment is only symptomatic and available drugs are not able to modify AD progression. Considering the increase in life expectancy worldwide, AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. Due to their complex nitrogen-containing structures, alkaloids are considered to be promising candidates for use in the treatment of AD. Since the introduction of galanthamine as an antidementia drug in 2001, Amaryllidaceae alkaloids (AAs) and further isoquinoline alkaloids (IAs) have been one of the most studied groups of alkaloids. In the last few years, several compounds of new structure types have been isolated and evaluated for their biological activity connected with AD. The present review aims to comprehensively summarize recent progress on AAs and IAs since 2010 up to June 2021 as potential drugs for the treatment of AD.

Potential therapeutic natural products against Alzheimer's disease with Reference of Acetylcholinesterase

Alzheimer's disease (AD), is the most common type of dementia primarily affecting the later years of life. Its prevalence is likely to increase in any aging population and will be a major burden on healthcare system by the mid of the century. Despite scientific and technological breakthroughs in the last 50 years, that have expanded our understanding of the disease on a system, cellular and molecular level, therapies that could stop or slow the progression of the disease are still unavailable. The Food and Drug Administration (FDA), has approved acetylcholinesterase (AChE) inhibitors (donepezil, galantamine, tacrine and rivastigmine) and glutamate receptor antagonist (memantine) for the treatment of AD. In this review we summarize the studies reporting phytocompounds and extracts from medicinal plants that show AChE inhibitory activities and could be of potential benefit in AD. Future research directions are suggested and recommendations made to expand the use of medicinal plants and their formulations to prevent, mitigate and treat AD.

Palladium-mediated synthesis and biological evaluation of C-10b substituted Dihydropyrrolo[1,2-b]isoquinolines as antileishmanial agents

The development of new molecules for the treatment of leishmaniasis is, a neglected parasitic disease, is urgent as current anti-leishmanial therapeutics are hampered by drug toxicity and resistance. The pyrrolo[1,2-b]isoquinoline core was selected as starting point, and palladium-catalyzed Heck-initiated cascade reactions were developed for the synthesis of a series of C-10 substituted derivatives. Their in vitro leishmanicidal activity against visceral (L. donovani) and cutaneous (L. amazonensis) leishmaniasis was evaluated. The best activity was found, in general, for the 10-arylmethyl substituted pyrroloisoquinolines. In particular, 2ad (IC₅₀ = 3.30 μM, SI > 77.01) and 2bb (IC₅₀ = 3.93 μM, SI > 58.77) were approximately 10-fold more potent and selective than the drug of reference (miltefosine), against L. amazonensis on in vitro promastigote assays, while 2ae was the more active compound in the in vitro amastigote assays (IC₅₀ = 33.59 μM, SI > 8.93). Notably, almost all compounds showed low cytotoxicity, CC₅₀ > 100 μg/mL in J774 cells, highest tested dose. In addition, we have developed the first Perturbation Theory Machine Learning (PTML) algorithm able to predict simultaneously multiple biological activity parameters (IC₅₀, K_i, etc.) vs. any Leishmania species and target protein, with high values of specificity (>98%) and sensitivity (>90%) in both training and validation series. Therefore, this model may be useful to reduce time and assay costs (material and human resources) in the drug discovery process.

CDK5 Targeting as a Therapy for Recovering Neurovascular Unit Integrity in Alzheimer's Disease

The neurovascular unit (NVU) is responsible for synchronizing the energetic demand, vasodynamic changes, and neurochemical and electrical function of the brain through a closed and interdependent interaction of cell components conforming to brain tissue. In this review, we will focus on cyclin-dependent kinase 5 (CDK5) as a molecular pivot, which plays a crucial role in the healthy function of neurons, astrocytes, and the endothelium and is implicated in the cross-talk of cellular adhesion signaling, ion transmission, and cytoskeletal remodeling, thus allowing the individual and interconnected homeostasis of cerebral parenchyma. Then, we discuss how CDK5 overactivation affects the integrity of the NVU in Alzheimer's disease (AD) and cognitive impairment; we emphasize how CDK5 is involved in the excitotoxicity spreading of glutamate and Ca2+ imbalance under acute and chronic injury. Additionally, we present pharmacological and gene therapy strategies for producing partial depletion of CDK5 activity on neurons, astrocytes, or endothelium to recover neuroplasticity and neurotransmission, suggesting that the NVU should be the targeted tissue unit in protective strategies. Finally, we conclude that CDK5 could be effective due to its intervention on astrocytes by its end feet on the endothelium and neurons, acting as an intermediary cell between systemic and central communication in the brain. This review provides integrated guidance regarding the pathogenesis of and potential repair strategies for AD.

Acetylcholinesterase inhibitory activity, anti-inflammatory, and neuroprotective potential of Hippeastrum psittacinum (Ker Gawl.) herb (Amaryllidaceae)

Hippeastrum psittacinum, Amaryllidaceae, is used in traditional medicine as a purgative, aphrodisiac, and anticough remedy. The ethanol extract (EE) and alkaloid-rich fractions (ARF) from H. psittacinum bulbs were evaluated for their acetylcholinesterase (AChE) inhibition. The EE cytotoxic and anti-inflammatory effects in RAW 264.7 cells, and the neuroprotective and genotoxic activities in SH-SY5Y cells, were also estimated. Fifteen alkaloids were identified in the EE by gas chromatography-mass spectrometry. ARFs were less active for AChE inhibition than EE. The viability of both cell lines was higher than 70% with EE concentrations below 25 μg/mL. The EE decreased nitrite release in RAW cells stimulated with lipopolysaccharide, showing values of 83, 67, and 53% at 6.25, 12.5, and 25 μg/mL, respectively. Furthermore, the EE partially protected SH-SY5Y cells from hydrogen peroxide-mediated deleterious effects by approximately 50% at the same concentrations. The micronucleus assays showed that the extract caused chromosomal missegregation at concentrations above 12.5 μg/mL. The in silico analyses showed that some alkaloids presented properties of permeation of the blood-brain barrier and the intestine. Our findings present new evidence of the potential of H. psittacinum potential as an AChE inhibitor, as well as an anti-inflammatory and neuroprotective agent.

Construction of Various Bridged Polycyclic Skeletons by Palladium-Catalyzed Dearomatization

A powerful palladium-catalyzed dearomative cyclization was developed that provides facile access to eight types of bridged tetracyclic skeletons bearing various ring sizes and heterocycles. With this method, several skeletons or analogues of natural products, including tubingensin B and dracaenones, were synthesized. Asymmetric dearomative cyclization enables the construction of various enantiomerically enriched bridged polycyclic systems with up to 99 % ee by employing a chiral palladium catalyst.

Natural Compound Library Screening Identifies New Molecules for the Treatment of Cardiac Fibrosis and Diastolic Dysfunction

BACKGROUND

Myocardial fibrosis is a hallmark of cardiac remodeling and functionally involved in heart failure development, a leading cause of deaths worldwide. Clinically, no therapeutic strategy is available that specifically attenuates maladaptive responses of cardiac fibroblasts, the effector cells of fibrosis in the heart. Therefore, our aim was to develop novel antifibrotic therapeutics based on naturally derived substance library screens for the treatment of cardiac fibrosis.

METHODS

Antifibrotic drug candidates were identified by functional screening of 480 chemically diverse natural compounds in primary human cardiac fibroblasts, subsequent validation, and mechanistic in vitro and in vivo studies. Hits were analyzed for dose-dependent inhibition of proliferation of human cardiac fibroblasts, modulation of apoptosis, and extracellular matrix expression. In vitro findings were confirmed in vivo with an angiotensin II-mediated murine model of cardiac fibrosis in both preventive and therapeutic settings, as well as in the Dahl salt-sensitive rat model. To investigate the mechanism underlying the antifibrotic potential of the lead compounds, treatment-dependent changes in the noncoding RNAome in primary human cardiac fibroblasts were analyzed by RNA deep sequencing.

RESULTS

High-throughput natural compound library screening identified 15 substances with antiproliferative effects in human cardiac fibroblasts. Using multiple in vitro fibrosis assays and stringent selection algorithms, we identified the steroid bufalin (from Chinese toad venom) and the alkaloid lycorine (from Amaryllidaceae species) to be effective antifibrotic molecules both in vitro and in vivo, leading to improvement in diastolic function in 2 hypertension-dependent rodent models of cardiac fibrosis. Administration at effective doses did not change plasma damage markers or the morphology of kidney and liver, providing the first toxicological safety data. Using next-generation sequencing, we identified the conserved microRNA 671-5p and downstream the antifibrotic selenoprotein P1 as common effectors of the antifibrotic compounds.

CONCLUSIONS

We identified the molecules bufalin and lycorine as drug candidates for therapeutic applications in cardiac fibrosis and diastolic dysfunction.

In vitro micropropagation and alkaloids analysis by GC-MS of Chilean Amaryllidaceae plants: Rhodophiala pratensis

INTRODUCTION

Plants from Amaryllidaceae family are of interest since they produce a particular type of alkaloid useful for the treatment of neurodegenerative diseases of the central nervous system, such as Galanthamine. Given the low content of these secondary metabolites in the plant, it is necessary to study mechanisms to increase the productivity of them.

OBJECTIVE

To obtain fast qualitative and quantitative analysis of the alkaloids and extend the understanding of biosynthesis and metabolism in these kinds of plants. Furthermore, establish a reliable, simple and fast analytical method for the in vitro callus culture of vegetative organs for Rhodophiala pratensis species.

METHODS

The alkaloids composition of the callus culture of R. pratensis were analysed by gas chromatography coupled with mass spectrometry (GC-MS).

RESULTS

A methodology for the qualitative and quantitative analysis of the alkaloids present in fresh callus culture of this wild plant species was established. The analysis showed alternation in the alkaloids type ratio and number of compounds between wild bulbs, in vitro bulbs and callus. It was possible to identify 24 alkaloids from a pool of 60 signals whose fragmentation pattern corresponds to the alkaloids of Amaryllidaceae plants. Together with the aforementioned, the amount and type of alkaloid present in the plant material obtained by in vitro culture of R. pratensis was determined in the same way. The results show the high biosynthetic potential of in vitro grown bulbs and callus tissue that are able to produce significant amounts of pharmacologically relevant alkaloids from R. pratensis in various proportions that depend on the culture conditions such as supplementation with growth substances. The in vitro grown bulbs produce an alkaloidal extract that contain a 52.6% w/w of alkaloids.

CONCLUSION

This study allowed the alkaloid content in callus culture of R. pratensis to be found by means of GC-MS. These results allowed a relationship between the type of growth regulator and the type of alkaloids found to be established. Finally, we can say that the results achieved to state that the production of alkaloids using different combinations of growth regulators could be directed during in vitro micropropagation from provided plant material.

An In Vitro and In Vivo Cholinesterase Inhibitory Activity of Pistacia khinjuk and Allium sativum Essential Oils

Objectives

Alzheimer’s disease (AD), an overwhelming neurodegenerative disease, has deleterious effects on the brain that consequently causes memory loss and language impairment. This study was intended to investigate the neuroprotective activity of the two essential oils (EOs) from Iranian Pistacia khinjuk (PK) leaves and Allium sativum (AS) cloves against β-Amyloid 25–35 (Aβ25-35) induced elevation of cholinesterase enzymes in AD.

Methods

The EOs of PK (PKEO) and AS (ASEO) were prepared and analyzed in terms of extraction yield, phenolic content, and cholinergic markers in vitro. Moreover, both were administered orally to adult male Wistar rats at concentrations of 1, 2, and 3%. The inhibitory potential of PKEO and ASEO was compared with Donepezil (0.75 mg/kg) against the high activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes.

Results

PKEO reached an inhibition rate of 83.6% and 81.4% against AChE and BChE, respectively. ASEO had lower anti-cholinesterase activity (65.4% and 31.5% for the inhibition AChE and BChE). PKEO was found to have more phenolic content than ASEO. A significantly positive correlation was observed between the total phenolics and anti-cholinesterase potential. In rats, both EOs decreased the enzyme activity in a concentration-dependent manner. As compared with Donepezil, the significant difference in the AChE and BChE inhibition occurred as rats were treated with PKEO 3% (p < 0.05).

Conclusion

It could be concluded that PKEO and ASEO are potent inhibitors of AChE and BChE in rats that hold promise to be used for the treatment of AD.

Application of Electrocyclic Ring-Opening and Desymmetrizing Nucleophilic Trappings of meso-6,6-Dibromobicyclo[3.1.0]hexanes to Total Syntheses of Crinine and Haemanthamine Alkaloids

The thermally induced electrocyclic ring-opening of C₂-symmetric ( meso) 6,6-dibromobicyclo[3.1.0]hexanes such as 10 in the presence of the chiral, nonracemic 1°-amine 28 afforded a ca. 1:1 mixture of the diastereoisomeric and chromatographically separable 1-amino-2-bromo-2-cyclohexenes 37 (42%) and 38 (45%). Each of these was elaborated over 13 steps, including Suzuki-Miyaura cross-coupling, radical cyclization, and Pictet-Spengler reactions, into (-)- or (+)-crinane (1 or ent-1, respectively). Variations on these protocols were applied to the total syntheses of (+)- and (-)-11-hydroxyvattitine [(+)- and (-)-3], (+)- and (-)-bulbispermine [(+)- and (-)-4], (+)- and (-)-haemanthamine [(+)- and (-)-5], (+)- and (-)-pretazettine [(+)- and (-)-6], and (+)- and (-)-tazettine [(+)- and (-)-7] as well as (±)-hamayne [(±)-8] and (±)-apohaemanthamine [(±)-9]. A number of these alkaloids were synthesized for the first time.

Neuroprotection and improvement of the histopathological and behavioral impairments in a murine Alzheimer's model treated with Zephyranthes carinata alkaloids

In Alzheimer's disease (AD), amyloid beta (Aβ) plaques initiates a cascade of pathological events where the overactivation of N-methyl-d-aspartate receptors (NMDA) by excess glutamate (Glu) triggers oxidative processes that lead to the activation of microglial cells, inflammation, and finally neuronal death. Amaryllidaceae alkaloids exert neuroprotective activities against different neurotoxin-induced injuries in vitro, and although their biological potential is well demonstrated, their neuroprotective activity has not been reported in an in vivo model of AD. The aim of our study was to determine the in vitro and in vivo neuroprotective potential of standardized alkaloidal fractions of Zephyranthes carinata. In this work, the neuroprotective effect of two alkaloidal fractions extracted from Z. carinata (bulbs and leaves) was analyzed in an in vitro excitotoxicity model in order to select the most promising one for subsequent evaluation in a triple transgenic mouse model of AD (3xTg-AD). We found that Z. carinata bulbs protect neurons against a Glu-mediated toxic stimulus in vitro, as evidenced by the decrease in apoptotic nuclei, the reduction in the lipid peroxidation product malondialdehyde and the conservation of dendritic structures. The effects of intraperitoneal administration of Z. carinata bulbs (10 mg/kg) every 12 h for 1 month on 3xTg-AD (18 months old) showed improved learning and spatial memory. Histopathologically, the alkaloidal fraction-treated 3xTg-AD mice exhibited a significant reduction in tauopathy and astrogliosis, as well as a significant decrease in the proinflammatory marker COX-2 and an increase in pAkt. The results suggest that Z. carinata bulbs provide neuroprotective effects both in vitro and in 3xTg-AD mice by intervening in the inflammatory processes, regulating the aggregation of pair helical filaments (PHFs) and activating survival pathways.

Naturally Occurring Acetylcholinesterase Inhibitors and Their Potential Use for Alzheimer's Disease Therapy

Alzheimer's disease (AD) is a main cause of dementia, accounting for up to 75% of all dementia cases. Pathophysiological processes described for AD progression involve neurons and synapses degeneration, mainly characterized by cholinergic impairment. This feature makes acetylcholinesterase inhibitors (AChEi) the main class of drugs currently used for the treatment of AD dementia phase, among which galantamine is the only naturally occurring substance. However, several plant species producing diverse classes of alkaloids, coumarins, terpenes, and polyphenols have been assessed for their anti-AChE activity, becoming potential candidates for new anti-AD drugs. Therefore, this mini-review aimed to recapitulate last decade studies on the anti-AChE activity of plant species, their respective extracts, as well as isolated compounds. The anti-AChE activity of extracts prepared from 54 plant species pertaining 29 families, as well as 36 isolated compounds were classified and discussed according to their anti-AChE pharmacological potency to highlight the most prominent ones. Besides, relevant limitations, such as proper antioxidant assessment, and scarcity of toxicological and clinical studies were also discussed in order to help researchers out with the bioprospection of potentially new AChEi.

A patent review of butyrylcholinesterase inhibitors and reactivators 2010-2017

INTRODUCTION

Butyrylcholinesterase (BuChE) has obtained a renewed interest as therapeutic target in Alzheimer's disease (AD), when changes in BuChE activity and expression along disease progression were highlighted as well as correlation between BuChE levels and cognitive function.

AREAS COVERED

During the last eight years, fourteen patents on BuChE inhibitors (BuChEI) have been submitted. Only three of them relate to BuChE selective inhibitors, while four of them focus on multitarget inhibitors which address different key pathological factors other than BuChE. Two patents report on non-selective acetylcholinesterase (AChE)/BuChE inhibitors, while four patents deal with natural compounds and their derivatives. One patent relates to antitoxic agents to treat exposure to ChEI pesticides and nerve agents.

EXPERT OPINION

Increasing evidence supports BuChE as a more beneficial target in moderate-to-severe forms of AD in comparison to the well-known AChE. However, hitting a single pathological target is likely not sufficient to halt the disease progression. Therefore, patented BuChE inhibitors with a multifunctional profile may open new therapeutic avenues, since the additional activities could reinforce the therapeutic effects. Unfortunately, in vivo studies are limited and key parameters, such as ADMET data, are missing. This lack of information makes difficult to forecast the development of patented BuChEIs into effective drug candidates.

Role of Plant Derived Alkaloids and Their Mechanism in Neurodegenerative Disorders

Neurodegenerative diseases are conventionally demarcated as disorders with selective loss of neurons. Conventional as well as newer molecules have been tested but they offer just symptomatic advantages along with abundant side effects. The discovery of more compelling molecules that can halt the pathology of these diseases will be considered as a miracle of present time. Several synthetic compounds are available but they may cause several other health issues. Therefore, natural molecules from the plants and other sources are being discovered to replace available medicines. In conventional medicational therapies, several plants have been reported to bestow remedial effects. Phytochemicals from medicinal plants can provide a better and safer alternative to synthetic molecules. Many phytochemicals have been identified that cure the human body from a number of diseases. The present article reviews the potential efficacy of plant-derived alkaloids, which possess potential therapeutic effects against several NDDs including Alzheimer's disease (AD), Huntington disease (HD), Parkinson's disease (PD), Epilepsy, Schizophrenia, and stroke. Alkaloids include isoquinoline, indole, pyrroloindole, oxindole, piperidine, pyridine, aporphine, vinca, β-carboline, methylxanthene, lycopodium, and erythrine byproducts. Alkaloids constitute positive roles in ameliorating pathophysiology of these illnesses by functioning as muscarinic and adenosine receptors agonists, anti-oxidant, anti-amyloid and MAO inhibitors, acetylcholinestrase and butyrylcholinesterase inhibitor, inhibitor of α-synuclein aggregation, dopaminergic and nicotine agonist, and NMDA antagonist.

Alkaloids of Amaryllidaceae as Inhibitors of Cholinesterases (AChEs and BChEs): An Integrated Bioguided Study

INTRODUCTION

Enzymatic inhibition of acetylcholinesterase (AChE) is an essential therapeutic target for the treatment of Alzheimer's disease (AD) and AChE inhibitors are the first-line drugs for it treatment. However, butyrylcholinesterase (BChE), contributes critically to cholinergic dysfunction associated with AD. Thus, the development of novel therapeutics may involve the inhibition of both cholinesterase enzymes.

OBJECTIVE

To evaluate, in an integrated bioguided study, cholinesterases alkaloidal inhibitors of Amaryllidaceae species.

METHODOLOGY

The proposed method combines high-performance thin-layer chromatography (HPTLC) with data analysis by densitometry, enzymatic bioautography with different AChEs and BChEs, the detection of bioactive molecules through gas chromatography mass spectrometry (GC-MS) analysis of spots of interest, and theoretical in silico studies.

RESULTS

To evaluate the bioguided method, the AChE and BChE inhibitory activities of seven Amaryllidaceae plant extracts were evaluated. The alkaloid extracts of Eucharis bonplandii exhibited a high level of inhibitory activity (IC₅₀  = 0.72 ± 0.05 μg/mL) against human recombinant AChE (hAChE). Regarding human serum BChE (hBChE), the bulb and leaf extracts of Crinum jagus had the highest activity (IC₅₀  = 8.51 ± 0.56 μg/mL and 11.04 ± 1.21 μg/mL, respectively). In the HPTLC spots with high inhibitory activity, several alkaloids were detected using GC-MS, and some of these alkaloids were identified. Galanthamine, galanthamine N-oxide and powelline should be the most prominent inhibitors of substrate accommodation in the active site of the Torpedo californica AChE (TcAChE), hAChE and hBChE enzymes.

CONCLUSIONS

These results are evidence of the chemical relevance of the Colombian's Amaryllidaceae species for the inhibition of cholinesterases and as potent sources for the palliative treatment of AD. Copyright © 2017 John Wiley & Sons, Ltd.

A Total Synthesis of (±)-3-O-Demethylmacronine through Rearrangement of a Precursor Embodying the Haemanthidine Alkaloid Framework

A total synthesis of the racemic modification, (±)-2, of the tazettine-type alkaloid 3-O-demethylmacronine is described. The key steps are an intramolecular Alder-ene (IMAE) reaction and a lactam-to-lactone rearrangement of tetracycle 13, a compound that embodies the haemanthidine alkaloid framework.

Therapeutic Potentials of Microalgae in the Treatment of Alzheimer's Disease

Current research is geared towards the discovery of new compounds with strong neuroprotective potential and few or no side effects compared to synthetic drugs. This review focuses on the potentials of extracts and biologically active compounds derived from microalgal biomass for the treatment and management of Alzheimer’s disease (AD). Microalgal research has gained much attention recently due to its contribution to the production of renewable fuels and the ability of alga cells to produce several secondary metabolites such as carotenoids, polyphenols, sterols, polyunsaturated fatty acids and polysaccharides. These compounds exhibit several pharmacological activities and possess neuroprotective potential. The pathogenesis of Alzheimer’s disease (AD) involves complex mechanisms that are associated with oxidative stress, cholinergic dysfunction, neuronal damage, protein misfolding and aggregation. The antioxidant, anticholinesterase activities as well as the inhibitory effects of some bioactive compounds from microalgae extracts on β-amyloid aggregation and neuronal death are discussed extensively. Phytochemical compounds from microalgae are used as pharmaceuticals, nutraceuticals and food supplements, and may possess neuroprotective potentials that are relevant to the management and/or treatment of AD.

The Biological Activity of Alkaloids from the Amaryllidaceae: From Cholinesterases Inhibition to Anticancer Activity

Modern research has shown that Amaryllidaceae alkaloids represent a rich reservoir of potential small chemical molecules exhibiting several medicinal properties through various mechanisms. Among the many Amaryllidaceae compounds, galanthamine has been given a great amount of attention due to the fact that it possesses potent acetylcholinesterase inhibitory activity. In spite of the amount of evidence indicating the potential usefulness of Amaryllidaceae alkaloids in therapy, research groups have focused their attention on the other alkaloids present in this plant family. New investigations have shed light on many aspects of the structure of Amaryllidaceae alkaloids and on their semisynthetic modification, function, and mechanisms underlying in vitro and in vivo activity. In addition, Amaryllidaceae alkaloids have frequently been identified as having promising cytotoxic properties against cancer cell lines. While follow-up studies have repeatedly shown that Amaryllidaceae alkaloids and their derivatives demonstrate antiproliferative, cytotoxic and apoptosis-inducing activity, the mechanisms remain unclear. This review addresses the most important Amaryllidaceae alkaloids with anticancer potential, particularly those that have been studied for the purpose of gaining a better understanding of the basis of the activity at the cellular and molecular level.

Synthetic Strategies for 5- and 6-Membered Ring Azaheterocycles Facilitated by Iminyl Radicals

The totality of chemical space is so immense that only a small fraction can ever be explored. Computational searching has indicated that bioactivity is associated with a comparatively small number of ring-containing structures. Pyrrole, indole, pyridine, quinoline, quinazoline and related 6-membered ring-containing aza-arenes figure prominently. This review focuses on the search for fast, efficient and environmentally friendly preparative methods for these rings with specific emphasis on iminyl radical-mediated procedures. Oxime derivatives, particularly oxime esters and oxime ethers, are attractive precursors for these radicals. Their use is described in conventional thermolytic, microwave-assisted and UV-vis based preparative procedures. Photoredox-catalyzed protocols involving designer oxime ethers are also covered. Choice can be made amongst these synthetic strategies for a wide variety of 5- and 6-membered ring heterocycles including phenanthridine and related aza-arenes. Applications to selected natural products and bioactive molecules, including trispheridine, vasconine, luotonin A and rutaecarpine, are included.

Renal toxic ingredients and their toxicology from traditional Chinese medicine

INTRODUCTION

There have been increasing concerns regarding adverse reactions and toxicity incidents caused by traditional Chinese medicines (TCMs), among which the nephrotoxicity is particularly worrying.

AREAS COVERED

This review summarizes the ingredients with renal toxicity from some TCMs through searching the relevant literature published over the past two decades. Renal toxicity components from TCMs include aristolochic acids (AAS), alkaloids, anthraquinones and others. TCM renal toxicity is most commonly caused by AAS and some alkaloids. AAS mainly come from Aristolochia contorta Bunge, Aristolochia manshuriensis Kom, Clematis Chinensis Osbeck, Aristolochia cathcartii Hook. Some renal toxic alkaloids are derived from Tripterygium regelii Sprague et Takeda, Stephania tetrandra S. Moore, Strychnos nux-vomica Linn. and Aconitum carmichaeli Debx. A few kinds of anthraquinones, flavonoids, and glycosides from TCMs also cause renal toxicity. All of these renal toxicity components and their associated renal toxicity, structures and toxic mechanism are introduced in detail in this review.

EXPERT OPINION

Given the complexity of the toxic components, a lot of work needs to be done to analyze the specific modes of action of toxic components in vivo and in vitro, in particular, to elucidate the molecular mechanism of toxicity, in order to reduce the occurrence of renal toxicity of TCM.

Amaryllidaceae and Sceletium alkaloids

The latest progress on the isolation, identification, biological activity and synthetic studies of the structurally diverse alkaloids from plants of family Amaryllidaceae has been summarized in this review.