Towards a molecular understanding of the biosynthesis of amaryllidaceae alkaloids in support of their expanding medical use

Alliums as Potential Antioxidants and Anticancer Agents

The genus Allium plants, including onions, garlic, leeks, chives, and shallots, have long been recognized for their potential health benefits, particularly in oxidative and cancer prevention. Among them, onions and garlic have been extensively studied, unveiling promising biological activities that are indicative of their potential as potent antioxidant and anticancer agents. Research has revealed a rich repository of bioactive compounds in Allium species, highlighting their antioxidative properties and diverse mechanisms that target cancer cells. Compounds such as allicin, flavonoids, and organosulfur compounds (OSCs) exhibit notable antioxidant and anticancer properties, affecting apoptosis induction, cell cycle arrest, and the inhibition of tumor proliferation. Moreover, their antioxidant and anti-inflammatory attributes enhance their potential in cancer therapy. Studies exploring other Allium species beyond onions and garlic have revealed similar biological activities, suggesting a broad spectrum of natural products that could serve as promising candidates for developing novel anticancer treatments. Understanding the multifaceted potential of Allium plants will pave the way for innovative strategies in oxidative and cancer treatment and prevention, offering new avenues for pharmaceutical research and dietary interventions. Therefore, in this review, we compile an extensive analysis of the diversity of various Allium species, emphasizing their remarkable potential as effective agents.

Recent advances in the total synthesis of galantamine, a natural medicine for Alzheimer's disease

Covering: 2006 to 2023(-)-Galantamine is a natural product with distinctive structural features and potent inhibitory activity against acetylcholine esterase (AChE). It is clinically approved for the treatment of Alzheimer's disease. The clinical significance and scarcity of this natural product have prompted extensive and ongoing efforts towards the chemical synthesis of this challenging tetracyclic structure. The objective of this review is to summarize and discuss recent progress in the total synthesis of galantamine from 2006 to 2023. The contents are organized according to the synthetic strategies for the construction of the quaternary center. Key features of each synthesis have been highlighted, followed by a summary and outlook at the end.

The Anti-Cholinesterase Potential of Fifteen Different Species of Narcissus L. (Amaryllidaceae) Collected in Spain

Narcissus L. is a renowned plant genus with a notable center of diversity and is primarily located in the Mediterranean region. These plants are widely recognized for their ornamental value, owing to the beauty of their flowers; nonetheless, they also hold pharmacological importance. In Europe, pharmaceutical companies usually use the bulbs of Narcissus pseudonarcissus cv. Carlton to extract galanthamine, which is one of the few medications approved by the FDA for the palliative treatment of mild-to-moderate symptoms of Alzheimer's disease. The purpose of this study was to evaluate the potential of these plants in Alzheimer's disease. The alkaloid extract from the leaves of different species of Narcissus was obtained by an acid-base extraction work-up -procedure. The biological potential of the samples was carried out by evaluating their ability to inhibit the enzymes acetyl- and butyrylcholinesterase (AChE and BuChE, respectively). The species N. jacetanus exhibited the best inhibition values against AChE, with IC50 values of 0.75 ± 0.03 µg·mL-1, while N. jonquilla was the most active against BuChE, with IC50 values of 11.72 ± 1.15 µg·mL-1.

Interplay between Amaryllidaceae alkaloids, the bacteriome and phytopathogens in Lycoris radiata

Alkaloids are a large group of plant secondary metabolites with various structures and activities. It is important to understand their functions in the interplay between plants and the beneficial and pathogenic microbiota. Amaryllidaceae alkaloids (AAs) are unique secondary metabolites in Amaryllidaceae plants. Here, we studied the interplay between AAs and the bacteriome in Lycoris radiata, a traditional Chinese medicinal plant containing high amounts of AAs. The relationship between AAs and bacterial composition in different tissues of L. radiata was studied. In vitro experiments revealed that AAs have varying levels of antimicrobial activity against endophytic bacteria and pathogenic fungi, indicating the importance of AA synthesis in maintaining a balance between plants and beneficial/pathogenic microbiota. Using bacterial synthetic communities with different compositions, we observed a positive feedback loop between bacteria insensitive to AAs and their ability to increase accumulation of AAs in L. radiata, especially in leaves. This may allow insensitive bacteria to outcompete sensitive ones for plant resources. Moreover, the accumulation of AAs enhanced by insensitive bacteria could benefit plants when challenged with fungal pathogens. This study highlights the functions of alkaloids in plant-microbe interactions, opening new avenues for designing plant microbiomes that could contribute to sustainable agriculture.

Anti-SARS-CoV-2 Activity and Cytotoxicity of Amaryllidaceae Alkaloids from Hymenocallis littoralis

The Amaryllidaceae species are well-known as a rich source of bioactive compounds in nature. Although Hymenocallis littoralis has been studied for decades, its polar components were rarely explored. The current phytochemical investigation of Amaryllidaceae alkaloids from H. littoralis led to the identification of three previously undescribed compounds: O-demethyl-norlycoramine (1), (−)-2-epi-pseudolycorine (2) and (+)-2-epi-pseudolycorine (3), together with eight known compounds: 6α-hydroxyhippeastidine (4), 6β-hydroxyhippeastidine (5), lycorine (6), 2-epi-lycorine (7), zephyranthine (8), ungeremine (9), pancratistatin (10) and 9-O-demethyl-7-O-methyllycorenine (11). Among the eight previously reported compounds, five were isolated from H. littoralis for the first time (compounds 4, 5, 7, 8, and 9). Compounds 1, 4, 5, 7, 8, and 11 exhibited weak anti-SARS-CoV-2 activity (EC50 = 40–77 µM) at non-cytotoxic concentrations. Assessment of cytotoxicity on the Vero-E6 cell line revealed lycorine and pancratistatin as cytotoxic substances with CC50 values of 1.2 µM and 0.13 µM, respectively. The preliminary structure-activity relationship for the lycorine-type alkaloids in this study was further investigated, and as a result ring C appears to play a crucial role in their anti-SARS-CoV-2 activity.

The Phytochemistry and Pharmacology of Tulbaghia, Allium, Crinum and Cyrtanthus: ‘Talented’ Taxa from the Amaryllidaceae

Amaryllidaceae is a significant source of bioactive phytochemicals with a strong propensity to develop new drugs. The genera Allium, Tulbaghia, Cyrtanthus and Crinum biosynthesize novel alkaloids and other phytochemicals with traditional and pharmacological uses. Amaryllidaceae biomolecules exhibit multiple pharmacological activities such as antioxidant, antimicrobial, and immunomodulatory effects. Traditionally, natural products from Amaryllidaceae are utilized to treat non-communicable and infectious human diseases. Galanthamine, a drug from this family, is clinically relevant in treating the neurocognitive disorder, Alzheimer’s disease, which underscores the importance of the Amaryllidaceae alkaloids. Although Amaryllidaceae provide a plethora of biologically active compounds, there is tardiness in their development into clinically pliable medicines. Other genera, including Cyrtanthus and Tulbaghia, have received little attention as potential sources of promising drug candidates. Given the reciprocal relationship of the increasing burden of human diseases and limited availability of medicinal therapies, more rapid drug discovery and development are desirable. To expedite clinically relevant drug development, we present here evidence on bioactive compounds from the genera Allium, Tulgbaghia, Cyrtanthus and Crinum and describe their traditional and pharmacological applications.

Biotechnological Approaches to Optimize the Production of Amaryllidaceae Alkaloids

Amaryllidaceae alkaloids (AAs) are plant specialized metabolites with therapeutic properties exclusively produced by the Amaryllidaceae plant family. The two most studied representatives of the family are galanthamine, an acetylcholinesterase inhibitor used as a treatment of Alzheimer's disease, and lycorine, displaying potent in vitro and in vivo cytotoxic and antiviral properties. Unfortunately, the variable level of AAs' production in planta restricts most of the pharmaceutical applications. Several biotechnological alternatives, such as in vitro culture or synthetic biology, are being developed to enhance the production and fulfil the increasing demand for these AAs plant-derived drugs. In this review, current biotechnological approaches to produce different types of bioactive AAs are discussed.

Chemical analysis of essential oil component, perfume and synthetic essential oil of narcissus and its harmful compounds

Within this work, tazetta, one of the fragrant narcissus species used in the perfume industry, was extracted by steam distillation. The extracts were chemically analyzed by gas chromatography coupled with a mass spectrometer (GC/MS). All substances of perfume, synthetic essence, and essential oil of narcissus flower were prepared and their constituents were identified and compared based on GC/MS results. Their harmful compounds were also identified using MSDS and LD50 methods. According to the obtained information of MSDS and LD50, essential oil of flower, perfume and synthetic essence all contain harmful compounds with many side effects to be considered with extra care for the human health.

Amaryllidaceae plants: a potential natural resource for the treatment of Chagas disease

Background

Chagas disease is a neglected zoonosis caused by the parasite Trypanosoma cruzi. It affects over six million people, mostly in Latin America. Drugs available to treat T. cruzi infection have associated toxicity and questionable efficacy at the chronic stage. Hence, the discovery of more effective and safer drugs is an unmet medical need. For this, natural products represent a pool of unique chemical diversity that can serve as excellent templates for the synthesis of active molecules.

Methods

A collection of 79 extracts of Amaryllidaceae plants were screened against T. cruzi. Active extracts against the parasite were progressed through two cell toxicity assays based on Vero and HepG2 cells to determine their selectivity profile and discard those toxic to host cells. Anti-T. cruzi-specific extracts were further qualified by an anti-amastigote stage assay.

Results

Two extracts, respectively from Crinum erubescens and Rhodophiala andicola, were identified as highly active and specific against T. cruzi and its mammalian replicative form.

Conclusions

The results retrieved in this study encourage further exploration of the chemical content of these extracts in search of new anti-T. cruzi drug development starting points.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04837-9.

Galantamine Quantity and Alkaloid Profile in the Bulbs of Narcissus tazetta and daffodil cultivars (Amaryllidaceae) Grown in Israel

Alkaloids produced by the bulbs of the Amaryllidaceae are a source of pharmaceutical compounds. The main alkaloid, galantamine, is a reversible acetylcholinesterase inhibitor and allosteric nicotinic receptor modulator, which slows cognitive and functional decline in mild to moderate dementia due to Alzheimer’s disease. Having a complex stereochemistry, the organic synthesis of galantamine for pharmaceutical uses is highly challenging and not always economically viable, and it is therefore isolated from Amaryllidaceae bulbs. In the present study, galantamine was extracted and quantified in Narcissus bulbs from five cultivars (cvs.), Fortune, Carlton, Ice Follies, Galilee and Ziva, which were grown in Israel under various conditions. Results show that the cvs. Fortune, Carlton and Ice Follies bulbs contained 285 ± 47, 452 ± 73 and 69 ± 17 µg g⁻¹ galantamine, respectively, while the Galilee and Ziva bulbs contained relatively low concentrations of galantamine (1–20 µg g⁻¹). Irrigation levels and pruning conditions did not affect the galantamine contents. Additionally, the alkaloids profile of the five cvs. was analyzed and characterized using LC-MS/MS showing that galantamine-type alkaloids were mainly detected in the Fortune and Carlton bulbs, lycorine-type alkaloids were mainly detected at the Galilee and Ziva bulbs and vittatine-type alkaloids were mainly detected in the Ice Follies bulbs. The present research is the first to characterize the alkaloids profile in the Narcissus bulbs of Galilee and Ziva, indigenous cvs. grown in Israel. The antiviral and anticancer alkaloids lycorine and lycorinine were the main alkaloids detected in the bulbs of those cultivars.

The snowdrop, wellspring of galanthamine : A brief descriptive and scientific history

A history of the common snowdrop, Galanthus nivalis, is set out in folkloric fashion. Its religious connection is evident as well as the inspiration it arouses in artists and in ordinary persons. It is intended to shed light on the initial works relating to the snowdrop's alkaloid, galanthamine, performed by Soviet and Bulgarian scientists, which lie buried away and generally remain unknown. A brief history and nature of alkaloids continues with the emphasis placed on galanthamine. Heretofore hidden uses of snowdrops in traditional (folk) medicine are unveiled. An anticholinesterase with central and peripheral activity, feasible clinical indications with galanthamine are described. Certain disorders for which galanthamine has been deemed beneficial are presented for their historical value. Ongoing research regarding drugs and chemicals developed from the snowdrop and galanthamine is mentioned.

Relative expression of putative genes involved in galanthamine and other Amaryllidaceae alkaloids biosynthesis in Narcissus field and in vitro tissues

The Narcissus pseudonarcissus cv. Carlton contains Amaryllidaceae alkaloids namely galanthamine, lycorine, homolycorine, narciclasine, which are noted for their pharmaceutical properties such as for the treatment of early to mid-stage Alzheimer's diseases, cancer, tumor etc. Alkaloid biosynthesis using plant in vitro systems has been considered as a tool for drug discovery and the pathways are starting to be understood but still far from complete. Therefore, the study was emphasized to observe the relative expressions of putative genes involved in the biosynthetic pathway leading to the Amaryllidaceae alkaloids in field grown bulbs and developing cell culture systems in Narcissus. MS media fortified with growth regulators were used for the development of tissue culture from Carlton twin-scale explants. MS medium with high auxin, 20 mg/l NAA was the best medium for callus growth and maintenance while media with low auxin, 4 mg/l NAA and MS basal media gave the maximum bulblets. Field tissues showed a higher amount of galanthamine content; i.e. basal plate (1050-1310 µg Gal/g FW) and bulb (980-1150 µg Gal/g FW) than the culture derived samples; callus (1.0-7.0 µg Gal/g FW) and bulblets (12-215 µg Gal/g FW) on a fresh weight (FW) basis. GC-MS chromatograms of samples under study also showed the presence of other important alkaloids i.e. lycorine, homolycorine, lycorenine, haemanthamine, crinamine, lycoramine and tazettine. RNA extracted from in vitro callus, bulblets and field grown bulb, basal plate were used for PCR to detect the relative expression of putative genes; P450, PAL, TYDC and NpO₄OMT normalized to actin. The selected transcripts for P450s and TYDC were expressed in both field and in vitro tissues. Higher expressions of PAL were observed in calli than field samples. The expression of NpN4OMT was notably higher in field samples than in vitro tissues. Therefore, in vitro tissues could be a good source for the reproducible and easy extraction of alkaloids from plants.

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.

Recent Progress in Amaryllidaceae Biotechnology

Plants belonging to the monocotyledonous Amaryllidaceae family include about 1100 species divided among 75 genera. They are well known as medicinal and ornamental plants, producing pharmaceutically important alkaloids, the most intensively investigated of which are galanthamine and lycorine. Amaryllidaceae alkaloids possess various biological activities, the most important one being their anti-acetylcholinesterase activity, used for the treatment of Alzheimer's disease. Due to increased demand for Amaryllidaceae alkaloids (mainly galanthamine) and the limited availability of plant sources, in vitro culture technology has attracted the attention of researchers as a prospective alternative for their sustainable production. Plant in vitro systems have been extensively used for continuous, sustainable, and economically viable production of bioactive plant secondary metabolites. Over the past two decades, a significant success has been demonstrated in the development of in vitro systems synthesizing Amaryllidaceae alkaloids. The present review discusses the state of the art of in vitro Amaryllidaceae alkaloids production, summarizing recently documented plant in vitro systems producing them, as well as the authors' point of view on the development of biotechnological production processes with a focus on the future prospects of in vitro culture technology for the commercial production of these valuable alkaloids.

Bacterial endophytes from Lycoris radiata promote the accumulation of Amaryllidaceae alkaloids

Lycoris radiata is the major source of Amaryllidaceae alkaloids, having various medicinal activities. However, the low content of these alkaloids in planta limits their pharmaceutical development and utilization. In this study, the ability of bacterial endophytes to enhance the accumulation of five important Amaryllidaceae alkaloids was investigated. A total of 188 bacterial endophytes were isolated from L. radiata and their composition and diversity were analyzed. Fourteen ones were demonstrated to significantly increase the concentration of the alkaloids of interest in different organs, up to 11.1-fold over the control level, with no adverse influence on the plant growth. An additional 3 bacterial endophytes were found to significantly increase the dry weight of L. radiata with no adverse influence on the concentration of the alkaloids in planta, so the total yield of alkaloids in planta was increased up to 2.4-fold over the control level. Considering the plant growth-promoting abilities of these bacterial endophytes, it is speculated that the indole-3-acetic acid and siderophore secreted by them, combined with their nitrogen fixation ability, may contribute to the enhanced plant growth and the increased alkaloid accumulation in L. radiata. To our knowledge, this work is firstly defining the diversity of culturable bacterial endophytes in L. radiata and determining which species promoted the accumulation of Amaryllidaceae alkaloids. It provides several valuable bacterial inoculants that can be further applied to improve alkaloid production in L. radiata and broadens our understanding of the interactions between a medicinal plant and the bacterial endophytes.

Macrophylloflavone: A New Biflavonoid from Garcinia macrophylla Mart. (Clusiaceae) for Antibacterial, Antioxidant, and Anti-Type 2 Diabetes Mellitus Activities

Investigations of antibacterial, antioxidant, and anti-type 2 diabetes mellitus activities have been carried out on Garcinia macrophylla Mart. plant extract fractions. An isolate from a fraction of ethyl acetate extract was characterized with spectroscopic data. A new biflavonoid compound was found to have a skeleton of 5,7,4′,5″,7″,3‴,4‴-heptahydroxyflavanone[3-6″] flavones which was named macrophylloflavone (1). The compound was evaluated for its antibacterial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 with cephazolin as a positive control, antioxidant assay against 2,2 diphenyl-1-picrylhydrazyl (DPPH) with ascorbic acid as the positive control, and anti-type 2 diabetes mellitus treatment with metformin as a positive control. The biflavonoid compound exhibited a good inhibition for bacteria and free radical DPPH. Furthermore, biflavonoid compound treatment on the diabetic rats suggested its ability to decrease the blood glucose level. This study provided evidence that the plant has antibacterial, antioxidant, and antidiabetic properties.

Application of in vivo solid phase microextraction (SPME) in capturing metabolome of apple (Malus ×domestica Borkh.) fruit

An in vivo direct-immersion SPME sampling coupled to comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GCxGC-ToFMS) was employed to capture real-time changes in the metabolome of ‘Honeycrisp’ apples during ripening on the tree. This novel sampling approach was successful in acquiring a broad metabolic fingerprint, capturing unique metabolites and detecting changes in metabolic profiles associated with fruit maturation. Several metabolites and chemical classes, including volatile esters, phenylpropanoid metabolites, 1-octen-3-ol, hexanal, and (2E,4E)-2,4-hexadienal were found to be up-regulated in response to fruit maturation. For the first time, Amaryllidaceae alkaloids, metabolites with important biological activities, including anti-cancer, anti-viral, anti-parasitic, and acetylcholinesterase (AChE) inhibitory activity, were detected in apples. Considering the elimination of oxidative degradation mechanisms that adversely impact the representativeness of metabolome obtained ex vivo, and further evidence that lipoxygenase (LOX) pathway contributes to volatile production in intact fruit, in vivo DI-SPME represents an attractive approach for global plant metabolite studies.

Fungal endophytes promote the accumulation of Amaryllidaceae alkaloids in Lycoris radiata

Lycoris radiata is a main source of Amaryllidaceae alkaloids; however, the low content of these alkaloids in planta remains a limit to their pharmaceutical development and utilization. The accumulation of secondary metabolites can be enhanced in plants inoculated with fungal endophytes. In this study, we analysed the diversity of culturable fungal endophytes in different organs of L. radiata. Then, by analysing the correlation between the detectable rate of each fungal species and the content of each tested alkaloid, we proposed several fungal candidates implicated in the increase of alkaloid accumulation. This was verified by inoculating these candidates to L. radiata plants. Based on the results of two independent experiments conducted in May 2018 and October 2019, the individual inoculation of nine fungal endophytes significantly increased the total content of the tested alkaloids in the entire L. radiata plants. This is the first study in L. radiata to show that fungal endophytes are able to improve the accumulation of various alkaloids. Therefore, our results provide insights into a better understanding of interactions between plants and fungal endophytes and suggest an effective strategy for enhancing the alkaloid content in the cultivation of L. radiata.

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.

Transcriptome Analysis of Different Tissues Reveals Key Genes Associated With Galanthamine Biosynthesis in Lycoris longituba

L ycoris longituba is a traditional medicinal plant containing the bioactive compound galanthamine (Gal), a type of Amaryllidaceae alkaloid and can be used to treat Alzheimer's disease. However, research on its genome or transcriptome and associated genes in the biosynthetic pathway is incomplete. In this study, we estimated the nuclear genome size of this species to be 29.33 Gb by flow cytometry. Then, RNA sequencing of the leaves, roots, and bulbs of L. longituba was carried out. After de novo assembly, 474,589 all-transcripts and 333,440 all-unigenes were finally generated. In addition, the differentially expressed genes (DEGs) were identified, and genes involved in the galanthamine metabolic pathway encoding tyrosine decarboxylase (TYDC), phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), p-coumarate 3-hydroxylase (C3H), norbelladine synthase (NBS), norbelladine 4'-O-methyltransferase (OMT), and noroxomaritidine synthase (CYP96T1) were detected and validated by real-time quantitative PCR analysis. One candidate gene, Lycoris longituba O-Methyltransferase (LlOMT), was identified in the proposed galanthamine biosynthetic pathway. Sequence analysis showed that LlOMT is a class I OMT. LlOMT is localized in the cytoplasm, and biochemical analysis indicated that the recombinant LlOMT catalyzes norbelladine to generate 4'-O-methylnorbelladine. The protoplast transformation result showed that the overexpression of LlOMT could increase the Gal content. Our results indicate that LlOMT may play a role in galanthamine biosynthesis in L. longituba. This work provides a useful resource for the metabolic engineering of Amaryllidaceae alkaloids.

The Genus Nerine Herb. (Amaryllidaceae): Ethnobotany, Phytochemistry, and Biological Activity

Nerine Herbert, family Amaryllidaceae, is a genus of about 30 species that are native to South Africa, Botswana, Lesotho, Namibia, and Swatini (formerly known as Swaziland). Species of Nerine are autumn-flowering, perennial, bulbous plants, which inhabit areas with summer rainfall and cool, dry winters. Most Nerine species have been cultivated for their elegant flowers, presenting a source of innumerable horticultural hybrids. For many years, species of Nerine have been subjected to extensive phytochemical and pharmacological investigations, which resulted in either the isolation or identification of more than fifty Amaryllidaceae alkaloids belonging to different structural types. Amaryllidaceae alkaloids are frequently studied for their interesting biological properties, including antiviral, antibacterial, antitumor, antifungal, antimalarial, analgesic, cytotoxic, and cholinesterase inhibition activities. The present review aims to summarize comprehensively the research that has been reported on the phytochemistry and pharmacology of the genus Nerine.

Exploration of Floral Volatile Organic Compounds in Six Typical Lycoris taxa by GC-MS

Lycoris, which is known as the ‘Chinese tulip,’ has diverse flower colors and shapes, and some species have a delicate fragrance. However, limited studies have reported the volatile organic compounds (VOCs) of Lycoris. In this study, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was used to analyze the floral VOCs of six typical Lycoris taxa. Thirty-two VOCs were identified, including terpenoids, alcohols, esters, aldehydes, ketones, and phenols. The aldehyde and terpenoid contents in Lycoris aurea were higher than in the other taxa, and the ester and alcohol contents in L. sprengeri were the highest compared to all taxa tested. Compared with other species and cultivars, L. longituba and L. longituba var. flava were the two most scented taxa and the VOCs were dominated by terpenoids and esters. L. radiate and L. chinensis were two unscented taxa and, accordingly, the VOC content was weak. A partial least squares discriminate analysis of the floral VOCs among the six Lycoris taxa showed that the six taxa could be successfully separated. Moreover, the VOCs of L. longituba and L. longituba var. flava clustered together. β-Ocimene was verified as the most important aroma compound, as determined via the calculation of the variable importance in projection values and significance analysis. β-Ocimene and its trans isomer, trans-β-ocimene, had a high relative content in L. longituba, L. longituba var. flava, L. aurea, and L. chinensis but were not detected in L. sprengeri and L. radiata. These results indicate that floral VOCs might be selected during the evolutional processes of Lycoris, and β-ocimene could be the most typical VOC among the different Lycoris taxa.

The versatile O-methyltransferase LrOMT catalyzes multiple O-methylation reactions in amaryllidaceae alkaloids biosynthesis

Amaryllidaceae alkaloids are unique benzylphenethylamine derivatives that comprise of more than 600 members with a huge chemical diversity. Most of them showed interesting bioactivities, for instance, galanthamine (GAL) is clinically used for Alzheimer's disease treatment. All Amaryllidaceae alkaloids had been thought to be derived from 4'-O-methylnorbelladine originated from norbelladine catalyzed by norbelladine 4'-O-methyltransferase (N4OMT). Herein we mined the transcriptome datasets of Lycoris radiata, a GAL-producing plant. LrOMT was cloned, overexpressed in Escherichia coli, and purified to homogeneity. Bioinformatics analysis and enzymatic activity assays revealed that LrOMT is an S-adenosylmethionine-dependent Class I OMT. LrOMT exhibited both para- and meta-O-methylation activities toward norbelladine to give 4'- and 3'-O-methylnorbelladine. Twenty-four analogues, including the proposed biosynthetic intermediates, were introduced to investigate the substrate scope of LrOMT and it showed that the aromatic substrates should have two vicinal hydroxyl groups. The LrOMT-catalyzed O-methylation preference is dependent on the properties of the binding group of the substrates. The transcription levels of LrOMT were positively associated with the accumulation of the Amaryllidaceae alkaloids and the biosynthetic intermediates in L. radiata. The present work revealed that LrOMT catalyzes multiple O-methylation reactions and its characterization will be helpful to uncover novel biosynthetic genes for Amaryllidaceae alkaloids biosynthesis.

Developmental Regulation of the Expression of Amaryllidaceae Alkaloid Biosynthetic Genes in Narcissus papyraceus

Amaryllidaceae alkaloids (AAs) have multiple biological effects, which are of interest to the pharmaceutical industry. To unleash the potential of Amaryllidaceae plants as pharmaceutical crops and as sources of AAs, a thorough understanding of the AA biosynthetic pathway is needed. However, only few enzymes in the pathway are known. Here, we report the transcriptome of AA-producing paperwhites (Narcissus papyraceus Ker Gawl). We present a list of 21 genes putatively encoding enzymes involved in AA biosynthesis. Next, a cDNA library was created from 24 different samples of different parts at various developmental stages of N. papyraceus. The expression of AA biosynthetic genes was analyzed in each sample using RT-qPCR. In addition, the alkaloid content of each sample was analyzed by HPLC. Leaves and flowers were found to have the highest abundance of heterocyclic compounds, whereas the bulb, the lowest. Lycorine was also the predominant AA. The gene expression results were compared with the heterocyclic compound profiles for each sample. In some samples, a positive correlation was observed between the gene expression levels and the amount of compounds accumulated. However, due to a probable transport of enzymes and alkaloids in the plant, a negative correlation was also observed, particularly at stage 2.

Amaryllidaceae alkaloids: identification and partial characterization of montanine production in Rhodophiala bifida plant

Rhodophiala bifida (R. bifida) is a representative of the Amaryllidaceae plant family and is rich in montanine, an alkaloid with high pharmaceutical potential. Despite the interest in these compounds, many steps of the biosynthetic pathway have not been elucidated. In this study, we identified the alkaloids produced in different organs of R. bifida under different growth conditions, set up the conditions for in vitro R. bifida regeneration and initiated the molecular characterization of two R. bifida genes involved in alkaloids biosynthesis: the Norbelladine 4'-O-Methyltransferase (RbN4OMT) and the Cytochrome P450 (RbCYP96T). We show that montanine is the main alkaloid produced in the different R. bifida organs and developed a direct organogenesis regeneration protocol, using twin-scale explants cultivated on media enriched with naphthalene acetic acid and benzyladenine. Finally, we analyzed the RbN4OMT and RbCYP96T gene expressions in different organs and culture conditions and compared them to alkaloid production. In different organs of R. bifida young, adult and regenerated plants, as well as under various growing conditions, the transcripts accumulation was correlated with the production of alkaloids. This work provides new tools to improve the production of this important pharmaceutical compound and for future biotechnological studies.

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.

Development of 17 novel microsatellite markers for Lycoris aurea and L. radiata (Amaryllidaceae) using next-generation sequencing

PREMISE OF THE STUDY

Lycoris is an ornamental and medicinal plant. We developed microsatellite markers for L. aurea and L. radiata simultaneously by using a hybrid between these two species.

METHODS AND RESULTS

Ion Torrent next-generation sequencing produced 1,784,504 reads. Testing 64 primer sets allowed for the development of 17 novel microsatellite markers: 16 for L. aurea, 10 for L. radiata, and nine common markers. Lycoris aurea had one to 12 alleles per locus and observed and expected heterozygosity levels of 0-0.923 and 0.038-0.809, respectively. Lycoris radiata had three to 12 alleles per locus and observed and expected heterozygosity levels of 0-0.909 and 0.127-0.797, respectively. Ten markers were cross-amplified for L. sprengeri.

CONCLUSIONS

Hybrid sequencing can facilitate the cost-effective development of molecular markers for parental species. The markers developed here are useful for studying Lycoris population structure.

Sources for developing new medicinal products: biochemical investigations on alcoholic extracts obtained from aerial parts of some Romanian Amaryllidaceae species

BACKGROUND

Although Galanthus nivalis L. (snowdrop) is known for the galanthamine content, used in the treatment of Alzheimer disease, the polyphenolic compounds of Amaryllidaceae species are less studied. Proper understanding of the polyphenolics in these extracts and of their antioxidant and antimicrobial properties may allow a reconsideration of their medicinal uses.

METHODS

The polyphenolic content of four selected Amaryllidaceae species harvested from Romania (Galanthus nivalis L., Narcissus pseudonarcissus L., N. poeticus L. and Leucojum vernum L.) was determined by spectrophotometric methods; the identification of phenolic compounds was performed by a HPLC-MS method, in order to establish their polyphenolic fingerprints. For the evaluation of the antioxidant potential the following methods were employed: DPPH radical scavenging, FRAP, hemoglobin ascorbate peroxidase activity inhibition (HAPX), inhibition of lipid peroxidation catalyzed by cytochrome c, and electron paramagnetic resonance (EPR) spectroscopy assays. Antimicrobial activity was assessed using the disc diffusion method.

RESULTS

Qualitative and quantitative analyses highlight important amount of polyphenols (over 15 mg/g); the main identified compounds are chlorogenic and p-coumaric acids in all species. Only G. nivalis shows antioxidant activity by all the used methods. G. nivalis and L. vernum strongly inhibits the growth of S. aureus, while N. poeticus shows a very good antifungal activity.

CONCLUSIONS

The results of this study provide a new approach to the properties and therapeutic uses of some Romanian widespread Amaryllidaceae species that could be considered sources of developing new medicinal products with anti anti-staphylococcal and antifungal activity.

Diversity-Oriented Approach Toward the Syntheses of Amaryllidaceae Alkaloids via a Common Chiral Synthon

Functionalized hydroindole (1), a common chiral synthon, for versatile transformations to synthesize a broad range of Amaryllidaceae alkaloids (AAs) including (-)-crinine, (-)-crinane, (-)-amabiline, (+)-mesembrine, (-)-maritidine, (-)-oxomaritidine, and (+)-mesembrane is reported. Scaffold 1 is found as a prime structural motif in a wide variety of the AAs and is a novel synthon toward designing a divergent route for the synthesis of these natural products. This is established in a few steps, starting from a chiral aza-bicyclo-heptene sulfone scaffold (2) via conjugate addition and concomitant stereoselective ring opening with allylmagnesium bromide, a key step that generates a crucial quaternary stereocenter, fixing the stereochemistry of the rest of the molecule at an early stage. One carbon truncation followed by intramolecular reductive amination led to the desired core 1 in a multigram scale.

Molecular Cloning and Characterization of a meta/para-O-Methyltransferase from Lycoris aurea

O-methyltransferases (OMTs) have been demonstrated to play key roles in the biosynthesis of plant secondary metabolites, such as alkaloids, isoprenoids, and phenolic compounds. Here, we isolated and characterized an OMT gene from Lycoris aurea (namely LaOMT1), based on our previous transcriptome sequencing data. Sequence alignment and phylogenetic analysis showed that LaOMT1 belongs to the class I OMT, and shares high identity to other known plant OMTs. Also, LaOMT1 is highly identical in its amino acid sequence to NpN4OMT, a norbelladine 4′-OMT from Narcissus sp. aff. pseudonarcissus involved in the biosynthesis of Amaryllidaceae alkaloids. Biochemical analysis indicated that the recombinant LaOMT1 displayed both para and metaO-methylation activities with caffeic acid and 3,4-dihydroxybenzaldehyde, and showed a strong preference for the meta position. Besides, LaOMT1 also catalyzes the O-methylation of norbelladine to form 4′-O-methylnorbelladine, which has been demonstrated to be a universal precursor of all the primary Amaryllidaceae alkaloid skeletons. The results from quantitative real-time PCR assay indicated that LaOMT1 was ubiquitously expressed in different tissues of L. aurea, and its highest expression level was observed in the ovary. Meanwhile, the largest concentration of lycorine and galanthamine were found in the ovary, whereas the highest level of narciclasine was observed in the bulb. In addition, sodium chloride (NaCl), cold, polyethylene glycol (PEG), sodium nitroprusside (SNP), and methyl jasmonate (MeJA) treatments could significantly increase LaOMT1 transcripts, while abscisic acid (ABA) treatment dramatically decreased the expression level of LaOMT1. Subcellular localization showed that LaOMT1 is mainly localized in cytoplasm and endosome. Our results in this study indicate that LaOMT1 may play a multifunctional role, and lay the foundation for Amaryllidaceae alkaloid biosynthesis in L. aurea.

Tyrosine biosynthesis, metabolism, and catabolism in plants

L-Tyrosine (Tyr) is an aromatic amino acid (AAA) required for protein synthesis in all organisms, but synthesized de novo only in plants and microorganisms. In plants, Tyr also serves as a precursor of numerous specialized metabolites that have diverse physiological roles as electron carriers, antioxidants, attractants, and defense compounds. Some of these Tyr-derived plant natural products are also used in human medicine and nutrition (e.g. morphine and vitamin E). While the Tyr biosynthesis and catabolic pathways have been extensively studied in microbes and animals, respectively, those of plants have received much less attention until recently. Accumulating evidence suggest that the Tyr biosynthetic pathways differ between microbes and plants and even within the plant kingdom, likely to support the production of lineage-specific plant specialized metabolites derived from Tyr. The interspecies variations of plant Tyr pathway enzymes can now be used to enhance the production of Tyr and Tyr-derived compounds in plants and other synthetic biology platforms.

A Review on Recent Syntheses of Amaryllidaceae Alkaloids and Isocarbostyrils (Time period mid-2016 to 2017)

Alkaloids from the Amaryllidaceae have become valuable targets for synthetic organic chemists, mainly due to their wide variety of bioactivities and potential for utilization in medicinal chemistry ventures. In addition, the structural complexity of a number of these alkaloids has also been a reason for the interest in these compounds. In this review, the last 18 months of literature was perused and synthetic highlights have been presented here, with the hope to further focus attention on this interesting class of compounds and to encourage others to synthesize these compounds and their derivatives and/or analogues. The review contains examples of syntheses from most of the important alkaloid scaffold classes previously isolated from the Amaryllidaceae, namely: lycorine, crinine, galanthamine, tazettine, montanine, phenanthridone, phenanthridine, plicamine, mesembrine and some minor scaffolds (like gracilamine).

Transcriptome and metabolome profiling of Narcissus pseudonarcissus 'King Alfred' reveal components of Amaryllidaceae alkaloid metabolism

Amaryllidaceae alkaloids (AAs) represent a diverse class of plant specialized metabolites and many display potent pharmacological activities. The AA metabolic pathway is poorly understood and resources are minimal. To enable AA pathway elucidation and novel biosynthetic enzymes discovery, we generated comprehensive metabolomic and corresponding transcriptomic datasets from different tissues of Narcissus pseudonarcissus ‘King Alfred’. In this study, we performed untargeted UPLC-QTOF-MS metabolite analysis from different tissues, which generated exhaustive list of compounds, including several AAs, most predominant and diverse in bulbs. RNA sequencing of N. pseudonarcissus ‘King Alfred’ bulbs yielded 195,347 transcripts, after assembly. Top expressed genes belong to process like metabolism, survival, and defense including alkaloid biosynthetic genes. The transcriptome contained complete sequences for all proposed genes encoding AA-biosynthetic enzymes such as tyrosine decarboxylase (TYDC1 and TYDC2), phenylalanine ammonia-lyase (PAL1 and PAL2) and phenolic acids hydroxylases (C4H and C3H) to name a few. Furthermore, transcriptome data were validated using RT-qPCR analysis and expression study in different tissues of N. pseudonarcissus ‘King Alfred’ was performed. Here, we present the first comprehensive metabolome and transcriptome study from N. pseudonarcissus ‘King Alfred’ providing invaluable resources for metabolic engineering and biotechnological applications.

Alkaloid Constituents of the Amaryllidaceae Plant Amaryllis belladonna L

The plant family Amaryllidaceae is well-known for its unique alkaloid constituents, which exhibit a wide range of biological activities. Its representative, Amaryllis belladonna, has a geographical distribution covering mainly southern Africa, where it has significant usage in the traditional medicine of the native people. In this study, A. belladonna samples collected in Brazil were examined for alkaloid content. Alkaloid profiles of A. belladonna bulbs were generated by a combination of chromatographic, spectroscopic and spectrometric methods, including GC–MS and 2D NMR. In vitro screening against four different parasitic protozoa (Trypanosoma cruzi, T. brucei rhodesiense, Leishmania donovani and Plasmodium falciparum) was carried out using the A. belladonna crude methanol extract, as well as three of its alkaloid isolates. Twenty-six different Amaryllidaceae alkaloids were identified in the A. belladonna bulb samples, and three of them were isolated. Evidence for their respective biosynthetic pathways was afforded via their mass-spectral fragmentation data. Improved data for 1-O-acetylcaranine was provided by 2D NMR experiments, together with new ¹H-NMR data for buphanamine. The crude extract and 3-O-acetylhamayne exhibited good antiprotozoal activity in vitro, although both with a high cytotoxic index.

Antiproliferative activities of Amaryllidaceae alkaloids from Lycoris radiata targeting DNA topoisomerase I

Crude Amaryllidaceae alkaloids (AAs) extracted from Lycoris radiata are reported to exhibit significant anti-cancer activity. However, the specific alkaloids responsible for the pharmacodynamic activity and their targets still remain elusive. In this context, we strived to combine affinity ultrafiltration with topoisomerase I (Top I) as a target enzyme aiming to fish out specific bioactive AAs from Lycoris radiata. 11 AAs from Lycoris radiata were thus screened out, among which hippeastrine (peak 5) with the highest Enrichment factor (EF) against Top I exhibited good dose-dependent inhibition with IC₅₀ at 7.25 ± 0.20 μg/mL comparable to camptothecin (positive control) at 6.72 ± 0.23 μg/mL. The molecular docking simulation further indicated the inhibitory mechanism between Top I and hippeastrine. The in vitro antiproliferation assays finally revealed that hippeastrine strongly inhibited the proliferation of HT-29 and Hep G2 cells in an intuitive dose-dependent manner with the IC₅₀ values at 3.98 ± 0.29 μg/mL and 11.85 ± 0.20 μg/mL, respectively, and also induced significant cellular morphological changes, which further validated our screening method and the potent antineoplastic effects. Collectively, these results suggested that hippeastrine could be a very promising anticancer candidate for the therapy of cancer in the near future.

Identification and differential regulation of microRNAs in response to methyl jasmonate treatment in Lycoris aurea by deep sequencing

Background

Lycoris aurea is a medicine-valuable and ornamental herb widely distributed in China. Former studied have showed that methyl jasmonate (MJ) treatment could increase the content of glanthamine-a worldwide medicine for symptomatic treatment of Alzheimer’s disease in genus Lycoris plants. To explore the possible role of miRNAs in the regulation of jasmonic acid signaling pathway and uncover their potential correlations, we investigated the expression profiles of small RNAs (sRNAs) and their targets in Lycoris aurea, with MJ treatment by using next-generation deep sequencing.

Results

A total of 365 miRNAs were identified, comprising 342 known miRNAs (representing 60 miRNA families) and 23 novel miRNAs. Among them, 143 known and 11 novel miRNAs were expressed differently under MJ treatment. Quantitative real-time PCR of eight selected miRNAs validated the expression pattern of these loci in response to MJ treatment. In addition, degradome sequencing analysis showed that 32 target genes were validated to be targeted by the 49 miRNAs, respectively. Gene function and pathway analyses showed that these targets such as auxin response factors (ARFs), squamosa promoter-binding like (SPL) proteins, basic helix-loop-helix (bHLH) proteins, and ubiquitin-conjugating enzyme E2 are involved in different plant processes, indicating miRNAs mediated regulation might play important roles in L. aurea response to MJ treatment. Furthermore, several L. aurea miRNAs associated with their target genes that might be involved in Amaryllidaceae alkloids biosynthehsis were also analyzed.

Conclusions

A number of miRNAs with diverse expression patterns, and complex relationships between expression of miRNAs and targets were identified. This study represents the first transcriptome-based analysis of miRNAs in Lycoris and will contribute to understanding the potential roles of miRNAs involved in regulation of MJ response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2645-y) contains supplementary material, which is available to authorized users.

The Amaryllidaceae alkaloids: biosynthesis and methods for enzyme discovery

Amaryllidaceae alkaloids are an example of the vast diversity of secondary metabolites with great therapeutic promise. The identification of novel compounds in this group with over 300 known structures continues to be an area of active study. The recent identification of norbelladine 4'-O-methyltransferase (N4OMT), an Amaryllidaceae alkaloid biosynthetic enzyme, and the assembly of transcriptomes for Narcissus sp. aff. pseudonarcissus and Lycoris aurea highlight the potential for discovery of Amaryllidaceae alkaloid biosynthetic genes with new technologies. Recent technical advances of interest include those in enzymology, next generation sequencing, genetic modification, nuclear magnetic resonance spectroscopy (NMR), and mass spectrometry (MS).

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.

Solvolysis, Electrochemistry, and Development of Synthetic Building Blocks from Sawdust

Either aldehyde or cinnamyl ether products can be selectively extracted from raw sawdust by controlling the temperature and pressure of a solvolysis reaction. These materials have been used as platform chemicals for the synthesis of 15 different synthetic substrates. The conversion of the initial sawdust-derived materials into electron-rich aryl substrates often requires the use of oxidation and reduction chemistry, and the role electrochemistry can play as a sustainable method for these transformations has been defined.