Polyamine alkaloids

Polyamine-containing natural products: structure, bioactivity, and biosynthesis

Covering: 2005 to August, 2023Polyamine-containing natural products (NPs) have been isolated from a wide range of terrestrial and marine organisms and most of them exhibit remarkable and diverse activities, including antimicrobial, antiprotozoal, antiangiogenic, antitumor, antiviral, iron-chelating, anti-depressive, anti-inflammatory, insecticidal, antiobesity, and antioxidant properties. Their extraordinary activities and potential applications in human health and agriculture attract increasing numbers of studies on polyamine-containing NPs. In this review, we summarized the source, structure, classification, bioactivities and biosynthesis of polyamine-containing NPs, focusing on the biosynthetic mechanism of polyamine itself and representative polyamine alkaloids, polyamine-containing siderophores with catechol/hydroxamate/hydroxycarboxylate groups, nonribosomal peptide-(polyketide)-polyamine (NRP-(PK)-PA), and NRP-PK-long chain poly-fatty amine (lcPFAN) hybrid molecules.

Lycium RIN negatively modulate the biosynthesis of kukoamine A in hairy roots through decreasing thermospermine synthase expression

Root bark (Lycii cortex) of Lycium contains high contents of characteristic bioactive compounds, including kukoamine A (KuA) and kukoamine B (KuB). RIPENING INHIBITOR (RIN) is well known as a master regulator of Solanaceaous fruit ripening. However, the role of RIN in the biosynthetic pathway of KuA in Lycium remains unclear. In this study, integrated transcriptomic, metabolomic analyses and hairy root system are used to characterize the role of RIN in KuA biosynthesis in Lycium. The ultra performance liquid chromatography electrospray ionization tandem mass spectrometry analysis revealed that KuA was significantly induced in LrRIN1 RNAi lines and not detected in overexpression lines. A total of 20,913 differentially expressed genes (DEGs) and 60 differentially accumulated metabolites (DAMs) were detected in LrRIN1 transgenic hairy roots, which were used for weighted gene co-expression network analysis. Our result reveals a high association between KuA and structural genes in the phenolamide pathway, which shows a negative correlation with LrRIN1. In addition, overexpression of the polyamine pathway gene thermospermine synthase LcTSPMS, a potential target gene of Lycium RIN, increased the contents of both KuA and KuB in L. chinense hairy root, indicating that TSPMS is responsible for KuA biosynthesis and is also the common upstream biosynthetic gene for both KuA and KuB. Our results lay a solid foundation for uncovering the biosynthetic pathway of KuA, which will facilitate the molecular breeding and genetic improvement of Lycium species.

The untapped potential of spermidine alkaloids: Sources, structures, bioactivities and syntheses

Spermidine alkaloids are a kind of natural products possessing an aliphatic triamine structure with three or four methylene groups between two N-atoms. Spermidine alkaloids exist in plants, microorganisms, and marine organisms, which usually form amide structures with cinnamic acid or fatty acid derivatives. Their unique structures showed a wide range of biological activities such as neuroprotective, anti-aging, anti-cancer, antioxidant, anti-inflammatory, and antimicrobial. In order to better understand the research status of spermidine alkaloids and promote their applications in human health, this paper systematically reviewed the biological sources, structures, pharmacological actions, and synthetic processes of spermidine alkaloids over the past two decades. This will help to open up new pharmacological investigation fields and better drug design based on these spermidine alkaloids.

Function of hydroxycinnamoyl spermidines in seedling growth of Arabidopsis

Hydroxycinnamic acid amides are involved in various developmental processes as well as in biotic and abiotic stress responses. Among them, the presence of spermidine derivatives, such as N1,N8-di(coumaroyl)-spermidine and N1,N8-di(sinapoyl)-spermidine, and their biosynthetic genes have been reported in Arabidopsis, but their functions in plants are still unknown. We chemically synthesized the above-mentioned spermidine derivatives to assess their physiological functions in Arabidopsis. We evaluated the growth and development of chemically treated Arabidopsis and demonstrated that these compounds inhibited seed germination, hypocotyl elongation, and primary root growth, which could be due to modulation of plant hormone homeostasis and signaling. The results suggest that these compounds are regulatory metabolites that modulate plant growth and development.

Solid-Phase Synthesis of Selectively Mono-Fluorobenz(o)ylated Polyamines as a Basis for the Development of 18F-Labeled Radiotracers

Polyamines are highly attractive vectors for tumor targeting, particularly with regards to the development of radiolabeled probes for imaging by positron emission (PET) and single-photon emission computed tomography (SPECT). However, the synthesis of selectively functionalized derivatives remains challenging due to the presence of multiple amino groups of similar reactivity. In this work, we established a synthetic methodology for the selective mono-fluorobenz(o)ylation of various biogenic diamines and polyamines as lead compounds for the perspective development of substrate-based radiotracers for targeting polyamine-specific membrane transporters and enzymes such as transglutaminases. For this purpose, the polyamine scaffold was constructed by solid-phase synthesis of the corresponding oxopolyamines and subsequent reduction with BH₃/THF. Primary and secondary amino groups were selectively protected using Dde and Boc as protecting groups, respectively, in orientation to previously reported procedures, which enabled the selective introduction of the reporter groups. For example, N¹-FBz-spermidine, N⁴-FBz-spermidine, N⁸-FBz-spermidine, and N¹-FBz-spermine and N⁴-FBz-spermine (FBz = 4-fluorobenzoyl) were obtained in good yields by this approach. The advantages and disadvantages of this synthetic approach are discussed in detail and its suitability for radiolabeling was demonstrated for the solid-phase synthesis of N¹-[¹⁸F]FBz-cadaverine.

The isolation of water-soluble natural products - challenges, strategies and perspectives

Covering period: up to 2019Water-soluble natural products constitute a relevant group of secondary metabolites notably known for presenting potent biological activities. Examples are aminoglycosides, β-lactam antibiotics, saponins of both terrestrial and marine origin, and marine toxins. Although extensively investigated in the past, particularly during the golden age of antibiotics, hydrophilic fractions have been less scrutinized during the last few decades. This review addresses the possible reasons on why water-soluble metabolites are now under investigated and describes approaches and strategies for the isolation of these natural compounds. It presents examples of several classes of hydrosoluble natural products and how they have been isolated. Novel stationary phases and chromatography techniques are also reviewed, providing a perspective towards a renaissance in the investigation of water-soluble natural products.

Synthesis and Biological Activities of Naturally Functionalized Polyamines: An Overview

Recently, extensive researches have emphasized the fact that polyamine conjugates are becoming important in all biological and medicinal fields. In this review, we will focus our attention on natural polyamines and highlight recent progress in both fundamental mechanism studies and interests in the development and application for the therapeutic use of polyamine derivatives.

Total synthesis of ent-pavettamine

Pavettamine, a plant toxin first isolated from Pavetta harborii in 1995, was previously identified as a polyamine with C₂ symmetry and a 1,3-syn-diol moiety on a C₁₀ carbon backbone – one of very few substituted polyamines to be isolated from nature. Its absolute configuration was later established by our first reported total synthesis in 2010. Herein we report the first total synthesis of the enantiomer of pavettamine, ent-pavettamine. The symmetrical structure of the molecule allows for the synthesis of a common C₅ fragment that can be divergently transformed into two synthons for later convergent coupling to furnish the target carbon framework. Based on the success of the protocol we employed for the synthesis of the naturally occurring pavettamine, (S)-malic acid was again the starting material of choice for the synthesis of the two individual C₅ fragments, with strategic differences in terminal-group manipulation allowing for the synthesis of ent-pavettamine rather than pavettamine. Chain extension and stereoselective ketone reduction were achieved using the (R)-methyl p-tolyl sulfoxide chiral auxiliary to give the desired 1,3-syn-diol C₅ unit. A protecting-group strategy was also developed for the orthogonal protection of the alcohol and amine functional groups as they were unveiled. The functionalized C₅ fragments were coupled via reductive amination revealing the C₁₀ carbon backbone. Deprotection of the alcohol and amine functional groups successfully provided ent-pavettamine as a TFA salt.

Phenolamides: Plant specialized metabolites with a wide range of promising pharmacological and health-promoting interests

Phenolamides constitute a family of metabolites, widely represented in the plant kingdom, that can be found in all plant organs with a predominance in flowers and pollen grains. They represent a large and structurally diverse family, resulting from the association of phenolic acids with aliphatic or aromatic amines. Initially revealed as active compounds in several medicinal plant extracts, phenolamides have been extensively studied for their health-promoting and pharmacological properties. Indeed, phenolamides have been shown to exhibit antioxidant, anti-inflammatory, anti-cancer and antimicrobial properties, but also protective effects against metabolic syndrome and neurodegenerative diseases. The purpose of this review is to summarise this large body of literature, including in vitro and in vivo studies, by describing the diversity of their biological properties and our actual knowledge of the molecular mechanisms behind them. With regard to their considerable pharmacological interest, the question of industrial production is also tackled through chemical and biological syntheses in engineered microorganisms. The diversity of biological activities already described, together with the active discovery of the broad structural diversity of this metabolite family, make phenolamides a promising source of new active compounds on which future studies should be focused.

Alkaloids of Abuta panurensis Eichler: In silico and in vitro study of acetylcholinesterase inhibition, cytotoxic and immunomodulatory activities

Natural products obtained from species of the genus Abuta (Menispermaceae) are known as ethnobotanicals that are attracting increasing attention due to a wide range of their pharmacological properties. In this study, the alkaloids stepharine and 5-N-methylmaytenine were first isolated from branches of Abuta panurensis Eichler, an endemic species from the Amazonian rainforest. Structure of the compounds was elucidated by a combination of 1D and 2D NMR spectroscopic and MS and HRMS spectrometric techniques. Interaction of the above-mentioned alkaloids with acetylcholinesterase enzyme and interleukins IL-6 and IL-8 was investigated in silico by molecular docking. The molecules under investigation were able to bind effectively with the active sites of the AChE enzyme, IL-6, and IL-8 showing affinity towards the proteins. Along with the theoretical study, acetylcholinesterase enzyme inhibition, cytotoxic, and immunomodulatory activity of the compounds were assessed by in vitro assays. The data obtained in silico corroborate the results of AChE enzyme inhibition, the IC50 values of 61.24μM for stepharine and 19.55μM for 5-N-methylmaytenine were found. The compounds showed cytotoxic activity against two tumor cell lines (K562 and U937) with IC50 values ranging from 11.77 μM to 28.48 μM. The in vitro assays revealed that both alkaloids were non-toxic to Vero and human PBMC cells. As for the immunomodulatory activity, both compounds inhibited the production of IL-6 at similar levels. Stepharine inhibited considerably the production of IL-8 in comparison to 5-N-methylmaytenine, which showed a dose dependent action (inhibitory at the IC50 dose, and stimulatory at the twofold IC50 one). Such a behavior may possibly be explained by different binding modes of the alkaloids to the interleukin structural fragments. Occurrence of the polyamine alkaloid 5-N-methylmaytenine was reported for the first time for the Menispermaceae family, as well as the presence of stepharine in A. panurensis.

VenoMS-A Website for the Low Molecular Mass Compounds in Spider Venoms

Spider venoms are highly complex mixtures. Numerous spider venom metabolites are uniquely found in spider venoms and are of interest concerning their potential use in pharmacology, agriculture, and cosmetics. A nontargeted ultra-high performance high-resolution electrospray tandem mass spectrometry (UHPLC-HR-ESI-MS/MS) approach offers a resource-saving way for the analysis of crude spider venom. However, the identification of known as well as the structure elucidation of unknown low molecular mass spider venom compounds based on their MS/MS spectra is challenging because (1) acylpolyamine toxins are exclusively found in spider and wasp venom, (2) reference MS/MS spectra are missing in established mass spectrometry databases, and (3) trivial names for the various toxin metabolites are used in an inconsistent way in literature. Therefore, we introduce the freely accessible MS website for low molecular mass spider venom metabolites, venoMS, containing structural information, MS/MS spectra, and links to related literature. Currently the database contains the structures of 409 acylpolyamine toxins, 36 free linear polyamines, and 81 additional spider venom metabolites. Implemented into this website is a fragment ion calculator (FRIOC) that allows us to predict fragment ions of linear polyamine derivatives. With three metabolites from the venom of the spider Agelenopsis aperta, it was demonstrated how the new website can support the structural elucidation of acylpolyamines using their MS/MS spectra.

Adaptation of the metabolomics profile of rice after Pyricularia oryzae infection

Pyricularia oryzae (P. oryzae), one of the most devastating fungal pathogens, is the cause of blast disease in rice. Infection with a blast fungus induces biological responses in the host plant that lead to its survival through the termination or suppression of pathogen growth, and metabolite compounds play vital roles in plant interactions with a wide variety of other organisms. Numerous studies have indicated that rice has a multi-layered plant immune system that includes pre-developed (e.g., cell wall and phytoanticipins), constitutive and inducible (phytoalexins) defence barriers against stresses. Significant progress towards understanding the basis of the molecular mechanisms underlying the defence responses of rice to P. oryzae has been achieved. Nonetheless, even though the important metabolites in the responses of rice to pathogens have been identified, their exact mechanisms and their contributions to plant immunity against blast fungi have not been elucidated. The purpose of this review is to summarize and discuss recent advances towards the understanding of the integrated metabolite variations in rice after P. oryzae invasion.

Gardenifolins A-H, Scalemic Neolignans from Gardenia ternifolia: Chiral Resolution, Configurational Assignment, and Cytotoxic Activities against the HeLa Cancer Cell Line

From the tropical plant Gardenia ternifolia Schumach. and Thonn. (Rubiaceae), eight stereoisomeric 2,3-dihydrobenzo[b]furan neolignans, named gardenifolins A-H (1a-d and 2a-d), were isolated and fully structurally characterized. Reversed-phase chromatography of a stem bark extract afforded two peaks, viz. mixtures I and II, each one consisting of two diastereomers and their respective enantiomers. They were resolved and stereochemically analyzed by HPLC on a chiral phase coupled to electronic circular dichroism (ECD) spectroscopy, giving single ECD spectra of all eight stereoisomers. The double-bond geometries (E or Z) of the gardenifolins A-H and their relative configurations (cis or trans) at the stereogenic centers C-7 and C-8 in the dihydrofuran ring system were assigned by 1D and 2D NMR methods, in particular, using NOE difference experiments, whereas the absolute configurations of the isolated enantiomers were established by ECD spectroscopy by applying the reversed helicity rule. The individual pure gardenifolin isomers A-H showed the most different cytotoxic effects against the human cancer HeLa cell line, with 1d and 2a displaying the highest activities, with IC₅₀ values of 21.0 and 32.5 μM, respectively. Morphological experiments indicated that gardenifolin D (1d) induces apoptosis of HeLa cells at 25 μM.

Practical Synthesis of Spermine, Thermospermine and Norspermine

Polyamines, such as spermine (1), thermospermine (2) and norspermine (3), are widely distributed in nature, and have multiple biological activities. In addition, many of their conjugates have potential for pharmacological use. Here, we present a solid-phase synthesis using our nitrobenzenesulfonyl (Ns) strategy, which can provide 1, 2 and 3 on a gram scale. This approach should be suitable for facile construction of a diverse library of polyamines.

A new spermidine macrocyclic alkaloid isolated from Gymnosporia arenicola leaf

The isolation and structural elucidation of a macrocyclic alkaloid, characterized by the presence of a 13-membered macrolactam ring containing a spermidine unit N-linked to a benzoyl group is hereby reported. The structure of this previously unknown spermidine alkaloid isolated from Gymnosporia arenicola (Celastraceae) leaves has been elucidated by (1)H and (13)C NMR spectroscopy (including bidimensional analysis) and further characterized by high-resolution mass spectrometry and polarimetry. A route for the biosynthesis of this new bioactive macrocycle is proposed and the cytotoxicity of the compound was evaluated against two ATCC cell lines - one normal-derived (MCF10A) and one cancer-derived cell line (MCF7) - using the MTT assay. The alkaloid revealed to be non-cytotoxic against both cell lines. The IC50 values from the cells were also determined.

Spatiotemporal distribution of phenolamides and the genetics of natural variation of hydroxycinnamoyl spermidine in rice

Phenolamides constitute a diverse class of secondary metabolites that are found ubiquitously in plants and have been implicated to play an important role in a wide range of biological processes, such as plant development and defense. However, spatiotemporal accumulation patterns of phenolamides in rice, one of the most important crops, are not available, and no gene responsible for phenolamide biosynthesis has been identified in this species. In this study, we report the comprehensive metabolic profiling and natural variation analysis of phenolamides in a collection of rice germplasm using a liquid chromatography-mass spectrometry-based targeted metabolomics method. Spatiotemporal controlled accumulations were observed for most phenolamides, together with their differential accumulations between the two major subspecies of rice. Further metabolic genome-wide association study (mGWAS) in rice leaf and in vivo metabolic analysis of the transgenic plants identified Os12g27220 and Os12g27254 as two spermidine hydroxycinnamoyl transferases that might underlie the natural variation of levels of spermidine conjugates in rice. Our work demonstrates that gene-to-metabolite analysis by mGWAS provides a useful tool for functional gene identification and omics-based crop genetic improvement.

Investigation of indolglyoxamide and indolacetamide analogues of polyamines as antimalarial and antitrypanosomal agents

Pure compound screening has previously identified the indolglyoxylamidospermidine ascidian metabolites didemnidine A and B (2 and 3) to be weak growth inhibitors of Trypanosoma brucei rhodesiense (IC₅₀ 59 and 44 μM, respectively) and Plasmodium falciparum (K1 dual drug resistant strain) (IC₅₀ 41 and 15 μM, respectively), but lacking in selectivity (L6 rat myoblast, IC₅₀ 24 μM and 25 μM, respectively). To expand the structure–activity relationship of this compound class towards both parasites, we have prepared and biologically tested a library of analogues that includes indoleglyoxyl and indoleacetic “capping acids”, and polyamines including spermine (PA3-4-3) and extended analogues PA3-8-3 and PA3-12-3. 7-Methoxy substituted indoleglyoxylamides were typically found to exhibit the most potent antimalarial activity (IC₅₀ 10–92 nM) but with varying degrees of selectivity versus the L6 rat myoblast cell line. A 6-methoxyindolglyoxylamide analogue was the most potent growth inhibitor of T.brucei (IC₅₀ 0.18 μM) identified in the study: it, however, also exhibited poor selectivity (L6 IC₅₀ 6.0 μM). There was no apparent correlation between antimalarial and anti-T. brucei activity in the series. In vivo evaluation of one analogue against Plasmodium berghei was undertaken, demonstrating a modest 20.9% reduction in parasitaemia.

Macrocyclic spermidine alkaloids from Androya decaryi L. Perrier

Three new spermidine alkaloids and two known compounds were isolated from the leaves of Androya decaryi. Their structures were elucidated on the basis of their spectroscopic data (NMR and mass spectrometry), by X-Ray diffraction and by comparison with literature values. Evaluation of the in vitro antiplamosdial properties of the isolated compounds revealed they did not possess any significant activity.

Tissue-specific distribution of secondary metabolites in rapeseed (Brassica napus L.)

Four different parts, hypocotyl and radicle (HR), inner cotyledon (IC), outer cotyledon (OC), seed coat and endosperm (SE), were sampled from mature rapeseed (Brassica napus L.) by laser microdissection. Subsequently, major secondary metabolites, glucosinolates and sinapine, as well as three minor ones, a cyclic spermidine conjugate and two flavonoids, representing different compound categories, were qualified and quantified in dissected samples by high-performance liquid chromatography with diode array detection and mass spectrometry. No qualitative and quantitative difference of glucosinolates and sinapine was detected in embryo tissues (HR, IC and OC). On the other hand, the three minor compounds were observed to be distributed unevenly in different rapeseed tissues. The hypothetic biological functions of the distribution patterns of different secondary metabolites in rapeseed are discussed.

Didemnidines A and B, indole spermidine alkaloids from the New Zealand ascidian Didemnum sp

Two new indole spermidine alkaloids, didemnidines A (1) and B (2), have been isolated from the New Zealand ascidian Didemnum sp. The structures of the metabolites, determined by analysis of 2D NMR spectra and confirmed via synthesis, embody an indole-3-glyoxylamide moiety linked to the N(1) position of spermidine, the latter motif being particularly rare among marine natural products. Didemnidine B and a synthetic precursor exhibited mild in vitro growth inhibition of Plasmodium falciparum with IC(50)'s of 15 and 8.4 μM, respectively.

Meehanines L-W, spermidine alkaloidal glycosides from Meehania urticifolia

Twelve new spermidine alkaloidal glycosides, meehanines L-W (1-12), were isolated from the whole plant Meehania urticifolia. The structures of these new compounds were elucidated on the basis of spectroscopic data analyses.

A novel polyamine acyltransferase responsible for the accumulation of spermidine conjugates in Arabidopsis seed

Hydroxycinnamic acid amides are a class of secondary metabolites distributed widely in plants. We have identified two sinapoyl spermidine derivatives, N-((4'-O-glycosyl)-sinapoyl),N'-sinapoylspermidine and N,N'-disinapoylspermidine, which comprise the two major polyamine conjugates that accumulate in Arabidopsis thaliana seed. Using metabolic profiling of knockout mutants to elucidate the functions of members of the BAHD acyltransferase family in Arabidopsis, we have also identified two genes encoding spermidine disinapoyl transferase (SDT) and spermidine dicoumaroyl transferase (SCT) activities. At2g23510, which is expressed mainly in seeds, encodes a spermidine sinapoyl CoA acyltransferase (SDT) that is required for the production of disinapoyl spermidine and its glucoside in Arabidopsis seed. The structurally related BAHD enzyme encoded by At2g25150 is expressed specifically in roots and has spermidine coumaroyl CoA acyltransferase (SCT) activity both in vitro and in vivo.

Highway or byway: the metabolic role of the GABA shunt in plants

Much of the recent work on the gamma-aminobutyrate (GABA) shunt in plants has concentrated on stress/pest-associated and signalling roles. However, fifty years after the structural elucidation of the pathway, aspects of its regulation and even of its biological significance remain largely obscure. Here, we assess the importance of GABA metabolism in plants, reviewing relevant biological circumstances and taking advantage of high-throughput data accessibility and computational approaches. We discuss the premise that GABA metabolism plays a major role in carbon and nitrogen primary metabolism. We further evaluate technological developments that will likely allow us to address the quantitative importance of this shunt within the biological processes to which it contributes.

Polyamines: metabolism to systems biology and beyond

Polyamines and the metabolic and physiopathological processes in which they are involved represent an active field of research that has been continuously growing since the seventies. In the last years, the trends in the focused areas of interest within this field since the 1970s have been confirmed. The impact of "-omics" in polyamine research remains too low in comparison with its deep impact on other biological research areas. These high-throughput approaches, along with systems biology and, in general, more systemic and holistic approaches should contribute to a renewal of this research area in the near future.

Recent progress on the total synthesis of natural products in China

An overview of natural products synthesis in Mainland China during the past 10 years is provided. This review only emphasizes the first total synthesis of molecules of contemporary interest and syntheses that helped to correct structures. In addition, some significant results on the novel synthesis and structure-activity relationship (SAR) studies of several natural products are introduced.

Dovyalicin-type spermidine alkaloids from Dovyalis species

Phytochemical investigations of Dovyalis abyssinica, D. hebecarpa, and D. macrocalyx revealed two new spermidine-type alkaloids, dovyalicin E (3) and dovyalicin F (4), along with the previously described dovyalicin A (1), dovyalicin B (2), and dovyalicin C (5). In addition, a new phenol glucoside, 4-hydroxytremulacin (7), and the new 1,2-cyclohexanediol glucoside 9, as well as the known compounds methyl 1-hydroxy-6-oxocyclohex-2-enecarboxylate (6) and tremulacin (8), were isolated. The structures were established using homo- and heteronuclear two-dimensional NMR experiments and chiroptical methods. At ambient temperature, the N-disubstituted amide 4 exists as a mixture of cis and trans conformers. Variable-temperature (1)H NMR studies showed that time-averaged spectra are obtainable at 348 K, and the activation parameters determined for the rotation about the amide bond were DeltaH++ = 89 +/- 4.6 kJ/mol, DeltaS++ = 65 +/- 14 kJ/mol.K, and DeltaG++(298K) = 70 +/- 4.5 kJ/mol.