Chemistry and biology of calystegines

Dereplication of calystegines in food plants and wild Solanum Brazilian fruits

Calystegines are potent glycosidase inhibitors with therapeutic potential and are constituents of food and feed with potential toxic effects. This study aims to target calystegines and other nitrogenous substances in food plants. Hydroalcoholic extracts from Solanum tuberosum, Ipomoea batatas, S. lycocarpum, and fruit from S. lycopersicum, S. aethiopicum, S. paniculatum, S. crinitum, and S. acanthodes were analyzed by liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) using an acidic HILIC column. The dereplication approach included data processing using MZMine2, FBMN-GNPS, and structure elucidation and interpretation of the organized data. The calystegines A3, A5, B2, and C1 were identified, and several potential new calystegine analogues: three may correspond to new calystegines of the A-group, one glycosyl derivative of calystegine A3, and two glycosyl derivatives of the B-group. These findings help to direct the search for new calystegines. In addition, the dereplication approach enabled the annotation of 22 other nitrogen compounds.

Discovering a mitochondrion-localized BAHD acyltransferase involved in calystegine biosynthesis and engineering the production of 3β-tigloyloxytropane

Solanaceous plants produce tropane alkaloids (TAs) via esterification of 3α- and 3β-tropanol. Although littorine synthase is revealed to be responsible for 3α-tropanol esterification that leads to hyoscyamine biosynthesis, the genes associated with 3β-tropanol esterification are unknown. Here, we report that a BAHD acyltransferase from Atropa belladonna, 3β-tigloyloxytropane synthase (TS), catalyzes 3β-tropanol and tigloyl-CoA to form 3β-tigloyloxytropane, the key intermediate in calystegine biosynthesis and a potential drug for treating neurodegenerative disease. Unlike other cytosolic-localized BAHD acyltransferases, TS is localized to mitochondria. The catalytic mechanism of TS is revealed through molecular docking and site-directed mutagenesis. Subsequently, 3β-tigloyloxytropane is synthesized in tobacco. A bacterial CoA ligase (PcICS) is found to synthesize tigloyl-CoA, an acyl donor for 3β-tigloyloxytropane biosynthesis. By expressing TS mutant and PcICS, engineered Escherichia coli synthesizes 3β-tigloyloxytropane from tiglic acid and 3β-tropanol. This study helps to characterize the enzymology and chemodiversity of TAs and provides an approach for producing 3β-tigloyloxytropane.

Tropinone reductase: A comprehensive review on its role as the key enzyme in tropane alkaloids biosynthesis

TAs, including hyoscyamine and scopolamine, were used to treat neuromuscular disorders ranging from nerve agent poisoning to Parkinson's disease. Tropinone reductase I (TR-I; EC 1.1.1.206) catalyzed the conversion of tropinone into tropine in the biosynthesis of TAs, directing the metabolic flow towards hyoscyamine and scopolamine. Tropinone reductase II (TR-II; EC 1.1.1.236) was responsible for the conversion of tropinone into pseudotropine, diverting the metabolic flux towards calystegine A3. The regulation of metabolite flow through both branches of the TAs pathway seemed to be influenced by the enzymatic activity of both enzymes and their accessibility to the precursor tropinone. The significant interest in the utilization of metabolic engineering for the efficient production of TAs has highlighted the importance of TRs as crucial enzymes that govern both the direction of metabolic flow and the yield of products. This review discussed recent advances for the TRs sources, properties, protein structure and biocatalytic mechanisms, and a detailed overview of its crucial role in the metabolism and synthesis of TAs was summarized. Furthermore, we conducted a detailed investigation into the evolutionary origins of these two TRs. A prospective analysis of potential challenges and applications of TRs was presented.

The rise and fall of mandrake in medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Mandrake (Mandragora sp.) is one of the most famous medicinal plants. It has been in continuous medical use throughout written history and is still in use today in popular medicine.

AIM OF THE STUDY

Mandrake derived drugs once played an important role in medicine and in magical practices. Today, the role of mandrake in popular medicine is marginal. However, natural products present in mandrake such as atropine and scopolamine, as well as their semi synthetic derivatives continue to hold and important role in medicine. Here we aim to trace the development of historical rationales and scientific events that led to the abandonment of mandrake as a medicine.

MATERIALS AND METHODS

We review the medicinal uses of mandrake drugs since antiquity in an attempt to pinpoint use patterns that were popular in certain periods of time and others that are more general. We compare the uses from the native territories to those from regions where the plant got introduced and use literature reporting mandrake's chemistry and pharmacology in order to explain the diachronic changes of use patterns.

RESULTS AND CONCLUSION

We found information about 88 different medicinal uses for mandrake, grouped into 39 conditions. According to the number of different medicinal uses, the most versatile period was the medieval (37), followed by the Renaissance (31), the classical (27), and the modern period (21). Considering the higher number of textual sources and use-records collected for the Renaissance period, the decrease of versatility in comparison to the medieval period appears robust. This seems to indicate a more consolidated use pattern, that might be conditioned by the reproduction of classic textual sources as well as by a less experimental approach and reduced popularity of mandrake in medicine. The introduction of the volatile anaesthetics with more reliable narcotic effects set the seal on using mandrake in surgery but opened the way for atropine being used as a prophylactic and antidote during surgical interventions.

Emerging Issues on Tropane Alkaloid Contamination of Food in Europe

The occurrence of tropane alkaloids (TAs), toxic plant metabolites, in food in Europe was studied to identify those TAs in food most relevant for human health. Information was extracted from the literature and the 2016 study from the European Food Safety Authority. Calystegines were identified as being inherent TAs in foods common in Europe, such as Solanum tuberosum (potato), S. melongena (eggplant, aubergine), Capsicum annuum (bell pepper) and Brassica oleracea (broccoli, Brussels sprouts). In addition, some low-molecular-weight tropanes and Convolvulaceae-type TAs were found inherent to bell pepper. On the other hand, atropine, scopolamine, convolvine, pseudotropine and tropine were identified as emerging TAs resulting from the presence of associated weeds in food. The most relevant food products in this respect are unprocessed and processed cereal-based foods for infants, young children or adults, dry (herbal) teas and canned or frozen vegetables. Overall, the occurrence data on both inherent as well as on associated TAs in foods are still scarce, highlighting the need for monitoring data. It also indicates the urge for food safety authorities to work with farmers, plant breeders and food business operators to prevent the spreading of invasive weeds and to increase awareness.

The powerful Solanaceae: Food and nutraceutical applications in a sustainable world

The Solanaceae family is considered one of the most important families among plant species because, on one hand encompasses many staple food crops of the human diet while, on the other hand, it includes species rich in powerful secondary metabolites that could be valorized in medicine or drug formulation as well as nutraceuticals and food supplements. The main genera are Solanum, Capsicum, Physalis, and Lycium which comprise several important cultivated crops (e.g., tomato, pepper, eggplant, tomatillo, and goji berry), as well as genera notable for species with several pharmaceutical properties (e.g., Datura, Nicotiana, Atropa, Mandragora, etc.). This chapter discusses the nutritional value of the most important Solanaceae species commonly used for their edible fruit, as well as those used in the development of functional foods, food supplements, and nutraceuticals due to their bioactive constituents. The toxic and poisonous effects are also discussed aiming to highlight possible detrimental consequences due to irrational use. Finally, considering the high amount of waste and by-products generated through the value chain of the main crops, the sustainable management practices implemented so far are presented with the aim to increase the added-value of these crops.

Interaction With Fungi Promotes the Accumulation of Specific Defense Molecules in Orchid Tubers and May Increase the Value of Tubers for Biotechnological and Medicinal Applications: The Case Study of Interaction Between Dactylorhiza sp. and Tulasnella calospora

Terrestrial orchids can form tubers, organs modified to store energy reserves. Tubers are an attractive source of nutrients, and salep, a flour made from dried orchid tubers, is the source of traditional beverages. Tubers also contain valuable secondary metabolites and are used in traditional medicine. The extensive harvest of wild orchids is endangering their populations in nature; however, orchids can be cultivated and tubers mass-produced. This work illustrates the importance of plant-fungus interaction in shaping the content of orchid tubers in vitro. Orchid plants of Dactylorhiza sp. grown in asymbiotic culture were inoculated with a fungal isolate from Tulasnella calospora group and, after 3 months of co-cultivation, tubers were analyzed. The fungus adopted the saprotrophic mode of life, but no visible differences in the morphology and biomass of the tubers were detected compared to the mock-treated plants. To elucidate the mechanisms protecting the tubers against fungal infestation, proteome, metabolome, and lipidome of tubers were analyzed. In total, 1,526, 174, and 108 proteins, metabolites, and lipids were quantified, respectively, providing a detailed snapshot of the molecular process underlying plant-microbe interaction. The observed changes at the molecular level showed that the tubers of inoculated plants accumulated significantly higher amounts of antifungal compounds, including phenolics, alkaloid Calystegine B2, and dihydrophenanthrenes. The promoted antimicrobial effects were validated by observing transient inhibition of Phytophthora cactorum growth. The integration of omics data highlighted the promotion of flavonoid biosynthesis, the increase in the formation of lipid droplets and associated production of oxylipins, and the accumulation of auxin in response to T. calospora. Taken together, these results provide the first insights into the molecular mechanisms of defense priming in orchid tubers and highlight the possible use of fungal interactors in biotechnology for the production of orchid secondary metabolites.

Cyclisations and Strategies for Stereoselective Synthesis of Piperidine Iminosugars

This personal account focuses on synthesis of polyhydroxylated piperidines, a subset of compounds within the iminosugar family. Cyclisations to form the piperidine ring include reductive amination, substitution via amines, iminium ions and cyclic nitrones, transamidification (N-acyl transfer), addition to alkenes, ring contraction and expansion, photoinduced electron transfer, multicomponent Ugi reaction and ring closing metathesis. Enantiomerically pure piperidines are obtained from chiral pool precursors (e. g. sugars, amino acids, Garner's aldehyde) or asymmetric reactions (e. g. epoxidation, dihydroxylation, aminohydroxylation, aldol, biotransformation). Our laboratory have contributed cascades based on reductive amination from glycosyl azide precursors as well as Huisgen azide-alkene cycloaddition. The latter's combination with allylic azide rearrangement has given substituted piperidines, including those with quaternary centres adjacent to nitrogen.

Alkaloids of the Genus Datura: Review of a Rich Resource for Natural Product Discovery

The genus Datura (Solanaceae) contains nine species of medicinal plants that have held both curative utility and cultural significance throughout history. This genus’ particular bioactivity results from the enormous diversity of alkaloids it contains, making it a valuable study organism for many disciplines. Although Datura contains mostly tropane alkaloids (such as hyoscyamine and scopolamine), indole, beta-carboline, and pyrrolidine alkaloids have also been identified. The tools available to explore specialized metabolism in plants have undergone remarkable advances over the past couple of decades and provide renewed opportunities for discoveries of new compounds and the genetic basis for their biosynthesis. This review provides a comprehensive overview of studies on the alkaloids of Datura that focuses on three questions: How do we find and identify alkaloids? Where do alkaloids come from? What factors affect their presence and abundance? We also address pitfalls and relevant questions applicable to natural products and metabolomics researchers. With both careful perspectives and new advances in instrumentation, the pace of alkaloid discovery—from not just Datura—has the potential to accelerate dramatically in the near future.

Stereoselective Synthesis of Tropanes via a 6π-Electrocyclic Ring-Opening/ Huisgen [3+2]-Cycloaddition Cascade of Monocyclopropanated Heterocycles

The synthesis of tropanes via a microwave-assisted, stereoselective 6π-electrocyclic ring-opening/ Huisgen [3+2]-cycloaddition cascade of cyclopropanated pyrrole and furan derivatives with electron-deficient dipolarophiles is demonstrated. Starting from furans or pyrroles, 8-aza- and 8-oxabicyclo[3.2.1]octanes are accessible in two steps in dia- and enantioselective pure form, being versatile building blocks for the synthesis of pharmaceutically relevant targets, especially for new cocaine analogues bearing various substituents at the C-6/C-7 positions of the tropane ring system. Moreover, the 2-azabicyclo[2.2.2]octane core (isoquinuclidines), being prominently represented in many natural and pharmaceutical products, is accessible via this approach.

Recent applications of the Wittig reaction in alkaloid synthesis

The Wittig reaction is the chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide (the Wittig reagent) to afford an alkene and triphenylphosphine oxide. Noteworthy, this reaction results in the synthesis of alkenes in a selective and predictable fashion. Thus, it became as one of the keystone of synthetic organic chemistry, especially in the total synthesis of natural products, where the selectivity of a reaction is paramount of importance. A literature survey disclosed the existence of vast numbers of related reports and comprehensive reviews on the applications of this important name reaction in the total synthesis of natural products. However, the aim of this chapter is to underscore, the applications of the Wittig reaction in the total synthesis of one the most important and prevalent classes of natural products, the alkaloids, especially those showing important and diverse biological activities.

Charting Angiosperm Chemistry: Evolutionary Perspective on Specialized Metabolites Reflected in Chemical Property Space

Plants possess an outstanding chemical diversity of specialized metabolites developed to adapt to environmental niches and increase fitness. The observed diversity is hypothesized to result from various evolutionary mechanisms, such as the continuous branching off and extension of existing biosynthetic pathways or enhanced levels of catalytic promiscuity in certain enzymes. In this study, ChemGPS-NP has been employed to chart the distribution and diversity of physicochemical properties for selected types of specialized metabolites from the angiosperms. Utilizing these charts, it is analyzed how different properties of various types of specialized metabolites change in different plant groups, and the chemical diversity from the volume they occupy in chemical property space is evaluated. In this context, possible underlying evolutionary mechanisms are discussed, which could explain the observed distribution and behavior in chemical property space. Based on these studies, it is demonstrated that evolutionary processes in plant specialized metabolism and the resultant metabolic diversification are reflected in chemical property space.

Nicotine Biosynthesis inNicotiana: A Metabolic Overview

Alkaloids are important compounds found in Nicotiana plants, essential in plant defense against herbivores. The main alkaloid of Nicotiana tabacum, nicotine, is produced in roots and translocated to the leaves. Nicotine is formed by a pyrrolidine and a pyridine ring in a process involving several enzymes. The pyridine ring of nicotine is derived from nicotinic acid, whereas the pyrrolidine ring originates from polyamine putrescine metabolism. After synthesis in root cortical cells, a set of transporters is known to transport nicotine upward to the aerial part and store it in leaf vacuoles. Moreover, nicotine can be metabolized in leaves, giving rise to nornicotine through the N-demethylation process. Some Nicotiana wild species produce acyltransferase enzymes, which allow the plant to make N-acyl-nornicotine, an alkaloid with more potent insecticidal properties than nicotine. However, although we can find a wealth of information about the alkaloid production in Nicotiana spp., our understanding about nicotine biosynthesis, transport, and metabolism is still incomplete. This review will summarize these pathways on the basis on recent literature, as well as highlighting questions that need further investigation.

Tropane Alkaloids: Chemistry, Pharmacology, Biosynthesis and Production

Tropane alkaloids (TA) are valuable secondary plant metabolites which are mostly found in high concentrations in the Solanaceae and Erythroxylaceae families. The TAs, which are characterized by their unique bicyclic tropane ring system, can be divided into three major groups: hyoscyamine and scopolamine, cocaine and calystegines. Although all TAs have the same basic structure, they differ immensely in their biological, chemical and pharmacological properties. Scopolamine, also known as hyoscine, has the largest legitimate market as a pharmacological agent due to its treatment of nausea, vomiting, motion sickness, as well as smooth muscle spasms while cocaine is the 2nd most frequently consumed illicit drug globally. This review provides a comprehensive overview of TAs, highlighting their structural diversity, use in pharmaceutical therapy from both historical and modern perspectives, natural biosynthesis in planta and emerging production possibilities using tissue culture and microbial biosynthesis of these compounds.

Building Microbial Hosts for Heterologous Production of N-Methylpyrrolinium

N-Methylpyrrolinium-derived alkaloids like tropane alkaloids, nicotine, and calystegines are valuable plant source specialized metabolites bearing pharmaceutical or biological activity. Microbial synthesis of the critical common intermediate N-methylpyrrolinium would allow for sustainable production of N-methylpyrrolinium-derived alkaloids. Here, we achieve the production of N-methylpyrrolinium both in Escherichia coli and in Saccharomyces cerevisiae by employing the biosynthetic genes derived from three different plants. Specifically, the diamine oxidases (DAOs) from Anisodus acutangulus were first characterized. Then, we produced N-methylpyrrolinium in vitro from l-ornithine via a combination of the three cascade enzymes, ornithine decarboxylase from Erythroxylum coca, putrescine N-methyltransferase from Anisodus tanguticus, and DAOs from A. acutangulus. Construction of the plant biosynthetic pathway in E. coli and S. cerevisiae resulted in de novo bioproduction of N-methylpyrrolinium with titers of 3.02 and 2.07 mg/L, respectively. Metabolic engineering of the yeast strain to produce N-methylpyrrolinium via decreasing the flux to the product catabolism pathway and improving the cofactor supply resulted in a final titer of 17.82 mg/L. This study not only presents the first microbial synthesis of N-methylpyrrolinium but also lays the foundation for heterologous biosynthesis of N-methylpyrrolinium-derived alkaloids. More importantly, the strains constructed herein can serve as important alternative tools for identifying undiscovered pathway enzymes with a synthetic biology strategy.

The genus Datura L. (Solanaceae) in Mexico and Spain - Ethnobotanical perspective at the interface of medical and illicit uses

ETHNOPHARMACOLOGICAL RELEVANCE

The different species of the genus Datura have been used traditionally by some pre-Columbian civilizations, as well as in medieval rituals linked to magic and witchcraft in both Mexico and Europe. It is also noteworthy the use of different alkaloids obtained from the plants for medicinal purposes in the treatment of various groups of diseases, especially of the respiratory and muscularskeletal systems.

AIM OF THE STUDY

A review of the ethnobotanical uses of the genus Datura in Mexico and Spain has been conducted. We focus on the medicinal and ritualistic uses included in modern ethnobotanical studies, emphasizing the historical knowledge from post-colonial American Codices and medieval European texts. Datura's current social emergency as a drug of recreation and leisure, as well as its link to crimes of sexual abuse is also considered. The work is completed with some notes about the distribution and ecology of the different species and a phytochemical and pharmacological review of Datura alkaloids, necessary to understand their arrival in Europe and the ethnobotanical uses made since then MATERIALS AND METHODS: A literature review and compilation of information on traditional medicinal uses of the genus has been carried out from the main electronic databases. Traditional volumes (codices) have also been consulted in libraries of different institutions. Consultations have been made with the National Toxicological Services of Spain and Mexico for toxicological data.

RESULTS

A total of 118 traditional uses were collected in both territories, 111 medicinal ones to be applied in 76 conditions or symptoms included in 13 pathological groups. Although there are particular medicinal uses in the two countries, we found up to 15 similar uses, of which 80% were previously mentioned in post-Colonial American codices. Applications in the treatment of asthma and rheumatism are also highlighted. Apart from medicinal uses, it is worth noting their cultural and social uses, in the case of Mexico relating to diseases such as being scared, astonishment or falling in love, and in the case of Spain, as a recreational drug and lately, for criminal purposes.

CONCLUSIONS

This review highlights the variety of uses traditionally given to the different species in both territories. The fact that most of the coincident or similar uses in both countries also appear in the classical codices can be found an example of the flow, not only of the plants from America to Europe, but also of their associated information. It is also relevant that particular uses have derived in both countries, reflecting the difference in the cultural factors and traditions linked to rituals and cultural practices. Finally, the significant growth of Datura consumption in recent years as a drug of leisure and recreation, as well as in crimes of sexual submission, should be considered as research of maximum relevance in the field of forensic botany and toxicology.

Tuning protein folding in lysosomal storage diseases: the chemistry behind pharmacological chaperones

Misfolding of proteins is the basis of several proteinopathies. Chemical and pharmacological chaperones are small molecules capable of inducing the correct conformation of proteins, thus being of interest for human therapeutics. The most recent developments in medicinal chemistry and in the drug development of pharmacological chaperones are discussed, with focus on lysosomal storage diseases.

Palladium-Catalyzed Double Allylation of Sugar-Imines by Employing Tamaru-Kimura's Protocol: Access to Unnatural Iminosugars

Conversion of vinyl pyranosylamine and vinyl furanosylamines to 2,6- and 2,5-disubstituted pyrrolidine and piperidine iminosugars, respectively, in one pot was developed using Kimura and Tamaru's procedure, where a Pd salt in the presence of Et₂Zn was used for the domino reaction. In this procedure, double allylation, which involves nucleophilic allylation-heterocyclization, took place to give desired nitrogen heterocycles. This strategy was further elaborated to synthesize some unnatural deoxycalystegines, hydroxylated pyrrolidines, piperidines, and indolizidine analogues.

Concise synthesis of calystegines B2 and B3via intramolecular Nozaki-Hiyama-Kishi reaction

The key step in the concise syntheses of calystegine B2 and its C-2 epimer calystegine B3 was the construction of cycloheptanone 8via an intramolecular Nozaki-Hiyama-Kishi (NHK) reaction of 9, an aldehyde containing a Z-vinyl iodide. Vinyl iodide 9 was obtained by the Stork olefination of aldehyde 10, derived from carbohydrate starting materials. Calystegines B2 (3) and B3 (4) were synthesized from d-xylose and l-arabinose derivatives respectively in 11 steps in excellent overall yields (27% and 19%).

Tropane alkaloids and calystegines as chemotaxonomic markers in the Solanaceae

ABSTRACT This study assessed the occurrence and distribution of tropane alkaloids and calystegines in genera of the family Solanaceae to identify patterns of distribution and make evolutionary inferences. A database of tropane alkaloids and calystegines occurrences was constructed from the results of a search of scientific websites and a hand search of periodicals. The terms "Solanaceae", "tropane alkaloids", and "calystegines" were used as index terms for a full-text article search unrestricted by date of publications. The number of occurrence and chemical diversity indices were calculated and cluster analysis and principal components analysis were performed. Overall, 996 occurrences were reported, 879 of tropane alkaloids (88.3%) and 117 of calystegines (11.7%). The calystegines were significantly more relevant than tropane alkaloids for characterization of distinct groups of genera on both analyses performed here. This corroborates the trend toward a chemical dichotomy observed on database analysis and somewhat reinforces the correlation between geographic distribution and occurrence of secondary metabolites, as the presence of calystegines alone (without tropane alkaloids) was only reported in genera that have South America as their center of diversity.

Synthesis and evaluation of galacto-noeurostegine and its 2-deoxy analogue as glycosidase inhibitors

An epimer of the known glycosidase inhibitor noeurostegine, galacto-noeurostegine, was synthesised in 21 steps from levoglucosan and found to be a potent, competitive and highly selective galactosidase inhibitor of Aspergillus oryzae β-galactosidase.

A root-expressed L-phenylalanine:4-hydroxyphenylpyruvate aminotransferase is required for tropane alkaloid biosynthesis in Atropa belladonna

The tropane alkaloids, hyoscyamine and scopolamine, are medicinal compounds that are the active components of several therapeutics. Hyoscyamine and scopolamine are synthesized in the roots of specific genera of the Solanaceae in a multistep pathway that is only partially elucidated. To facilitate greater understanding of tropane alkaloid biosynthesis, a de novo transcriptome assembly was developed for Deadly Nightshade (Atropa belladonna). Littorine is a key intermediate in hyoscyamine and scopolamine biosynthesis that is produced by the condensation of tropine and phenyllactic acid. Phenyllactic acid is derived from phenylalanine via its transamination to phenylpyruvate, and mining of the transcriptome identified a phylogenetically distinct aromatic amino acid aminotransferase (ArAT), designated Ab-ArAT4, that is coexpressed with known tropane alkaloid biosynthesis genes in the roots of A. belladonna. Silencing of Ab-ArAT4 disrupted synthesis of hyoscyamine and scopolamine through reduction of phenyllactic acid levels. Recombinant Ab-ArAT4 preferentially catalyzes the first step in phenyllactic acid synthesis, the transamination of phenylalanine to phenylpyruvate. However, rather than utilizing the typical keto-acid cosubstrates, 2-oxoglutarate, pyruvate, and oxaloacetate, Ab-ArAT4 possesses strong substrate preference and highest activity with the aromatic keto-acid, 4-hydroxyphenylpyruvate. Thus, Ab-ArAT4 operates at the interface between primary and specialized metabolism, contributing to both tropane alkaloid biosynthesis and the direct conversion of phenylalanine to tyrosine.

Molecular evolution of N-methylputrescine oxidase in tobacco

Biosynthesis of nicotine in tobacco requires N-methylputrescine oxidase (MPO), which belongs to the copper-containing amine oxidase superfamily. Previous studies identified tobacco MPO1 and its close homolog NtDAO1 (formerly called MPO2), of which MPO1 has been shown preferentially to oxidize N-methylated amines. We show here that NtDAO1, as well as a homologous Arabidopsis diamine oxidase (DAO), accept non-N-methylated amines more efficiently than their corresponding N-methylated amines. MPO1 is coordinately regulated with other nicotine biosynthesis genes with regard to COI1-MYC2-dependent jasmonate induction and its dependence on nicotine-specific ERF transcription factors, whereas NtDAO1 is constitutively expressed at low basal levels in tobacco plants. Both MPO1 and NtDAO1 are targeted to peroxisomes by their C-terminal motifs, and the peroxisomal localization of MPO1 is required for it to function in nicotine biosynthesis in jasmonate-elicited cultured tobacco cells. Restricted occurrence of the MPO subfamily in Nicotiana and Solanum indicates that, during the formation of the Solanaceae, MPO has evolved from a DAO, which functions in polyamine catabolism within peroxisomes, by optimizing substrate preference and gene expression patterns to be suitable for alkaloid formation.

New methodologies for the extraction and fractionation of bioactive carbohydrates from mulberry (Morus alba) leaves

Pressurized liquid extraction (PLE) was applied for the first time to extract bioactive low molecular weight carbohydrates (iminosugars and inositols) from mulberry ( Morus alba ) leaves. Under optimized conditions, PLE provided a similar yield to the conventional process used to extract these bioactives, but in less time (5 vs 90 min). To remove carbohydrates that interfere with the bioactivity of iminosugars from PLE extracts, two fractionation treatments were evaluated: yeast ( Saccharomyces cerevisiae ) incubation and cation-exchange chromatography (CEC). Both methods allowed complete removal of major soluble carbohydrates (fructose, glucose, galactose, and sucrose), without affecting the content of mulberry bioactives. As an advantage over CEC, the yeast treatment preserves bioactive inositols, and it is an affordable methodology that employs food grade solvents. This work found PLE followed by yeast treatment to be an easily scalable and automatable procedure that can be implemented in the food industry.

The first step in the biosynthesis of cocaine in Erythroxylum coca: the characterization of arginine and ornithine decarboxylases

Despite the long history of cocaine use among humans and its social and economic significance today, little information is available about the biochemical and molecular aspects of cocaine biosynthesis in coca (Erythroxylum coca) in comparison to what is known about the formation of other pharmacologically-important tropane alkaloids in species of the Solanaceae. In this work, we investigated the site of cocaine biosynthesis in E. coca and the nature of the first step. The two principal tropane alkaloids of E. coca, cocaine and cinnamoyl cocaine, were present in highest concentrations in buds and rolled leaves. These are also the organs in which the rate of alkaloid biosynthesis was the highest based on the incorporation of ¹³CO₂. In contrast, tropane alkaloids in the Solanaceae are biosynthesized in the roots and translocated to the leaves. A collection of EST sequences from a cDNA library made from young E. coca leaves was employed to search for genes encoding the first step in tropane alkaloid biosynthesis. Full-length cDNA clones were identified encoding two candidate enzymes, ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), and the enzymatic activities of the corresponding proteins confirmed by heterologous expression in E. coli and complementation of a yeast mutant. The transcript levels of both ODC and ADC genes were highest in buds and rolled leaves and lower in other organs. The levels of both ornithine and arginine themselves showed a similar pattern, so it was not possible to assign a preferential role in cocaine biosynthesis to one of these proteins.

Plant natural products: a primerThe present review is one in the special series of reviews on animal–plant interactions

Over the course of evolution, plants have adapted various structural and chemical mechanisms to protect themselves and interact with their environment. The chemical mechanisms are largely based on the secondary metabolites or natural products. Although plant natural products are generally divided into three main categories (terpenoids, alkaloids, and phenylpropanoids) that are based on structural type and biosynthetic origin, there are many other smaller categories of unique compounds. Many important in planta biological functions can be attributed to plant natural products, in large part, owing to their tremendous structural diversity. To understand the functional roles of plant natural products, both as protective compounds and interorganismal signals, it is important to know how they are formed in plants. This minireview provides a general background about the three main categories of plant natural products, their biosynthetic origins, and their structural diversity.