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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.

The skeleton of tropane alkaloids is derived from ornithine-derived N -methylpyrrolinium and two malonyl-CoA units. The enzymatic mechanism that connects N -methylpyrrolinium and malonyl-CoA units remains unknown. Here, we report the characterization of three pyrrolidine ketide synthases (PYKS), Aa PYKS, Ds PYKS, and Ab PYKS, from three different hyoscyamine- and scopolamine-producing plants. By examining the crystal structure and biochemical activity of Aa PYKS, we show that the reaction mechanism involves PYKS-mediated malonyl-CoA condensation to generate a 3-oxo-glutaric acid intermediate that can undergo non-enzymatic Mannich-like condensation with N -methylpyrrolinium to yield the racemic 4-(1-methyl-2-pyrrolidinyl)-3-oxobutanoic acid. This study therefore provides a long sought-after biosynthetic mechanism to explain condensation between N -methylpyrrolinium and acetate units and, more importantly, identifies an unusual plant type III polyketide synthase that can only catalyze one round of malonyl-CoA condensation. Tropane alkaloids are medicinally significant plant metabolites generated by an unusual condensation of ornithine-derived and malonyl-CoA precursors. Here, Huang et al. show that pyrrolidine ketide synthase catalyzes a single round of condensation, which is followed by a non-enzymatic Mannich-like condensation.

Plant secondary metabolites play a major role in plant adaptation to stress. Species belonging to Solanaceae family and Datura genus produce tropane alkaloids: D. stramonium, D. tatula and D. innoxia. These species are cultivated for their hyoscyamine (HS) content, whence the interest of this study to induce transformed roots of these species with strain A4 of Agrobacterium rhizogenes. Hairy roots (HRs) of Datura were established at high frequency by infecting vitroplants. All HRs (343 independent lines) were next employed to study the production of HS and growth. A screening of HRs alkaloid content by GC/MS is performed; it reveals, for the first time, the production of 13 alkaloids by the selected root lines. The selection of high productive line offers an interesting option to enhance the productivity. As HS is the dominant compound, the lines of Datura species were selected for their characteristics for biomass and HS production. The elicitors salicylic acid (SA) and acetyl salicylic acid (ASA) were also used to increase HS production. The results showed that the optimal concentration of the two elicitors (AS and ASA) was 0.1 mM. The highest HS content (17.94 +/- 0.14 mg g(-1) D. W.) obtained in HRs of D. tatula treated with 0.1 mM of acetyl salicylic acid.

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.

In this research, tropane alkaloids in Radix physochlainae were extracted by tropine-type ionic liquid (IL) aqueous solutions under ultrasound assistance, and N-propyltropine hexafluorophosphate ([C3Tr][PF6]) was found to be the most ideal IL in this extraction mode after comprehensive screening. When 0.03 mol/L [C3Tr][PF6] aqueous solution was chosen as the extraction solvent, the solid-liquid ratio of raw material powders and ionic liquid aqueous solution was 1:20 (g/mL), ultrasonic power was 90 W and extraction time was 30 min, the extraction efficiency of tropane alkaloids has reached 121.3%. Compared with common heating extraction, it can further shorten the extraction time, improve extraction efficiency and decrease IL consumption. Furthermore, extraction mechanism together with potential toxicity of IL have been explored and discussed.

The rise in cyanobacterial blooms due to eutrophication and climate change has increased cyanotoxin presence in water. Most current water treatment plants do not effectively remove these toxins, posing a potential risk to public health. This study introduces a water treatment approach using nanostructured beads containing magnetic nanoparticles (MNPs) for easy removal from liquid suspension, coated with different adsorbent materials to eliminate cyanotoxins. Thirteen particle types were produced using activated carbon, CMK-3 mesoporous carbon, graphene, chitosan, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidised cellulose nanofibers (TOCNF), esterified pectin, and calcined lignin as an adsorbent component. The particles’ effectiveness for detoxification of microcystin-LR (MC-LR), cylindrospermopsin (CYN), and anatoxin-A (ATX-A) was assessed in an aqueous solution. Two particle compositions presented the best adsorption characteristics for the most common cyanotoxins. In the conditions tested, mesoporous carbon nanostructured particles, P1-CMK3, provide good removal of MC-LR and Merck-activated carbon nanostructured particles, P9-MAC, can remove ATX-A and CYN with high and fair efficacy, respectively. Additionally, in vitro toxicity of water treated with each particle type was evaluated in cultured cell lines, revealing no alteration of viability in human renal, neuronal, hepatic, and intestinal cells. Although further research is needed to fully characterise this new water treatment approach, it appears to be a safe, practical, and effective method for eliminating cyanotoxins from water.

Dopamine transporter (DAT) in the central nervous system is an attractive biomarker for the diagnosis and study of various neurodegenerative diseases. To develop in vivo metabolically stable positron emission tomography (PET) probes for DAT imaging with a high target/background ratio, two F-labeled tropane derivatives with deuteration on both the N-fluoropropyl and 2β-carbomethoxy groups of the tropane scaffold were synthesized and evaluated. Radioligands [ F]6 and [ F]10 were synthesized from anhydroecgonine and radiolabeled with F through a \"two-step one-pot\" method. Lipophilicity, in vitro binding assay and microPET imaging in rats were performed. [ F]10 showed a higher standardized uptake value ratio (SUVr) and was selected for further evaluations by in vivo metabolism and biodistribution. The radioligands [ F]6 and [ F]10 were obtained in radiochemical purities > 98% and molar activity of about 30 GBq/μmol. [ F]6 or [ F]10 demonstrated high specificity and binding affinity to DAT in vitro, with IC values between 2 ~ 3 nM. MicroPET imaging in wild type Sprague-Dawley rats revealed that [ F]10 has a higher SUVr than [ F]6. Blocking experiments demonstrated the selectivity and reversibility of [ F]10 for DAT binding in microPET imaging. The diagnostic efficacy of [ F]10 for DAT-related disorders was verified in semi-PD model rats with microPET. In vivo metabolic studies in rats indicated that [ F]10 exhibited enhanced stability. Biodistribution experiments further confirmed that [ F]10 accumulated in the DAT-rich region of the striatum. [ F]10 is a highly promising metabolically stable F-labeled PET probe for DAT imaging, with potential clinical applications in detecting and monitoring DAT-related neurological disorders.

In this report, we describe a fluorescent assay for the detection of six marine toxins in water. The mechanism of detection is based on a duplex-to-complex structure-switching approach. The six aptamers specific to the targeted cyanotoxins were conjugated to a fluorescent dye, carboxyfluorescein (FAM). In parallel, complementary DNA (cDNA) sequences specific to each aptamer were conjugated to a fluorescence quencher BHQ1. In the absence of the target, an aptamer–cDNA duplex structure is formed, and the fluorescence is quenched. By adding the toxin, the aptamer tends to bind to its target and releases the cDNA. The fluorescence intensity is consequently restored after the formation of the complex aptamer–toxin, where the fluorescence recovery is directly correlated with the analyte concentration. Based on this principle, a highly sensitive detection of the six marine toxins was achieved, with the limits of detection of 0.15, 0.06, 0.075, 0.027, 0.041, and 0.026 nM for microcystin-LR, anatoxin-α, saxitoxin, cylindrospermopsin, okadaic acid, and brevetoxin, respectively. Moreover, each aptameric assay showed a very good selectivity towards the other five marine toxins. Finally, the developed technique was applied for the detection of the six toxins in spiked water samples with excellent recoveries.

Under hypoxic conditions, the expression of Vitreoscilla hemoglobin (VHb) in plants is proposed to increase the productivity of certain oxygen-requiring metabolic pathways by promoting the delivery of oxygen. Tropane alkaloids (TAs) are a class of important plant secondary metabolites with significant medicinal value; the final step in their biosynthesis requires oxygen. Whether heterologous expression of VHb, especially in different subcellular compartments, can accelerate the accumulation of TAs is not known. Herein, the effect of heterologous expression of VHb in different subcellular locations on the TA profile of H . niger hairy roots was investigated. The targeted expression of VHb in the plastids (using p VHb-RecA construct), led to the accumulation of 197.68 μg/g hyoscyamine in the transgenic H . niger hairy roots, which was 1.25-fold of the content present in the lines in which VHb expression was not targeted, and 3.66-fold of that present in the wild type (WT) lines. The content of scopolamine was increased by 2.20- and 4.70-fold in the p VHb-RecA transgenic lines compared to that in the VHb transgenic and WT lines. Our results demonstrate that VHb could stimulate the accumulation of TAs in the transgenic H . niger hairy roots. Quantitative RT-PCR analysis revealed that the expression of key genes involved in TA biosynthesis increased significantly in the VHb transgenic lines. We present the first description of a highly efficient strategy to increase TA content in H . niger . Moreover, our results also shed light on how the production of desired metabolites can be efficiently enhanced by using more accurate and appropriate genetic engineering strategies.

An open-tubular capillary electrochromatography column was prepared by chemically immobilized β-cyclodextrin modified gold nanoparticles onto new surface with the prederivatization of (3-mercaptopropyl)-trimethoxysilane. The synthesized nanoparticles and the prepared column were characterized by transmission electron microscopy, scanning electron microscopy, infrared spectroscopy and ultraviolet visible spectroscopy. When the column was employed as the chiral stationary phase, no enantioselectivity was observed for ten model basic drugs. So β-cyclodextrin was added to the background electrolyte as chiral additive to expect a possible synergistic effect occurring and resulting in a better separation. Fortunately, significant improvement in enantioselectivity was obtained for ten pairs of drug enantiomers. Then, the effects of β-cyclodextrin concentration and background electrolyte pH on the chiral separation were investigated. With the developed separation mode, all the enantiomers (except for venlafaxine) were baseline separated in resolutions of 4.49, 1.68, 1.88, 1.57, 2.52, 2.33, 3.24, 1.63 and 3.90 for zopiclone, chlorphenamine maleate, brompheniramine maleate, dioxopromethazine hydrochloride, carvedilol, homatropine hydrobromide, homatropine methylbromide, venlafaxine, sibutramine hydrochloride and terbutaline sulfate, respectively. Further, the possible separation mechanism involved was discussed.