Beauty of the beast: anticholinergic tropane alkaloids in therapeutics

Exogenous regulation of macronutrients promotes the accumulation of alkaloid yield in anisodus tanguticus (Maxim.) pascher

BACKGROUND

Anisodus tanguticus (Maxim.) Pascher (A. tanguticus) is a valuable botanical for extracting tropane alkaloids, which are widely used in the pharmaceutical industry. Implementing appropriate cultivation methods can improve both the quality and yield of A. tanguticus. A two-year field experiment was conducted from 2021 to 2023 using a single-factor randomized complete block design replicated three times. The study examined the effects of different nutrient levels (nitrogen: 0, 75, 150, 225, 300, 375 kg/ha; phosphorus: 0, 600, 750, 900, 1050, 1200 kg/ha; potassium: 0, 75, 112.5, 150, 187.5, 225 kg/ha) on the growth, primary alkaloid contents, and alkaloid yield of A. tanguticus at different growth stages (S-Greening, S-Growing, S-Wilting; T-Greening, T-Growing, and T-Wilting) in both the roots and aboveground portions.

RESULTS

Our results demonstrate that nutrient levels significantly affect the growth and alkaloid accumulation in A. tanguticus. High nitrogen levels (375 kg/ha) notably increased both root and aboveground biomass, while phosphorus had a minimal effect, especially on aboveground biomass. For alkaloid content (scopolamine, anisodamine, anisodine, atropine), a moderate nitrogen level (225 kg/ha) was most effective, followed by low potassium (75 kg/ha), with phosphorus showing a limited impact. Increased phosphorus levels led to a decrease in scopolamine content. During the T-Growing period, moderate nitrogen addition (225 kg/ha) yielded the highest alkaloid levels per unit area (205.79 kg/ha). In the T-Wilting period, low potassium (75 kg/ha) and low phosphorus (750 kg/ha) resulted in alkaloid levels of 146.91 kg/ha and 142.18 kg/ha, respectively. This indicates nitrogen has the most substantial effect on alkaloid accumulation, followed by potassium and phosphorus. The Douglas production function analysis suggests focusing on root biomass and the accumulation of scopolamine and atropine in roots to maximize alkaloid yield in A. tanguticus cultivation.

CONCLUSIONS

Our findings show that the optimum harvesting period for A. tanguticus is the T-Wilting period, and that the optimal nitrogen addition is 225 kg/ha, the optimal potassium addition is 75 kg/ha, and the optimal phosphorus addition is 600 kg/ha or less.

Human Plasma Butyrylcholinesterase Hydrolyzes Atropine: Kinetic and Molecular Modeling Studies

The participation of butyrylcholinesterase (BChE) in the degradation of atropine has been recurrently addressed for more than 70 years. However, no conclusive answer has been provided for the human enzyme so far. In the present work, a steady-state kinetic analysis performed by spectrophotometry showed that highly purified human plasma BChE tetramer slowly hydrolyzes atropine at pH 7.0 and 25 °C. The affinity of atropine for the enzyme is weak, and the observed kinetic rates versus the atropine concentration was of the first order: the maximum atropine concentration in essays was much less than Km. Thus, the bimolecular rate constant was found to be kcat/Km = 7.7 × 104 M-1 min-1. Rough estimates of catalytic parameters provided slow kcat < 40 min-1 and high Km = 0.3-3.3 mM. Then, using a specific organophosphoryl agent, echothiophate, the time-dependent irreversible inhibition profiles of BChE for hydrolysis of atropine and the standard substrate butyrylthiocholine (BTC) were investigated. This established that both substrates are hydrolyzed at the same site, i.e., S198, as for all substrates of this enzyme. Lastly, molecular docking provided evidence that both atropine isomers bind to the active center of BChE. However, free energy perturbations yielded by the Bennett Acceptance Ratio method suggest that the L-atropine isomer is the most reactive enantiomer. In conclusion, the results provided evidence that plasma BChE slowly hydrolyzes atropine but should have no significant role in its metabolism under current conditions of medical use and even under administration of the highest possible doses of this antimuscarinic drug.

Drug and pro-drug substrates and pseudo-substrates of human butyrylcholinesterase

Butyrylcholinesterase (BChE) is present in plasma and numerous cells and organs. Its physiological function(s) is(are) still unclear. However, this enzyme is of pharmacological and toxicological importance. It displays a broad specificity and is capable of hydrolyzing a wide range of substrates with turnovers differing by several orders of magnitude. Nowaday, these substrates include more than two dozen carboxyl-ester drugs, numerous acetylated prodrugs, and transition state analogues of acetylcholine. In addition, BChE displays a promiscuous hydrolytic activity toward amide bonds of arylacylamides, and slowly hydrolyzes carbamyl- and phosphoryl-esters. Certain pseudo-substrates like carbamates and organophosphates are major drugs of potential medical interest. The existence of a large genetic poly-allelism, affecting the catalytic properties of BChE is at the origin of clinical complications in the use of certain drugs catabolized by BChE. The number of drugs and prodrugs hydrolyzed by BChE is expected to increase in the future. However, very few quantitative data (Km, kcat) are available for most marketed drugs, and except for myorelaxants like succinylcholine and mivacurium, the impact of BChE genetic mutations on catalytic parameters has not been evaluated for most of these drugs.

The patent review of the biological activity of tropane containing compounds

INTRODUCTION

Tropane-derived medications have historically played a substantial role in pharmacotherapy. Both natural and synthetic derivatives of tropane find application in addressing diverse medical conditions. Prominent examples of tropane-based drugs include hyoscine butylbromide, recognized for its antispasmodic properties, atropine, employed as a mydriatic, maraviroc, known for its antiviral effects. trospium chloride, utilized as a spasmolytic for overactive bladder, and ipratropium, a bronchodilator.

AREAS COVERED

We compiled patents pertaining to the biological activity of substances containing tropane up to the year 2023 and categorized them according to the specific type of biological activity they exhibit. ScienceFinder, ScienceDirect, and Patent Guru were used to search for scientific articles and patent literature up to 2023.

EXPERT OPINION

Pharmaceutical researchers in academic and industrial settings have shown considerable interest in tropane derivatives. Despite this, there remains a substantial amount of work to be undertaken. A focused approach is warranted for the exploration and advancement of both natural and synthetic bioactive molecules containing tropane, facilitated through collaborative efforts between academia and industry. Leveraging contemporary techniques and technologies in medicinal and synthetic chemistry, including high throughput screening, drug repurposing,and biotechnological engineering, holds the potential to unveil novel possibilities and accelerate the drug discovery process for innovative tropane-based pharmaceuticals.

Geographically associated endophytic fungi contribute to the tropane alkaloids accumulation of Anisodus tanguticus

Anisodus tanguticus is a valuable plant for extracting tropane alkaloids. However, the mechanisms by which plant microbiome mediate the accumulation of tropane alkaloids in Anisodus tanguticus are still not well understood. In this study, we collected 55 wild Anisodus tanguticus populations on the Tibetan Plateau and the tropane alkaloids content, and root-related bacteria and fungi diversity were analyzed using HPLC and 16 s rDNA and ITS sequencing. The results showed that tropane alkaloids content has obvious geographical distribution characteristics. Anisodine content had a significant positive correlation with latitude, while anisodamine and atropine content had a significant negative correlation with latitude. Variation partition analysis (VPA) showed that root endophytes play a significant role in promoting tropane alkaloid production in Anisodus tanguticus roots. The root endophytes alone explained 14% of the variation, which was the largest contributor. Soil properties variables could independently explain 5% of the variation, and climate variables could explain 1% of the variation. Of these, endophytic fungi alone accounted for 11%, while bacteria explained only 5%. Random forests and Mantel test showed that different regionally enriched endophytic fungi have a greater impact on the accumulation of tropane alkaloids than the whole endophytic fungi. Richness and relative abundance of enriched endophytic fungi in Hengduan-Qilian Mountains (HQ) group has a significant positive correlation with anisodine content, while richness and relative abundance of enriched endophytic fungi in Himalayas-Hengduan Mountains (HH) group has a significant positive correlation with anisodamine and atropine content. And, these enriched endophytic fungi have high network connectivity and distributed in separate network modules. This study further confirmed that endophytes were closely related to tropane alkaloids accumulation in Anisodus tanguticus and contribute to promote sustainable development, cultivation, and precision medicine of Anisodus tanguticus.

Rapid Synthesis of Psychoplastogenic Tropane Alkaloids

Tropane alkaloids are an important class of biologically active small molecules characterized by their 8-azabicyclo[3.2.1]octane core. Because of their numerous medicinal applications, microbial biosynthesis and a variety of chemical syntheses have been designed for individual family members. However, current approaches are not amenable to late-stage structural diversification at N8, C3, C6, or C7, positions that are critical for modulating the biological properties of these molecules. Here, we describe a general approach to the synthesis of tropane alkaloids and their analogues that relies on the construction of the 8-azabicyclo[3.2.1]octane core through aziridination of a cycloheptadiene intermediate, followed by vinyl aziridine rearrangement. Using this strategy, we synthesized six tropane alkaloids and several analogues in only 5-7 steps. Given that the tropane alkaloid scopolamine has been reported to promote structural neuroplasticity and produce antidepressant effects, we tested five tropane-containing compounds for their ability to promote dendritic spine growth in cultured cortical neurons. We found that the orientation of the C3 substituent may play a role in the psychoplastogenic effects of tropane alkaloids. Our work provides a robust platform for producing tropane analogs for future structure-activity relationship studies.

The Evolutionary Pattern of Cocaine and Hyoscyamine Biosynthesis Provides Strategies To Produce Tropane Alkaloids

Cocaine and hyoscyamine are two tropane alkaloids (TA) from Erythroxylaceae and Solanaceae, respectively. These famous compounds possess anticholinergic properties that can be used to treat neuromuscular disorders. While the hyoscyamine biosynthetic pathway has been fully elucidated allowing its de novo synthesis in yeast, the cocaine pathway remained only partially elucidated. Recently, the Huang research group has completed the cocaine biosynthetic route by characterizing its two missing enzymes. This allowed the whole pathway to be transferring into Nicotiana benthamiana to achieve cocaine production. Here, besides highlighting the impact of this discovery, we discuss how TA biosynthesis evolved via the recruitment of two distinct and convergent pathways in Erythroxylaceae and Solanaceae. Finally, while enriching our knowledge on TA biosynthesis, this diversification of the molecular actors involved in cocaine and hyoscyamine biosynthesis opens perspectives in metabolic engineering by exploring enzyme biochemical plasticity that can ease and shorten TA pathway reconstitution in heterologous organisms.

From Plants to Wound Dressing and Transdermal Delivery of Bioactive Compounds

Transdermal delivery devices and wound dressing materials are constantly improved and upgraded with the aim of enhancing their beneficial effects, biocompatibility, biodegradability, and cost effectiveness. Therefore, researchers in the field have shown an increasing interest in using natural compounds as constituents for such systems. Plants, as an important source of so-called "natural products" with an enormous variety and structural diversity that still exceeds the capacity of present-day sciences to define or even discover them, have been part of medicine since ancient times. However, their benefits are just at the beginning of being fully exploited in modern dermal and transdermal delivery systems. Thus, plant-based primary compounds, with or without biological activity, contained in gums and mucilages, traditionally used as gelling and texturing agents in the food industry, are now being explored as valuable and cost-effective natural components in the biomedical field. Their biodegradability, biocompatibility, and non-toxicity compensate for local availability and compositional variations. Also, secondary metabolites, classified based on their chemical structure, are being intensively investigated for their wide pharmacological and toxicological effects. Their impact on medicine is highlighted in detail through the most recent reported studies. Innovative isolation and purification techniques, new drug delivery devices and systems, and advanced evaluation procedures are presented.