Hyoscyamine-6β-hydroxylase (H6H, EC 1.14.11.11) is a plant enzyme that catalyses the last two steps in the biosynthesis of the anticholinergic drug scopolamine, i.e. the hydroxylation of hyoscyamine to 6β-hydroxyhyoscyamine (anisodamine) and subsequent oxidative ring-closure to the 6,7-β-epoxide. A H6H gene homologue was isolated from the plant Brugmansia sanguinea (BsH6H) and recombinantly cloned into Escherichia coli, expressed and purified using an effective SUMO-fusion procedure. Enzymatic activity is approximately 40-fold higher for the first reaction step and the substrate affinity is comparable to other characterized H6H homologues (Km ∼ 60 μM). Truncation of an H6H enzyme flexible N-terminal region yields an active and stable yet more compact enzyme version.

No information is available on the use of atropine during breastfeeding. Long-term use of atropine might reduce milk production or milk letdown, but a single systemic or ophthalmic dose is not likely to interfere with breastfeeding. During long-term use, observe for signs of decreased lactation (e.g., insatiety, poor weight gain).

Hyoscyamine 6β-hydroxylase (H6H) is an α-ketoglutarate dependent mononuclear nonheme iron enzyme that catalyzes C6-hydroxylation of hyoscyamine and oxidative cyclization of the resulting product to give the oxirane natural product scopolamine. Herein, the chemistry of H6H is investigated using hyoscyamine derivatives with modifications at the C6 or C7 position as well as substrate analogues possessing a 9-azabicyclo[3.3.1]nonane core. Results indicate that hydroxyl rebound is unlikely to take place during the cyclization reaction and that the hydroxylase versus oxidative cyclase activity of H6H is correlated with the presence of an exo-hydroxy group having syn-periplanar geometry with respect to the adjacent H atom to be abstracted.

Penehyclidine hydrochloride (PHC), a type of hyoscyamus drug, has both antimuscarinic and antinicotinic activities and retains potent central and peripheral anticholinergic activities. Compared with other hyoscyamine, the notable advantage of PHC is that it has few M2 receptor-associated cardiovascular side effects. Recent studies and clinical trials have suggested that treatment with penehyclidine hydrochloride may also possess good effects in the treatment of lung injury. The mechanism responsible for this effect has yet to be determined; however, one possibility is that they might do so by a direct effect on pulmonary vascular endothelium. Since inflammatory reactions of the endothelium are signs of endothelial injury in the pathogenesis of lung injury, we determined the effects of penehyclidine hydrochloride on endothelial inflammatory injury in cultured human pulmonary microvascular endothelial cells (HPMVEC). Furthermore, human pulmonary microvascular endothelial cells were transfected with a shRNA-containing plasmid that specifically targets beta-arrestin-1 mRNA, to test whether the effect of penehyclidine hydrochloride on lipopolysaccharide (LPS)-induced endothelial cell injury is dependent on its upregulation of beta-arrestin-1 or not. Penehyclidine hydrochloride reduced the inflammatory responses to LPS stimulation, as evidenced by reduced lactate dehydrogenase (LDH), tumor necrosis factor-alpha (TNF-α), and interleukelin-6 (IL-6) levels, as well as vascular cell adhesion molecule 1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1) expressions. This was found to result from increased beta-arrestin-1 expression and decreased nuclear transcription factor-κB (NF-κB) activation. Expression of a shRNA-containing plasmid that specifically targets beta-arrestin-1 mRNA nullified these effects of penehyclidine hydrochloride. The results indicate that penehyclidine hydrochloride exerts a protective effect on pulmonary microvascular endothelial inflammatory injury induced by LPS. We also demonstrate that this is due to its ability to increase beta-arrestin-1, which in turn inhibits NF-κB activation.

In order to study the mechanism of nitrogen metabolism and secondary metabolism in Atropa belladonna hairy roots treated with yeast extract, yeast extract（YE） was added to the culture medium. Then the changes of physiological and biochemical indexes of A. belladonna hairy roots after treatment with YE were detected. The results are as follows，the activity of key enzymes of nitrogen metabolism changed differently. Compared with the control group (CK), the activity of nitrate reductase (NR) and glutamine synthetase (GS) were significantly increased, while the activity of glutamate dehydrogenase (GDH) was not changed significantly. The content of nitrate nitrogen, ammonium nitrogen had a significant decrease,but the content of soluble protein, free amino acid, total nitrogen are significantly more than CK. Moreover, YE treatment led to the increase of the content precursor amino acids (ornithine and arginine) and precursor putrescine in secondary metabolic pathways of A. belladonna. The expression level of gene putrescine N-methyl transferase (pmt), tropinone reductase-I (trI) and hyoscyamine 6-β-hydroxylase(h6h) all increased in a different rate caused by YE treatment, which eventually led to the increase of the yield of tropane alkaloids. The yield of hyoscyamine and scopolamine were 3.09 and 1.85 folds than that of CK after 16 days treatment time. The results indicated that YE can induce more synthesis of tropane alkaloids by increasing the activity of key enzymes in nitrogen metabolism to provide more synthetic materials for secondary metabolism, meanwhile it regulated the expression level of some genes of key metabolic enzyme to accelerate secondary metabolism.

Atropa belladonna, commonly known as belladonna or deadly nightshade, ranks among one of the most poisonous plants in Europe and other parts of the world. The plant contains tropane alkaloids including atropine, scopolamine, and hyoscyamine, which are used as anticholinergics in Food and Drug Administration (FDA) approved drugs and homeopathic remedies. These alkaloids can be very toxic at high dose. The FDA has recently reported that Hyland's baby teething tablets contain inconsistent amounts of Atropa belladonna that may have adverse effects on the nervous system and cause death in children, thus recalled the product in 2017. A greater understanding of the neurotoxicity of Atropa belladonna and its modification of genetic polymorphisms in the nervous system is critical in order to develop better treatment strategies, therapies, regulations, education of at-risk populations, and a more cohesive paradigm for future research. This review offers an integrated view of the homeopathy and neurotoxicity of Atropa belladonna in children, adults, and animal models as well as its implications to neurological disorders. Particular attention is dedicated to the pharmaco/toxicodynamics, pharmaco/toxicokinetics, pathophysiology, epidemiological cases, and animal studies associated with the effects of Atropa belladonna on the nervous system. Additionally, we discuss the influence of active tropane alkaloids in Atropa belladonna and other similar plants on FDA-approved therapeutic drugs for treatment of neurological disorders.

This work reported a new method of design for the immobilization of acetylcholinesterase (AChE) based on its molecular structure to improve its sensitivity and stability. The immobilization binding site on the surface of AChE was determined using MOLCAD's multi-channel functionality. Then, 11 molecules ((+)-catechin, (-)-epicatechin, (-)-gallocatechin, hesperetin, naringenin, quercetin, taxifolin, (-)-epicatechin gallate, flupirtine, atropine, and hyoscyamine) were selected from the ZINC database (about 50 000 molecules) as candidate affinity ligands for AChE. The fluorescence results showed that the binding constant Kb between AChE and the ligands ranged from 0.01344 × 104 to 4.689 × 104 M-1 and there was one independent class of binding site for the ligands on AChE. The AChE-ligand binding free energy ranged from -12.14 to -26.65 kJ mol-1. Naringenin, hesperetin, and quercetin were the three most potent immobilized affinity ligands. In addition, it was confirmed that the binding between the immobilized ligands only occurred at a single site, located in an inactive area on the surface of AChE, and did not affect the enzymatic activity as shown through a competition experiment and enzyme assay. This method based on protein surface structural recognition with high sensitivity and stability can be used as a generic approach for design of the enzyme immobilization and biosensor development.

Hyoscyamine and scopolamine are two main alkaloids in Atropa belladonna with great medicinal value. In this paper, the contents of hyoscyamine and scopolamine, the upstream products in alkaloid synthesis, and the expression levels of key enzyme genes PMT, TRⅠ and H6H in secondary metabolism of A. belladonna seedlings were measured to clarify the mechanism of nitrogen forms regulating alkaloids synthesis.The results showed that the 50/50 (NH⁺₄/NO⁻₃) treatment was more favorable for the accumulation of alkaloids and the conversion of hyoscyamine to scopolamine. The content of putrescine was almost consistent with the change of key enzymes activities in the synthesis of putrescine, they both increased with the rise of ammonium ratio, reaching the highest at 75/25 (NH⁺₄/NO⁻₃). The detection of signaling molecule nitric oxide (NO) showed that the NO concentration decreased with the decrease of nitrate proportion. Further detection of gene expression levels of PMT, TRⅠ and H6H in TAs synthesis pathway showed that a certain amount of ammonium promoted the expression of PMT and H6H in roots. When the ratio of ammonium to nitrate was 50/50, PMT, TRⅠ and H6H in leaves and roots had higher expression levels. It can be speculated that the regulation of the formation of hyoscyamine to scopolamine by nitrogen forms mainly through affecting the expression of key enzyme genes. 50/50 (NH⁺₄/NO⁻₃) treatment increased the gene expression of TRⅠ in both leaves and roots as well as PMT and H6H in roots, promoting the synthesis of putrescine to hyoscyamine and the conversion of hyoscyamine to scopolamine.

N-methylputrescine is the precursor of nicotine and pharmaceutical tropane alkaloids such as hyoscyamine. Putrescine N-methyltransferase (PMT) catalyzes the N-methylation of putrescine to form N-methylputrescine. While the role of PMT in nicotine biosynthesis is clear, knowledge of PMT in the biosynthesis of tropane alkaloids (TAs) and the regulation of polyamines remains limited. We characterized a PMT gene from Hyoscyamus niger, designated HnPMT that was specifically expressed in roots, especially in the secondary roots and dramatically induced by methyl jasmonate (MeJA). The GUS gene was specifically expressed in Arabidopsis roots or in the vascular tissues, including pericycles and endodermis, of the H. niger hairy root cultures, when it was driven by the 5'-flanking promoter region of HnPMT. The recombinant HnPMT was purified for enzymatic assays. HnPMT converted putrescine to form N-methylputrescine, as confirmed by LC-MS. The kinetics analysis revealed that HnPMT had high affinity with putrescine but low catalytic activity, suggesting that it was a rate-limiting enzyme. When HnPMT was suppressed in the H. niger plants by using the VIGS approach, the contents of N-methylputrescine and hyoscyamine were markedly decreased, but the contents of putrescine, spermidine and a mixture of spermine and thermospermine were significantly increased; this suggested that HnPMT was involved in the biosynthesis of tropane alkaloids and played a competent role in regulating the biosynthesis of polyamines. Functional identification of HnPMT facilitated the understanding of TA biosynthesis and thus implied that the HnPMT-catalyzed step might be a target for metabolic engineering of the TA production in H. niger.