Lycodine-type alkaloids from Lycopodiastrum casuarinoides and their acetylcholinesterase inhibitory activity

The Chemistry and Biology of Lycopodium Alkaloids

Lycopodiales, an order comprising 388 distinct species, is the source of Lycopodium alkaloids (LAs), a group of naturally occurring alkaloids that share a common biosynthesis and structural attributes. These remarkable organisms are considered vestiges of ancient ferns, with fossil evidence dating their existence back to an impressive 300 million years. LAs usually are tricyclic or tetracyclic compounds with C16N or C16N2 skeleton. But then there are also have a few C11N, C15N, C15N2, C22N2, and C27N3 skeleton. LAs have attracted much scientific attention because of their important biological activities related to acetylcholinesterase and unique structural characteristics. From 1881 to December 2023, there are 593 LAs from 49 species of Lycopodiales have been reported. Because the total amount of LAs is nearly five times that of 1994, the classification and group allocation of some newly isolated LAs is often challenging and not unambiguous by Ayer's simple classification. This review makes a more systematic and detailed classification for it and provides extensive coverage of naturally occurring LAs discovered from 1881 to December 2023. Until now, there is no comprehensively summary of biological activity of the LAs. This review is the first time covered the biological activity of the all LAs.

Lycocasine A, a Lycopodium Alkaloid from Lycopodiastrum casuarinoides and Its Acid-Sensing Ion Channel 1a Inhibitory Activity

A novel Lycopodium alkaloid, lycocasine A (1), and seven known Lycopodium alkaloids (2-8), were isolated from Lycopodiastrum casuarinoides. Their structures were determined through NMR, HRESIMS, and X-ray diffraction analysis. Compound 1 features an unprecedented 5/6/6 tricyclic skeleton, highlighted by a 5-aza-tricyclic[6,3,1,02,6]dodecane motif. In bioactivity assays, compound 1 demonstrated weak inhibitory activity against acid-sensing ion channel 1a.

Casuattimines A-N, fourteen new Lycopodium alkaloids from Lycopodiastrum casuarinoides with Cav3.1 channel inhibitory activity

Two new dimeric Lycopodium alkaloids, casuattimines A and B (1 and 2), along with twelve previously undescribed Lycopodium alkaloids, casuattimines C-N (3-14), and eight known Lycopodium alkaloids, were isolated from Lycopodiastrum casuarinoides. Casuattimines A and B (1 and 2) are the first two ether-linked Lycopodium alkaloid dimers. Casuattimines C and D (3 and 4) are unique Lycopodium alkaloids characterized by a long fatty acid chain. Structural elucidation was achieved through HRESIMS, NMR, and electronic circular dichroism (ECD) calculations. In addition, the absolute configurations of compounds 7, 13, and 14 were determined by single crystal X-ray diffraction. Compounds 1, 2, and 4 demonstrated notable Cav3.1 channel inhibitory activities presenting IC50 values of 10.75 ± 1.02 μM, 9.33 ± 0.79 μM, and 7.14 ± 0.86 μM, respectively. The dynamics of compound 4 against the Cav3.1 channel and preliminary structure-activity relationships of these active Lycopodium alkaloids were also discussed.

Plant carbonic anhydrase-like enzymes in neuroactive alkaloid biosynthesis

Plants synthesize numerous alkaloids that mimic animal neurotransmitters1. The diversity of alkaloid structures is achieved through the generation and tailoring of unique carbon scaffolds2,3, yet many neuroactive alkaloids belong to a scaffold class for which no biosynthetic route or enzyme catalyst is known. By studying highly coordinated, tissue-specific gene expression in plants that produce neuroactive Lycopodium alkaloids4, we identified an unexpected enzyme class for alkaloid biosynthesis: neofunctionalized α-carbonic anhydrases (CAHs). We show that three CAH-like (CAL) proteins are required in the biosynthetic route to a key precursor of the Lycopodium alkaloids by catalysing a stereospecific Mannich-like condensation and subsequent bicyclic scaffold generation. Also, we describe a series of scaffold tailoring steps that generate the optimized acetylcholinesterase inhibition activity of huperzine A5. Our findings suggest a broader involvement of CAH-like enzymes in specialized metabolism and demonstrate how successive scaffold tailoring can drive potency against a neurological protein target.

Lycopodiastrum casuarinoides: An overview of their phytochemicals, biological activities, structure-activity relationship, biosynthetic pathway and 13C NMR data

Huperzine A, a lycodine-type alkaloid, exhibits potent inhibitory activity against acetylcholinesterase (AChE) and has been utilized to treat neurodegenerative diseases' symptoms. Lycopodiastrum casuarinoides, a member of the family Lycopodiaceae, is renowned for its lycodine-type alkaloids. Some of these alkaloids show various pharmacological benefits, such as anti-cholinesterase, neuroprotective, and cytotoxic effects. To date, 113 chemical compounds, including seventy-four lycodine-type alkaloids, ten terpenoids, eleven aliphatics, and eighteen other compounds, have been isolated from this plant. In this review, we have discussed phytochemicals and biological activities of the reported compounds of L. casuarinoides. Moreover, structure-activity relationship (SAR), plausible biosynthetic pathways, and ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) data of the lycodine-type alkaloids are also summarized.

Molecular docking and molecular dynamics approach to identify potential compounds in Huperzia squarrosa for treating Alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is a lingering progressive neurodegenerative disorder that causes patients to lose cognitive function. The enzyme Acetylcholinesterase (AChE), Butyrylcholinesterase (BuChE), Monoamine oxidase A (MAO A), Beta-secretase cleavage enzyme (BACE 1) and N-methyl-D-aspartate (NMDA) receptors play an important role in the pathogenesis of Alzheimer's disease. Therefore, inhibiting enzymes is an effective method to treat Alzheimer disease. In this study, we evaluated in silico inhibitory effects of AChE, BuChE, MAO A, BACE 1 and NMDA enzyme of Huperzia squarrosa's compounds.

METHODS

The three-dimensional (3D) of N-methyl-D-aspartate receptor (PDB ID: 1PBQ), enzyme β-secretase 1 (PDB ID: 4X7I), enzyme monoamine oxidase A (PDB ID: 2Z5X), enzyme butyrylcholinesterase (PDB ID: 4BDS) and enzyme acetylcholinesterase (PDB ID: 1EVE) were retrieved from the Protein Data Bank RCSB. Molecular docking was done by Autodock vina software and molecular dynamics (MD) simulation of the ligand-protein complex with the least binding energy pose was perfomed by MOE. Lipinski Rule of Five is used to compare compounds with drug-like and non-drug-like properties. Pharmacokinetic parameters of potential compounds were evaluated using the pkCSM tool.

RESULTS

Based on previous publication of Huperzia squarrosa, we have collected 15 compounds. In these compounds, huperzine B, huperzinine, lycoposerramine U N-oxide, 12-epilycodine N-oxide showed strongly inhibit the five AChE, BuChE, MAO A, BACE 1 and NMDA targets for Alzheimer's treatment. Lipinski rule of five and ADMET predict have shown that four above compounds have drug-likeness properties, good absorption ability and cross the blood-brain barrier, which have the most potential to become drugs for the treatment of Alzheimer's in the future. Furthermore, MD study showed that huperzine B and huperzinine have stability of the docking pose with NMDA target.

CONCLUSIONS

In this study, we found two natural compounds in Huperzia squarrosa including Huperzine B and Huperzinine have drug-likeness properties, good absorption ability and cross the blood-brain barrier, which have potential to become drugs for the treatment of Alzheimer's in the future.

Dose Dependent Effects of Breynia cernua Against the Paraquat Induced Parkinsonism like Symptoms in Animals' Model: In Vitro, In Vivo and Mechanistic Studies

The aims and objectives of the study were to evaluate the antiParkinson's (PD) potential of B cernua (BCE). B cernua (Poir.) Müll. Arg. (B cernua) is a member of the Phyllanthaceae family. HPLC revealed the presence of various phytochemicals. Study was conducted for 40 days. After PD induction by paraquat behavioural studies were carried out. Biochemical parameters such as DPPH, NO-scavenging, Ferrous reducing power, MDA, GSH, CAT, SOD, acetylcholinesterase (AChE), neurotransmitter estimation and TNF-α and IL-6 levels were determined. DPPH, NO-scavenging and Ferrous reducing power assays showed 78.02%, 48.05% and 71.45% inhibitions, respectively. There was significant improvement in motor functions and coordination in a dose-dependent manner (50 < 250 < 500 mg/kg) in PD rat model. Biochemical markers; SOD, CAT, GPx and GSH showed significant restoration (P < .001) while MDA showed significant decrease (P < .05). The AChE level was significantly reduced (P < .05) at 500 mg/kg while neurotransmitters were significantly improved (P < .001) in a dose-dependent fashion. The ELISA results showed significant (P < .001) down-regulation of IL-6 and TNF-α level. In conclusion, it is suggested that BCE has the potential to reduce the symptoms of PD.

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.

Recently isolated lycodine-type Lycopodium alkaloids and their total synthesis: a review

Background

Since long back, several plants species belonging to family Lycopodiaceae or Huperziaceae are being traditionally used in treatment of diseases like Alzheimer’s disease and myasthenia gravis. In 1986, huperzine A, structurally lycodine type of alkaloid was isolated and established as potent acetylcholine esterase inhibitor. Hence, further, in pursuit of similar compounds, several hundreds of different types of lycopodium alkaloids have been isolated from different Lycopodiaceae or Huperziaceae plants species.

Main body

For few of these recently isolated alkaloids, the possible mechanisms of their biosynthesis have been proposed while few of them were tried for their laboratory total asymmetric synthesis. This review summarized lycodine-type Lycopodium alkaloids, whose isolation, biosynthesis, and total synthesis have been reported after 2000. It also includes structure–activity relationship.

Short conclusion

More than 40 lycodine-type alkaloids have been isolated and structurally elucidated since 2000. Their biosynthetic pathway suggested that they got biosynthesized from lysine, while structure–activity relationship established the structural requirement of lycodine-type alkaloids to possess potent acetylcholine esterase inhibitory activity.

Mining lycodine-type alkaloid biosynthetic genes and genetic markers from transcriptome of Lycopodiastrum casuarinoides

Objective

Lycopodiastrum casuarinoides, a fern of the Lycopodiaceae family, is a traditional Chinese medicine, which has similar efficacy to that of Huperzia serrata in treating rheumatoid arthritis (RA). However, they are different in the contents and compositions of lycopodium alkaloids. In this study, the biosynthesis related genes of lycopodium alkaloids and genetic markers are discovered in L. casuarinoides transcriptome.

Methods

The plant of L. casuarinoides was collected and was subjected to the RNA isolation, cDNA library construction, high throughput RNA sequencing and bioinformatics analysis.

Results

Totally 124, 524 high-quality unigenes were assembled from RNA sequencing reads, with an average sequence length of 601 bp. Among the L. casuarinoides transcripts, 61,304 shared the significant similarity (E-value < 10⁻⁵) with existing protein sequences in the public databases. From 124,524 unigenes, 47,538 open reading frames (ORFs) were predicted. Based on the bioinformatics analysis, all possible enzyme genes involved in the lycodine-type alkaloids biosynthetic pathway of L. casuarinoides were identified, including lysine decarboxylase (LDC), primary amine oxidase (PAO), malonyl-CoA decarboxylase, etc. Sixty-four putative cytochrome p450 (CYP) and 827 putative transcription factors were selected from the transcriptome unigenes as the candidates of lycodine-type alkaloids biosynthesis modifiers. Furthermore, 13,352 simple sequence repeats (SSRs) were identified from 124,524 unigenes, of which dinucleotide motifs AG/CT were the most abundant (50.1%). Meanwhile, we confirmed the amplification effectiveness of 25 PCR primer pairs for randomly selected SSRs.

Conclusion

We obtained the comprehensive transcriptomic information from the high throughput RNA sequencing and bioinformatics analysis, which provided a valuable resource of transcript sequences of L. casuarinoides in public databases.

Biotransformation of Huperzine B by a Fungal Endophyte of Huperzia serrata

The biotransformation of huperzine B (hupB), one of the characteristic bioactive constituents of the medicinal plant Huperzia serrata, by a fungal endophyte of the host plant was studied. One new compound, 8α,15α-epoxyhuperzine B (1), along with two known oxygenated hupB analogs, 16-hydroxyhuperzine B (2) and carinatumin B (3), was isolated and identified. The structures of all the isolates were deduced by spectroscopic methods including NMR, MS, IR, and UV spectra. The known compounds 2 and 3 were obtained from a microbial source for the first time. To the best of our knowledge, it is the first report on the microbial transformation of hupB and would facilitate further structural modification of hupB by chemo-enzymatic method. In the LPS-induced neuro-inflammation injury assay, 8α,15α-epoxyhuperzine B (1) exhibited moderate neuroprotective activity by increasing the viability of U251 cell lines with an EC₅₀ of 40.1 nm.

Lycofargesiines A-F, further Lycopodium alkaloids from the club moss Huperzia fargesii

Six undescribed Lycopodium alkaloids (LAs) comprising four lycodine-type (lycofargesiines A-D), one lycopodine-type (lycofargesiine E), and a phlegmarine-type (lycofargesiine F), together with 16 known ones were isolated from the club moss Huperzia fargesii. Their structures and absolute configurations were determined by extensive spectroscopic methods, electronic circular dichroism (ECD) analysis, and density functional theory (DFT) calculations. (7S,8R,12R,13R)-Lycofargesiine A is a rare naturally occurring LA possessing an exocyclic double bond between C-15 and C-16, with ring A being a rare 2,3-dihyropyridone motif. Lycofargesiine D is an uncommon lycodine-type alkaloid featuring a unique N-acetylated tetrahydropyridinyl segment (ring A), whereas lycofargesiine F is the first phlegmarane-type LA bearing two nitrone moieties. In addition to the isolated huperzine A in this study, another two isolates (lycofargesiine C and 16-hydroxyhuperzine A) were also found to show inhibitory activities against acetylcholinesterase (AChE), with IC₅₀ values of 8.63 and 5.18 μM, respectively.

Lycodine-type alkaloids and their glycosides from Lycopodiastrum casuarinoides

Thirteen previously undescribed lycodine-type Lycopodium alkaloids, namely, five alkaloids (lycocasuarines D-H) each possessing an uncommon five-membered C ring and eight Lycopodium alkaloid glycosides (casuarinosides A-H), together with a known analog, were isolated from the aerial parts of Lycopodiastrum casuarinoides (Spring) Holub ex R.D.Dixit (Lycopodiaceae). The structures of the compounds were elucidated by extensive spectroscopic analysis, single-crystal X-ray diffraction, and chemical methods. In addition, the acetylcholinesterase inhibitory activity of the isolated compounds was evaluated.

Lycodine-Type Lycopodium Alkaloids from the Whole Plants of Huperzia serrata

Three new lycodine-type Lycopodium alkaloids, namely 1-methyllycodine (1), 8α-hydroxy-15,16-dehydro-des-N-methyl-α-obscurine (2), N-methyl-16-hydroxyhuperzine B (3), and one new natural lycodine-type Lycopodium alkaloid, N-methylhuperzine A (4), along with 11 known analogues (5-15), were isolated from the whole plants of club moss Huperzia serrata. The structures of 1-4 were elucidated on the basis of NMR spectroscopic and mass spectrometry data. Among them, compound 1 was the first lycodine-type alkaloid possessing a methyl group at C-1. In addition, the structure of 5 was confirmed by the single-crystal X-ray crystallography data and its ¹³C NMR was reported for the first time in current study. Compounds 1-5 were tested their BACE1 inhibitory activity.

Obscurumines H-P, new Lycopodium alkaloids from the club moss Lycopodium obscurum

Seven new fawcettimine-type (1-7) and two new lycopodine-type (8 and 9) Lycopodium alkaloids, as well as 10 known compounds, were isolated from the club moss, Lycopodium obscurum L. The structures of obscurumines H-P (1-9) were determined based on high-resolution MS and 1D and 2D NMR data. Compounds 1 and 2 include a new skeleton that is formed via the linkage of C-9-N-2', which is rarely present in Lycopodium alkaloids. The in vitro acetylcholinesterase (AChE) inhibitory activity assay showed that 5 exhibited weak anti-AChE activity with an IC50 value of 81.0 μM. Compound 8 exhibited inhibition of the secretion of IL-2 in phytohemagglutinin (PHA) and phorbol myristate acetate (PMA) stimulated Jurkat cells, and the IC50 value was 17.2 μM.

Ervatamines A-I, Anti-inflammatory Monoterpenoid Indole Alkaloids with Diverse Skeletons from Ervatamia hainanensis

Nine new monoterpenoid indole alkaloids, ervatamines A-I (1-9), and five known ones (10-14), were isolated from Ervatamia hainanensis. The new structures were elucidated by extensive spectroscopic analysis and comparison to known compounds. Their absolute configurations were determined by various methods including computational methods, X-ray diffraction analysis, and electronic circular dichroism spectroscopy, as well as chemical transformations. Ervatamine A (1) is a ring-C-contracted ibogan-type monoterpenoid indole alkaloid with an unusual 6/5/6/6/6 pentacyclic rearranged ring system. Ervatamines B-E (2-5) display a nitrogen-containing 9/6 ring system, which is rarely observed in nature. The epimeric ervatamines B (2) and C (3) possess a 22-nor-monoterpenoid indole alkaloid carbon skeleton, which was only found in deformylstemmadenine. Compounds 10 and 14 exhibited significant anti-inflammatory activities, with IC50 values of 25.5 and 41.5 μM, respectively, while the IC50 value of indomethacin as a positive control was found to be 42.6 μM. Additionally, compound 9 showed mild activity against 786-O and HL-60 cell lines.

Acetylcholinesterase and carbonic anhydrase isoenzymes I and II inhibition profiles of taxifolin

Taxifolin, also known as dihydroquercetin, is a flavonoid commonly found in plants. Carbonic anhydrase (CA, EC 4.2.1.1) plays an important role in many critical physiological events including carbon dioxide (CO2)/bicarbonate (HCO3(-)) respiration and pH regulation. There are 16 known CA isoforms in humans, of which human hCA isoenzymes I and II (hCA I and II) are ubiquitous cytosolic isoforms. In this study, the inhibition properties of taxifolin against the slow cytosolic isoenzyme hCA I, and the ubiquitous and dominant rapid cytosolic isoenzyme hCA II were studied. Taxifolin, as a naturally bioactive flavonoid, has a K(i) of 29.2 nM against hCA I, and 24.2 nM against hCA II. For acetylcholinesterase enzyme (AChE) inhibition, K(i) parameter of taxifolin was determined to be 16.7 nM. These results clearly show that taxifolin inhibited both CA isoenzymes and AChE at the nM levels.