Neuroprotective Dihydro-β-agarofuran-Type Sesquiterpenes from the Seeds of Euonymus maackii

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Chemically-induced epileptic seizures in zebrafish: A systematic review

The use of zebrafish as a model organism is gaining evidence in the field of epilepsy as it may help to understand the mechanisms underlying epileptic seizures. As zebrafish assays became popular, the heterogeneity between protocols increased, making it hard to choose a standard protocol to conduct research while also impairing the comparison of results between studies. We conducted a systematic review to comprehensively profile the chemically-induced seizure models in zebrafish. Literature searches were performed in PubMed, Scopus, and Web of Science, followed by a two-step screening process based on inclusion/exclusion criteria. Qualitative data were extracted, and a sample of 100 studies was randomly selected for risk of bias assessment. Out of the 1058 studies identified after removing duplicates, 201 met the inclusion criteria. We found that the most common chemoconvulsants used in the reviewed studies were pentylenetetrazole (n = 180), kainic acid (n = 11), and pilocarpine (n = 10), which increase seizure severity in a dose-dependent manner. The main outcomes assessed were seizure scores and locomotion. Significant variability between the protocols was observed for administration route, duration of exposure, and dose/concentration. Of the studies subjected to risk of bias assessment, most were rated as low risk of bias for selective reporting (94%), baseline characteristics of the animals (67%), and blinded outcome assessment (54%). Randomization procedures and incomplete data were rated unclear in 81% and 68% of the studies, respectively. None of the studies reported the sample size calculation. Overall, these findings underscore the need for improved methodological and reporting practices to enhance the reproducibility and reliability of zebrafish models for studying epilepsy. Our study offers a comprehensive overview of the current state of chemically-induced seizure models in zebrafish, highlighting the common chemoconvulsants used and the variability in protocol parameters. This may be particularly valuable to researchers interested in understanding the underlying mechanisms of epileptic seizures and screening potential drug candidates in zebrafish models.

Isolation and Identification of Phytocompounds from Maytenus dhofarensis and Their Biological Potentials

Maytenus dhofarensis Sebsebe (Celestraceae) is a naturally growing shrub in Oman. It is not a reputed medicinal plant in Oman, but it is regionally endemic and causes shivering attacks on goats that graze on it. The chemical investigation of the hexane and chloroform extracts of the fruits and stems of M. dhofarensis afforded dihydro-β-agarofuran-type sesquiterpene pyridine alkaloid (1), lupanyl myristoate (2) and lignanolactone (3). Compounds (1-3) are new isolates from M. dhofarensis. The structures of these compounds were assigned through comprehensive IR, NMR, and ESI-MS analyses, and the relative configurations of compounds 1 and 3 were deduced from density function theory (DFT) calculations and NMR experiments. Compound 1 was assayed against the kinase enzyme and showed no inhibition activity for p38 alpha and delta at a 10 µM test concentration. Compound 3 inhibited the 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) by 69.5%, compared to 70.9% and 78.0% for gallic acid and butylated hydroxyanisole, respectively, which were used as positive controls.

Dihydro-β-agarofuran-type sesquiterpenoids from the seeds of Celastrus virens with lifespan-extending effect on the nematode Caenorhabditis elegans

Twelve dihydro-β-agarofuran-type sesquiterpenoids, including five new ones (1-5), were purified from the seeds of Celastrus virens (Wang et Tang) C. Y. Chent et T. C. Kao. Their chemical structures were characterized via comprehensive spectroscopic analysis, single-crystal X-ray diffraction analysis, and computational prediction of ECD, as well as comparison of observed and reported NMR spectral data. Among the isolates, nine abundant dihydro-β-agarofuran-type sesquiterpenoids were evaluated for their lifespan-extending activity using the nematode Caenorhabditis elegans model. As a result, compounds 1, 2, 5, 6, 8, and 9 (50 μM) significantly extended the mean survival time of C. elegans, respectively, compared with the blank control group (p < 0.05). Further Quantitative RT-PCR showed that the prolonging of lifespan mediated by compounds 1, 6, 8, and 9 were dependent on the transcription factors skn-1 and hsf-1.

Chloroplast Genomic Variation in Euonymus maackii Rupr. and Its Differentiation Time in Euonymus

Euonymus maackii Rupr. is a small deciduous tree belonging to family Celastraceae. It is an important ornamental tree and a potential medicinal plant resource. Here, we assembled and annotated the chloroplast (cp) genome of E. maackii. By combining this genome with seven available cp genomes from Euonymus species, we performed plastome variation analysis of E. maackii and Euonymus. Furthermore, we reconstructed a phylogenetic tree and estimated the differentiation time of E. maackii. The newly assembled cp genome of E. maackii was 157,551 bp in size and had a typical quadripartite structure, which consisted of one large single-copy (LSC 86,524 bp) region, one small single-copy (SSC 18,337 bp) region, and a pair of inverted repeat regions (26,345 bp). A total of 652 single nucleotide polymorphisms (SNPs) and 65 insertions/deletions (indels) were detected between the two cp genomes of E. maackii, with overall genetic variation of 4.1 SNPs per kb or a π value of 0.00443, reflecting a high level of intraspecific variation. Some coding and noncoding regions with higher variation were identified, including trnV-UAC, petN, ycf1-ndhF, trnM-CAU-atpE, rpl2-rpl23, psbZ-trnG-GCC, trnY-GUA-trnE-UUC, trnW-CCA-trnP-UGG, rps16-trnQ-UUG, and psbC-trnS-UGA. The hypervariable coding and noncoding regions in E. maackii were not the same as those in Euonymus. The phylogenetic tree and divergence time based on the whole cp genomes showed that the seven Euonymus species formed a clade, which was sister to that formed with Catha edulis and Maytenus guangxiensis, and they separated 24.74 million years ago. E. maackii and E. hamiltonianus were most closely related, having separated from each other only approximately 2.68 million years ago. Our study provides important genetic information for further studies of E. maackii, such as studies on its phylogeography, population genetics and molecular ecology, and provides new insights into the evolution of the cp genome in Euonymus.

First Report on Inhibitory Effect against Osteoclastogenesis of Dihydro-β-agarofuran-Type Sesquiterpenoids

Dihydro-β-agarofuran-type sesquiterpenoids are characteristic metabolites of Celastraceae plants, and the extracts of these plants have been developed into botanical pesticides. In the course of our efforts to find novel natural biologically active products, eight new dihydro-β-agarofuran-type sesquiterpenoids (1-8) were identified from the stems of Celastrus monospermus Roxb. Their structures were elucidated by extensive spectroscopic analysis, single crystal X-ray crystallography, and electronic circular dichroism (ECD) calculations. In consideration of the efficacy of certain Celastrus plants for the treatment of arthritis and arthralgia in folk medicine, the isolates were evaluated for their inhibitory activities against osteoclastogenesis. As a result, compounds 4, 6, and 7 were found to restrain osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand (RANKL) with IC₅₀ values of 0.58, 1.2, and 6.1 μM, respectively. Furthermore, compound 4 was found to inhibit osteoclastogenesis-related gene (c-Fos, MMP-9, CTSK, TRAP) expression and block c-Fos protein expression and inhibited bone resorption of mature osteoclasts induced by M-CSF and RANKL in a dose dependent manner. This is the first report of dihydro-β-agarofuran-type sesquiterpenoid for their potential medical applications in bone metabolic diseases.

Dihydro-β-agarofuran-Type Sesquiterpenoids from the Seeds of Celastrus virens and Their Multidrug Resistance Reversal Activity against the KB/VCR Cell Line

Twenty-nine dihydro-β-agarofuran-type sesquiterpenoids, including 17 new and 12 known compounds, were obtained from the seeds of Celastrus virens. The structures of the new isolates were characterized by spectroscopic methods and X-ray diffraction analysis. Among these, 20 sesquiterpenoids were evaluated for their multidrug resistance (MDR) reversal activity against the KB/VCR cell line. As a result, compounds 6 and 8 were found to exhibit MDR-reversal activity of more than 10-fold at a concentration of 2 μM, and the reversal fold (RF) ratios of compounds 19, 21, and 24 were >97.9 at a 20 μM nontoxic concentration level.

Synthesis of bilocularin A carbamate derivatives and their evaluation as leucine transport inhibitors in prostate cancer cells

Large-scale extraction of the leaves of the Australian rainforest tree Maytenus bilocularis followed by extensive purification studies afforded the targeted and abundant dihydro-β-agarofuran, bilocularin A, in sufficient quantities (>500 mg) for detailed semi-synthetic chemistry. Eight bilocularin A carbamate analogues were synthesised using a series of commercially available isocyanate reagents in high purity (>95%) and variable yields (9-91%). All previously undescribed analogues were spectroscopically characterised using NMR, UV, IR and MS data. One compound afforded crystalline material and subsequent single crystal X-ray analysis (Cu-Kα) confirmed the chemical structure along with the absolute configuration. All compounds were evaluated for anti-proliferative activity against the human prostate cancer cell line LNCaP; none of the compounds showed significant (>50%) growth inhibition at 20 μM. Compounds were also tested for their ability to inhibit leucine transport in LNCaP cells, and two analogues showed moderate activity with IC₅₀ values of 8.9 and 8.5 μM. This is the first reported synthesis of dihydro-β-agarofuran carbamate derivatives.