Australindolones, New Aminopyrimidine Substituted Indolone Alkaloids from an Antarctic Tunicate Synoicum sp.

Five new alkaloids have been isolated from the lipophilic extract of the Antarctic tunicate Synoicum sp. Deep-sea specimens of Synoicum sp. were collected during a 2011 cruise of the R/V Nathanial B. Palmer to the southern Scotia Arc, Antarctica. Crude extracts from the invertebrates obtained during the cruise were screened in a zebrafish-based phenotypic assay. The Synoicum sp. extract induced embryonic dysmorphology characterized by axis truncation, leading to the isolation of aminopyrimidine substituted indolone (1-4) and indole (5-12) alkaloids. While the primary bioactivity tracked with previously reported meridianins A-G (5-11), further investigation resulted in the isolation and characterization of australindolones A-D (1-4) and the previously unreported meridianin H (12).

Toxicity assessment of gelsenicine and the search for effective antidotes.

BACKGROUND: Gelsenicine, one of the most toxic alkaloids of Gelsemium elegans Benth (G. elegans), causes severe respiratory depression. However, its toxicity mechanisms are yet to be elucidated and no effective antidotes are available. OBJECTIVE: This study aimed to analyse the toxicity characteristics of gelsenicine. METHODS: Both acute and sub-acute toxicities were evaluated. Gelsenicine distribution and elimination in the central nervous system (CNS) and blood were observed. Effective antidotes for gelsenicine poisoning were screened. RESULTS: In the acute toxicity study, gelsenicine was highly toxic, and female rats exhibited greater sensitivity to gelsenicine than male rats (LD50 0.520 mg/kg vs 0.996 mg/kg, respectively). Death was primarily caused by respiratory failure. However, in the sub-acute toxicity study, no significant organ damage was observed. Gelsenicine was easily absorbed from the gastrointestinal tract and penetrated the blood-brain barrier, reaching peak concentrations in the CNS within 15 min and rapidly decreasing thereafter. Flumazenil or diazepam combined with epinephrine reversed gelsenicine toxicity and significantly improved survival rate in mice. CONCLUSIONS: Gelsenicine is a highly toxic substance that affects nerve conduction without causing damage; the potential toxic mechanism is possibly associated with GABAA receptors. Our findings provide insights into the clinical treatment of gelsenicine-related poisoning and its toxicity mechanisms.

Toxicokinetics, in vivo metabolic profiling, and in vitro metabolism of gelsenicine in rats.

Gelsenicine, mainly isolated from Gelsemium elegans Benth., is one of the most toxic alkaloids. The lack of information on gelsenicine leads to inaccurate risk and poisoning evaluation. In this study, the metabolic profiling and toxicokinetics of gelsenicine was studied by ultra-high performance liquid chromatography (UPLC) with quadrupole time-of-flight (Q-ToF) and tandem mass spectrometry in rats after intraperitoneal (i.p., 40 µg/kg) and intragastric (i.g., 60 µg/kg) administration. After i.p. administration, the area under the curve (AUC), the apparent volume of distribution (V), and the total body clearance (CL/F) of gelsenicine in plasma were 3.79 µg/L h, 38.47 L/kg, and 11.87 mL/h kg, respectively. After i.g. administration, the corresponding values were slightly increased (5.49 µg/L h; 53.10 mL/kg, and 12.66 mL/h kg). The toxicokinetic results indicated that the hepatic first-pass effect was predominant after i.p. administration. The UPLC-Q-ToF-MS data revealed nine metabolites in plasma, urine, and bile which were largely obtained by demethylation, hydroxylation, acetylation and glycine conjugation. Metabolites were mainly excreted through urine and bile, most of which in urine was basically eliminated in 24 h. Molecular docking and liver microsome experiments further showed that gelsenicine was metabolized by cytochrome P450 3A4 and 3A5. Summarizing, the present study provides metabolic and toxicokinetic information on gelsenicine which in turn may help in future risk assessment and forensic identification after poisonings.

Phosphoproteomics reveals NMDA receptor-mediated excitotoxicity as a key signaling pathway in the toxicity of gelsenicine.

Gelsenicine is one of the most toxic compounds in the genus Gelsemium, but the mechanism of toxicity is not clear. In this paper, tandem mass tag quantitative phosphoproteomics was used to study the changes in protein phosphorylation in different brain regions at different time points after gelsenicine poisoning in mice. The correlation between neurotransmitter receptors and the toxicity of gelsenicine was analyzed by molecular docking and rescue experiments. Parallel reaction monitoring (PRM) was used to verify the related proteins. A total of 17877 unique phosphosites were quantified and mapped to 4170 brain proteins to understand the signaling pathways. Phosphoproteomics revealed gelsenicine poisoning mainly affected protein phosphorylation levels in the hippocampus, and through bioinformatics analysis, it was found gelsenicine poisoning significantly affected neurotransmitter synaptic pathway. The molecular docking results showed that gelsenicine could bind to the N-methyl-D-aspartic acid receptor (NMDAR). In addition, we found that NMDA was effective in improving the survival rate of the animals tested, and this effect was associated with reduced protein phosphorylation by PRM validation. The results revealed that gelsenicine affects neurotransmitter release and receptor function. This is the first demonstration that NMDA receptor-mediated excitotoxicity is a key signaling pathway in the toxicity of gelsenicine.

Investigation on the binding of cyanobacterial metabolite calothrixin A with human serum albumin for evaluating its potential toxicology.

Calothrixin A (CLA), as a carbazole-1,4-quinone alkaloid with unique indolo [3,2-j] phenanthridine framework, is a natural metabolite from the Calothrix cyanobacteria. Since the interaction to the functional serum albumins may play an important role in estimating its potential physiological or toxicological effects in vivo, we here explored the binding information of CLA with human serum albumin (HSA) by multi-spectroscopic experiments and computational approaches. The molecular docking results showed that there was one binding site of CLA to the site I (subdomain IIA) of HSA, causing the spontaneous formation of the ground state complex of CLA-HSA through the integration of hydrogen bond, hydrophobic interaction, and electrostatic interaction. Moreover, CLA could effectively trigger the change of HSA's secondary structure because of an obvious decrease of α-helical content in HSA. Taking into consideration of the crucial role of HSA to transport extraneous functional small molecules in vivo, this study may provide a worthy theoretical basis to evaluate the in vivo toxicity of CLA, aiming to reduce/avoid the potential toxic side effects of CLA in the next hit-to-lead campaign.

Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy.

Vacuolar myelinopathy is a fatal neurological disease that was initially discovered during a mysterious mass mortality of bald eagles in Arkansas in the United States. The cause of this wildlife disease has eluded scientists for decades while its occurrence has continued to spread throughout freshwater reservoirs in the southeastern United States. Recent studies have demonstrated that vacuolar myelinopathy is induced by consumption of the epiphytic cyanobacterial species Aetokthonos hydrillicola growing on aquatic vegetation, primarily the invasive Hydrilla verticillata Here, we describe the identification, biosynthetic gene cluster, and biological activity of aetokthonotoxin, a pentabrominated biindole alkaloid that is produced by the cyanobacterium A. hydrillicola We identify this cyanobacterial neurotoxin as the causal agent of vacuolar myelinopathy and discuss environmental factors-especially bromide availability-that promote toxin production.

Bioactivity and cytotoxicity profiling of vincosamide and strictosamide, anthelmintic epimers from Sarcocephalus latifolius (Smith) Bruce leaf.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaf of Sarcocephalus latifolius is known to be used traditionally by the Fulanis in Nigeria to deworm animals. As helminthosis remains a major constraint to profitable livestock production worldwide, a precarious situation aggravated by the advent of resistant parasites, the discovery of new anthelmintics is a priority, necessitating exploration of medicinal plants for their anthelmintic principles. AIM OF THE STUDY: To identify and characterise compounds with anthelmintic activity from the leaf of Sarcocephalus latifolius. MATERIALS AND METHODS: Powdered S. latifolius leaves were extracted by successive maceration with n-hexane, chloroform and acetone. The dried extracts were evaluated for anthelmintic activity against Haemonchus placei adult worms, and the most active extract was subjected to bioassay-guided chromatographic separations. The isolated compounds were evaluated for cytotoxicity against the mammalian HeLa and MC3T3-E1 cell lines, using alamar blue and CellTitreGloTM to quantify cell viability. LC50 values were computed from the in vitro anthelmintic activity data by fitting to a non-linear regression equation (variable slope). Isolated compounds were characterized using spectroscopic and mass spectrometric analyses. RESULTS: Anthelmintic activity LC50 values for n-hexane, chloroform and acetone extracts were 47.85, 35.76 and 5.72 (mg/mL), respectively. Chromatographic separation of acetone extract afforded two bioactive epimers, identified as vincosamide (LC50 14.7 mg/mL) and strictosamide (LC50 12.8 mg/mL). Cytotoxicity evaluation showed that, below 200 µg/mL (400 µM), neither compound was toxic to the HeLa or MC3T3-E1 cells. CONCLUSION: Vincosamide and strictosamide could serve as novel scaffolds for the development of anthelmintic derivatives with improved potency and helminth selectivity.

Gelsedine-type alkaloids: Discovery of natural neurotoxins presented in toxic honey.

The fascinating collection and evaluation of natural products with enormous structural and chemical diversity can contribute to ensure human health and inspire potential drug discovery. We reported the identification of 14-(R)-hydroxy-gelsenicine (HGE), a new component from poisonous honey, which has recently caused multiple serious intoxications and deaths up on consumption. The prevalence, toxicity, toxicokinetics and metabolic profile of HGE were evaluated through in vitro and in vivo analyses. HGE is a very toxic substance and shows significant gender difference with LD50 of 0.125 mg kg-1 and 0.295 mg kg-1 for the female and male mice, respectively. Toxicokinetics test indicates that HGE has good bioavailability in rats, and is metabolized extensively, in which hydroxylation, reduction, N-demethyl ether and glucuronication are the major metabolic pathways. Additionally, HGE shows specific neurotoxicity by enhancing the binding of γ-aminobutyric acid (GABA) to its receptors. We found that flumazenil, a selective antagonist of GABA receptor, could effectively increase the survival of the tested animals, which provides a potential therapy for future clinical applications.

A Simple LC-MS Method for the Quantitation of Alkaloids in Endophyte-Infected Perennial Ryegrass.

The rapid identification and quantitation of alkaloids produced by Epichloë endophyte-infected pasture grass is important for the agricultural industry. Beneficial alkaloids, such as peramine, provide the grass with enhanced insect protection. Conversely, ergovaline and lolitrem B can negatively impact livestock. Currently, a single validated method to measure these combined alkaloids in planta does not exist. Here, a simple two-step extraction method was developed for Epichloë-infected perennial ryegrass (Lolium perenne L.). Peramine, ergovaline and lolitrem B were quantified using liquid chromatography-mass spectrometry (LC-MS). Alkaloid linearity, limit of detection (LOD), limit of quantitation (LOQ), accuracy, precision, selectivity, recovery, matrix effect and robustness were all established. The validated method was applied to eight different ryegrass-endophyte symbiota. Robustness was established by comparing quantitation results across two additional instruments; a triple quadruple mass spectrometer (QQQ MS) and by fluorescence detection (FLD). Quantitation results were similar across all three instruments, indicating good reproducibility. LOQ values ranged from 0.8 ng/mL to 6 ng/mL, approximately one hundred times lower than those established by previous work using FLD (for ergovaline and lolitrem B), and LC-MS (for peramine). This work provides the first highly sensitive quantitative LC-MS method for the accurate and reproducible quantitation of important endophyte-derived alkaloids.

Nogo-A/Pir-B/TrkB Signaling Pathway Activation Inhibits Neuronal Survival and Axonal Regeneration After Experimental Intracerebral Hemorrhage in Rats.

Intracerebral hemorrhage (ICH) leads to widespread pathological lesions in the brain, especially impacting neuronal survival and axonal regeneration. This study aimed to elucidate whether the Nogo-A (a myelin-related protein)/paired immunoglobulin-like receptor B (Pir-B)/tropomyosin receptor kinase B (TrkB) pathway could exert a regulatory effect in ICH. An ICH model was first established in Sprague Dawley rats, followed by different administrations of vehicle, k252a, or NSC 87877. The Morris water maze test was performed to observe ICH-induced cognitive dysfunction in rats. Rats in the ICH + NSC 87877 group showed better cognitive performance compared with those injected with vehicle or k252a. Neurobehavioral scores were identical. By harvesting brain tissues at different time points after ICH, we detected the expression levels of Nogo-A and PirB with western blot and immunofluorescence and found that they were markedly upregulated at 48 h after ICH. TUNEL and Fluoro-Jade B staining showed that NSC 87877 treatment attenuated ICH-induced apoptosis and neuronal death, whereas k252a treatment aggravated these pathological changes. The expression levels of growth-associated protein 43 (GAP43) and neurofilament 200 (NF200) were higher in the ICH + NSC 87877 group compared with the ICH + vehicle group, but were lower in the ICH + k252a group. Finally, we confirmed the protective role of p-TrkB/TrkB in ICH by western blot. To sum up, our study identified the inhibitory role of the Nogo-A/PirB/TrkB pathway in ICH; however, p-TrkB/TrkB may serve as a potential target for secondary brain injury post-ICH.

A single exposure to the tremorgenic mycotoxin lolitrem B inhibits voluntary motor activity and spatial orientation but not spatial learning or memory in mice.

The indole diterpenoid toxin lolitrem B is a tremorgenic agent found in the common grass species, perennial ryegrass (Lolium perenne). The toxin is produced by a symbiotic fungus Epichloë festucae (var. lolii) and ingestion of infested grass with sufficient toxin levels causes a movement disorder in grazing herbivores known as 'ryegrass staggers'. Beside ataxia, lolitrem B intoxicated animals frequently show indicators of cognitive dysfunction or exhibition of erratic and unpredictable behaviours during handling. Evidence from field cases in livestock and controlled feeding studies in horses have indicated that intoxication with lolitrem B may affect higher cortical or subcortical functioning. In order to define the role of lolitrem B in voluntary motor control, spatial learning and memory under controlled conditions, mice were exposed to a known dose of purified lolitrem B toxin and tremor, coordination, voluntary motor activity and spatial learning and memory assessed. Motor activity, coordination and spatial memory were compared to tremor intensity using a novel quantitative piezo-electronic tremor analysis. Peak tremor was observed as frequencies between 15 and 25Hz compared to normal movement at approximately 1.4-10Hz. A single exposure to a known tremorgenic dose of lolitrem B (2 mg/kg IP) induced measureable tremor for up to 72 h in some animals. Initially, intoxication with lolitrem B significantly decreased voluntary movement. By 25 h post exposure a return to normal voluntary movement was observed in this group, despite continuing evidence of tremor. This effect was not observed in animals exposed to the short-acting tremorgenic toxin paxilline. Lolitrem B intoxicated mice demonstrated a random search pattern and delayed latency to escape a 3 h post intoxication, however by 27 h post exposure latency to escape matched controls and mice had returned to normal searching behavior indicating normal spatial learning and memory. Together these data indicate that the tremor exhibited by lolitrem B intoxicated mice does not directly impair spatial learning and memory but that exposure does reduce voluntary motor activity in intoxicated animals. Management of acutely affected livestock suffering toxicosis should be considered in the context of their ability to spatially orientate with severe toxicity.

Bio-guided search of active indole alkaloids from Tabernaemontana catharinensis: Antitumour activity, toxicity in silico and molecular modelling studies.

Active plant metabolites have been used as prototype drugs. In this context, Tabernaemontana catharinensis (Apocynaceae) has been highlighted because of the presence of active indole alkaloids. Thus, this study aims the bio-guided search of T. catharinensis cytotoxic alkaloids. The chemical composition was identified by high-resolution mass spectrometry, and fractionation was performed by open column and preparative thin-layer chromatography, from plant stems. The enriched fractions were tested in vitro in tumour cells A375 (melanoma cell line) and A549 (adenocarcinomic human alveolar basal epithelial cells), and non-tumour Vero cells (African green monkey kidney epithelial cells). The alkaloids identified as active were submitted to in silico toxicity prediction by ADME-Tox and OSIRIS programs and, also, to molecular docking, using topoisomerase I (PDB ID: 1SC7) by iGEMDOCK. As a result, six sub-fractions were obtained, which were identified as containing 16-epi-affinine, 12-methoxy-n-methyl-voachalotine, affinisine, voachalotine, coronaridine hydroxyindoline and ibogamine, respectively. The affinisine-containing sub-fraction showed selective toxicity against A375, with an IC50 of 11.73 µg mL-1, and no cytotoxicity against normal cells (Vero). From the in silico toxicity test results, all indole alkaloid compounds had a low toxicity risk. The molecular docking data provided structural models and binding affinities of the plant's indole alkaloids and topoisomerase I. In summary, this bio-guided search revealed that the indole alkaloids from T. catharinensis display selective cytotoxicity in A375 tumour cells and toxicity in silico. Particularly, affinisine might be a chemotherapeutic for A375 melanoma cells.

Fluorescent Canthin-6-one Alkaloids from Simaba bahiensis: Isolation, Identification, and Cell-Labeling Properties.

Canthin-6-one alkaloids, which are present in plants of the genus Simaba, are natural compounds that are capable of acting as fluorescent probes. However, the chemical composition and fluorescent properties of most species of this genus have not been analyzed. The objective of this study was to characterize the fluorescent properties of an extract of S. bahiensis and identify the chemical entities responsible for these properties. In addition, the cell-labeling properties of the fluorescent dye from A and of the isolated compounds were characterized by confocal fluorescence microscopy and flow cytometry. One quassinoid and three fluorescent alkaloids were isolated from S. bahiensis, all compounds were identified by using NMR spectroscopy and high-resolution mass spectrometry. Staining experiments and HPLC-FL analysis shown that canthin-6-one alkaloids are the main green fluorescent compounds in the analyzed dyes. All compounds evaluated showed a cytoplasmic marker with a residence time of 24 h. The present study is the first to describe the presence of canthin-6-one alkaloids in S. bahiensis, in addition to demonstrating promising cell-labeling properties of fluorescent compounds from S. bahiensis with broad emission wavelengths.

Interaction between the barley allelochemical compounds gramine and hordenine and artificial lipid bilayers mimicking the plant plasma membrane.

Some plants affect the development of neighbouring plants by releasing secondary metabolites into their environment. This phenomenon is known as allelopathy and is a potential tool for weed management within the framework of sustainable agriculture. While many studies have investigated the mode of action of various allelochemicals (molecules emitted by allelopathic plants), little attention has been paid to their initial contact with the plant plasma membrane (PPM). In this paper, this key step is explored for two alkaloids, gramine and hordenine, that are allelochemicals from barley. Using in vitro bioassays, we first showed that gramine has a greater toxicity than hordenine towards a weed commonly found in northern countries (Matricaria recutita L.). Then, isothermal titration calorimetry was used to show that these alkaloids spontaneously interact with lipid bilayers that mimic the PPM. The greater impact of gramine on the thermotropic behaviour of lipids compared to hordenine was established by means of infrared spectroscopy. Finally, the molecular mechanisms of these interactions were explored with molecular dynamics simulations. The good correlation between phytotoxicity and the ability to disturb lipid bilayers is discussed. In this study, biophysical tools were used for the first time to investigate the interactions of allelochemicals with artificial PPM.

Chemical warfare between leafcutter ant symbionts and a co-evolved pathogen.

Acromyrmex leafcutter ants form a mutually beneficial symbiosis with the fungus Leucoagaricus gongylophorus and with Pseudonocardia bacteria. Both are vertically transmitted and actively maintained by the ants. The fungus garden is manured with freshly cut leaves and provides the sole food for the ant larvae, while Pseudonocardia cultures are reared on the ant-cuticle and make antifungal metabolites to help protect the cultivar against disease. If left unchecked, specialized parasitic Escovopsis fungi can overrun the fungus garden and lead to colony collapse. We report that Escovopsis upregulates the production of two specialized metabolites when it infects the cultivar. These compounds inhibit Pseudonocardia and one, shearinine D, also reduces worker behavioral defenses and is ultimately lethal when it accumulates in ant tissues. Our results are consistent with an active evolutionary arms race between Pseudonocardia and Escovopsis, which modifies both bacterial and behavioral defenses such that colony collapse is unavoidable once Escovopsis infections escalate.

Assessment of toxicity and differential antimicrobial activity of methanol extract of rhizome of Simaba ferruginea A. St.-Hil. and its isolate canthin-6-one.

ETHNOPHARMACOLOGICAL RELEVANCE: Simaba ferruginea A. St.-Hil., Simaroubaceae, popularly known as "calunga" is a typical subtropical shrub used in Central Brazil mainly for infection, anti-inflammatory, analgesic and gastric duodenal-ulcers. It presents in its composition the alkaloid canthin-6-one, an alkaloid indole ß-carboxylic. AIM: This study aims to investigate the toxicity, antimicrobial activities of methanol extract of Simaba ferruginea (MESf) and canthin-6-one by using different experimental models. METHODS: The present study evaluated the phytochemical analysis by high performance liquid chromatography (HPLC), toxicological potential of MESf and canthin-6-one, using the cytotoxicity, genotoxicity assays with CHO-K1 cells and in vivo acute test in mice. Antimicrobial activity was evaluated by the broth microdilution assays, while the antimicrobial mechanism of action was also assessed using different in vitro bacterial and fungal models. RESULTS: The HPLC analysis of MESf revealed the presence of canthin-6-one, kaempferol and morin. Differential in vitro toxicities were observed between MESf and canthin-6-one. In the cytotoxicity assay, MESf presented toxicity against CHO-K1, while canthin-6-one did not. In the case of in vitro genotoxicity, both showed to be potentially genotoxic. In the in vivo toxicity study, both MESf (up to 1000 mg/kg) and cantin-6-one (up to 100 mg/kg) caused no toxicologically relevant alterations and are thus considered not to be toxic. MESf was shown to be relatively safe with NOAEL (100 mg/kg) when administrate in mice. Both MESf and canthin-6-one also showed differential antimicrobial activities. On one hand, MESf demonstrated good spectrum of antibacterial action against Staphylococcus aureus (MIC 12.5 µg/mL) and Escherichia coli (MIC 25 µg/mL) and moderate activity against Enterococcus faecalis and Shigella flexneri (MIC 200 µg/mL) but no antifungal effect. On the hand, canthin-6-one showed no antibacterial activity, except against Staphylococcus aureus (100 µg/mL), but potent in vitro fungicidal activity against clinically important Aspergillus niger and Candida species at MFC intervals ranging from 3.12 to 25 µg/mL. Both MESf and canthin-6-one were bacteriostatic in action. MESf antimicrobial mechanism of actions are associated with changes in the permeability of bacterial membranes, evidenced by the increased entry of hydrophobic antibiotic in Shigella flexneri, intense K+ efflux (Shigella flexneri, Staphylococcus aureus) and nucleotides leakage (Staphylococcus aureus). In the antifungal mode of action, canthin-6-one inhibited Saccharomyces cerevisiae growth and including alteration in the cell membrane of Neurospora crassa. CONCLUSION: The results of this work demonstrated the differential antimicrobial activities of MESf and its alkaloid isolate, canthin-6-one with antibacterial and antifungal activities, respectively. The present study support the popular use of Simaba ferruginea in combatting afflictions related to bacterial infections, and demonstrate that canthin-6-one as a promising antifungal agent. Both MESf and canthin-6-one are considered non-toxic based on the in vitro toxicological study.

Cytotoxic properties of the alkaloid rutaecarpine and its oligocyclic derivatives and chemical modifications to enhance water-solubility.

The alkaloid rutaecarpine and its derivatives have been described as cytotoxic and hold potential as antitumor agents. Nevertheless, their synthesis is demanding and compounds display poor water solubility. Herein, we describe the synthesis of two sets of rutaecarpine derivatives with amine functions to improve solubility. Using a classic shake-flask experiment and a potentiometric titration platform, the water solubility of the compounds was determined. Solubility improved significantly with the amine functions connected over the indole-N atom. Reduction of metabolic activity and cell viability on HeLa cells was in the same range or better for these derivatives compared to the chemically unaltered parent compounds prepared in a new synthetic procedure established in our group.

Pharmacoinformatics study of Piperolactam A from Piper betle root as new lead for non steroidal anti fertility drug development.

Fertility control is a burning problem all over the world to regulate population overflow and maintain ecological balance. This study is an in-silico approach to explore a non-steroidal lead as contraceptive agent in order to avoid several contraindications generated by steroidal analogues. Piperolactam A, an aristolactam isolated from Piper betle Linn. showed binding affinity towards estrogen and progesterone receptor as -8.9 and -9.0Kcal/mol (inhibition constant Ki=0.294µM and 0.249µM) respectively which is even larger than that of reported antagonists such as Rohitukine and OrgC (binding affinity -8.7 and -8.4Kcal/mol; Ki 0.443µM and 0.685µM respectively). The binding site exploration displayed more hydrogen bonding of Piperolactam A (His 524, Leu 346, Thr 347) than Rohitukine and OrgC (Leu 718) with associated receptors which was further confirmed by molecular dynamics simulations. The drug-likeliness of the compound has been proved from its tally with Lipinsky's Rule of Five and lowered toxicity such as cardiac toxicity, liver toxicity, mutagenicity and ecological toxicity. Endocrine disruptome and later docking guided molecular simulations revealed that Piperolactam A has weaker binding affinity and/or lower probability of binding with nuclear receptors especially hERG and cytochrome P450. The high Caco-2 permeability suggested more bioavailability hence more therapeutic efficacy of the drug.

A novel monoterpenoid indole alkaloid with anticancer activity from Melodinus khasianus.

A novel monoterpenoid indole alkaloid with unprecedented 6/5/6/4/6 fused rings, khasuanine A (1), was isolated from the roots of Melodinus khasianus. The structure was determined by extensive analysis of its HR-MS, 1D-, and 2D-NMR spectra. Khasuanine A markedly inhibited the proliferation of PC3 cell with IC50 value of 0.45µM. Further study showed that khasuanine A was able to induce the apoptosis of PC3 cells by activation of caspase 3 and p53, and by inhibition of Bcl-2.

Mesembrine alkaloids: Review of their occurrence, chemistry, and pharmacology.

ETHNOPHARMACOLOGICAL RELEVANCE: Mesembrine alkaloids are considered to be the primary active constituents of the South African medicinal plant Sceletium tortuosum (L.) N.E.Br. (Aizoaceae), and it is used as the dried or fermented aerial material from the plant, which is known as kanna (aka, channa, kougoed). Traditional regional use ranged from relieving thirst, mild analgesia, and alteration of mood. Current interest has focused primarily on the antidepressant action of preparations based on the plant and commercialization is expanding the recognition and availability of these preparations. MATERIALS AND METHODS: Searches for the keywords "Sceletium or mesembrine" were performed in "PubMed-NCBI", "Chemical Abstracts SciFinder" and "Thomson Reuters Web of Science" databases in addition to the inclusion of references cited within prior reviews and scientific reports. Additionally the "SciFinder" database was searched using 3a-phenyl-cis-octahydroindole in the SciFinder Substructure Module (SSM). Plant taxonomy was validated by the database "The Plant List". RESULTS: This review focuses on the chemistry, analysis, and pharmacology of the mesembrine alkaloids. Despite a long history of medicinal used and research investigation, there has been a renewed interest in the pharmacological properties of the mesembrine alkaloids and much of the pharmacology has only recently been published. The two major active alkaloids mesembrine and mesembrenone are still in the process of being more fully characterized pharmacologically. They are serotonin reuptake inhibitors, which provides a rationale for the plant's traditional use as an antidepressant, but other actions are beginning to appear in the literature. Additionally, mesembrenone has reasonably potent PDE4 inhibitory activity. This review intends to provide an overview of the available literature, summarize the current findings, and put them in perspective with earlier studies and reviews.