Identification of a new cyathane diterpene that induces mitochondrial and autophagy-dependent apoptosis and shows a potent in vivo anti-colorectal cancer activity

Exploring natural products as apoptosis modulators in cancers: insights into natural product-based therapeutic strategies

Cancer remains a leading cause of mortality globally, necessitating ongoing research and development of innovative therapeutic strategies. Natural products from plants, herbs, and marine species have shown great promise as anti-cancer therapies due to their bioactive components that alter cellular pathways, particularly apoptosis. This review explores the mechanism by which natural chemicals trigger the apoptosis of cancerous cells, which is crucial for eliminating them and halting tumor growth. These can affect the mitochondrial process by controlling the Bcl-2 protein family, increasing cytochrome c release, and activating caspases. They also activate death receptors like Fas and TRAIL to enhance the extrinsic apoptotic pathway. We focus on the main signaling channels involved, such as the endoplasmic reticulum (ER) stress-mediated apoptosis, extrinsic death receptor, and intrinsic mitochondrial pathways. The review explores the role of natural substances such as polyphenols, terpenoids, alkaloids, and flavonoids in promoting apoptotic cell death and increasing cancer cell susceptibility, potentially aiding in cancer treatments and the potential of combining natural products with traditional chemotherapeutic medicines to combat medication resistance and enhance therapeutic efficacy. Understanding cancer development involves inhibiting cell proliferation, regulating it, targeting apoptosis pathways, and using plant and marine extracts as apoptotic inducers.

Anticancer diterpenes of African natural products: Mechanistic pathways and preclinical developments

BACKGROUND

The African continent is home to five biodiversity hotspots, boasting an immense wealth of medicinal flora, fungi and marine life. Diterpenes extracted from such natural products have compelling cytotoxic activities that warrant further exploration for the drug market, particularly in cancer therapy, where mortality rates remain elevated worldwide.

PURPOSE

To demonstrate the potential of African natural products on the global stage for cancer therapy development and provide an in-depth analysis of the current literature on the activity of cancer cytotoxic diterpenes from African natural sources (to our knowledge, the first of its kind); not only to reveal the most promising candidates for clinical development, but to demonstrate the importance of preserving the threatened ecosystems of Africa.

METHODS

A comprehensive search by means of the PRISMA strategy was conducted using electronic databases, namely Web of Science, PubMed, Google Scholar and ScienceDirect. The search terms employed were 'diterpene & mechanism & cancer' and 'diterpene & clinical & cancer'. The selection process involved assessing titles in English, Portuguese and Spanish, adhering to predefined eligibility criteria. The timeframe for inclusion spanned from 2010 to 2023, resulting in 218 relevant papers. Chemical structures were visualized using ChemDraw 21.0, PubChem was utilized to search for CID numbers.

RESULTS

Despite being one of the richest biodiverse zones in the world, African natural products are proportionally underreported compared to Asian countries or otherwise. The diterpenes andrographolide (Andrographis paniculata), forskolin (Coleus forskohlii), ent-kauranes from Isodon spp., euphosorophane A (Euphorbia sororia), cafestol & kahweol (Coffea spp.), macrocylic jolkinol D derivatives (Euphorbia piscatoria) and cyathane erinacine A (Hericium erinaceus) illustrated the most encouraging data for further cancer therapy exploration and development.

CONCLUSIONS

Diterpenes from African natural products have the potential to be economically significant active pharmaceutical and medicinal ingredients, specifically focussed on anticancer therapeutics.

Genome-wide characterization and metabolite profiling of Cyathus olla: insights into the biosynthesis of medicinal compounds

Cyathus olla, belonging to the genus Cyathus within the order Agaricales, is renowned for its bird's nest-like fruiting bodies and has been utilized in folk medicine. However, its genome remains poorly understood. To investigate genomic diversity within the genus Cyathus and elucidate biosynthetic pathways for medicinal compounds, we generated a high-quality genome assembly of C. olla with fourteen chromosomes. The comparative genome analysis revealed variations in both genomes and specific functional genes within the genus Cyathus. Phylogenomic and gene family variation analyses provided insights into evolutionary divergence, as well as genome expansion and contraction in individual Cyathus species and 36 typical Basidiomycota. Furthermore, analysis of LTR-RT and Ka/Ks revealed apparent whole-genome duplication (WGD) events its genome. Through genome mining and metabolite profiling, we identified the biosynthetic gene cluster (BGC) for cyathane diterpenes from C. olla. Furthermore, we predicted 32 BGCs, containing 41 core genes, involved in other bioactive metabolites. These findings represent a valuable genomic resource that will enhance our understanding of Cyathus species genetic diversity. The genome analysis of C. olla provides insights into the biosynthesis of medicinal compounds and establishes a fundamental basis for future investigations into the genetic basis of chemodiversity in this significant medicinal fungus.

Selaginellin derivatives from Selaginella tamariscina and evaluation for anti-breast cancer activity

A phytochemical investigation of Selaginella tamariscina led to the isolation of 17 selaginellin derivatives. Their inhibitory activities against breast cancer cells were screened, and preliminary structure-activity relationships were also established. Among them, dimeric selaginellin 17 showed potential activity against MDA-MB-231 cells with an IC50 value of 3.2 ± 0.1 μM, corresponding to 4-fold higher potency than the reference compound 5-FU (IC50 14.8 ± 0.2 μM). Mechanistic studies indicated that 17 could cause G2/M phase arrest in MDA-MB-231 cells and induce apoptosis accompanied by increased ROS levels.

Targeting Prohibitins to Inhibit Melanoma Growth and Overcome Resistance to Targeted Therapies

Despite important advances in the treatment of metastatic melanoma with the development of MAPK-targeted agents and immune checkpoint inhibitors, the majority of patients either do not respond to therapies or develop acquired resistance. Furthermore, there is no effective targeted therapy currently available for BRAF wild-type melanomas (approximately 50% of cutaneous melanoma). Thus, there is a compelling need for new efficient targeted therapies. Prohibitins (PHBs) are overexpressed in several types of cancers and implicated in the regulation of signaling networks that promote cell invasion and resistance to cell apoptosis. Herein, we show that PHBs are highly expressed in melanoma and are associated with not only poor survival but also with resistance to BRAFi/MEKi. We designed and identified novel specific PHB inhibitors that can inhibit melanoma cell growth in 3D spheroid models and a large panel of representative cell lines with different molecular subtypes, including those with intrinsic and acquired resistance to MAPKi, by significantly moderating both MAPK (CRAF-ERK axis) and PI3K/AKT pathways, and inducing apoptosis through the mitochondrial pathway and up-regulation of p53. In addition, autophagy inhibition enhances the antitumor efficacy of these PHB ligands. More important, these ligands can act in synergy with MAPKi to more efficiently inhibit cell growth and overcome drug resistance in both BRAF wild-type and mutant melanoma. In conclusion, targeting PHBs represents a very promising therapeutic strategy in melanoma, regardless of mutational status.

Secondary Metabolites of Bird's Nest Fungi: Chemical Structures and Biological Activities

Bird's nest fungi, a general term for species in the family Nidulariaceae, are named for their fruiting bodies that resemble bird's nests. Two of their members, Cyathus stercoreus (Schw.) de Toni. and Cyathus striatus Will. ex Pers., are known as medicinal fungi in Chinese medicine. Bird's nest fungi produce a variety of secondary metabolites that provide natural materials for screening and developing medicinal compounds. This review presents a systematic summary of the literature on the secondary metabolites of bird's nest fungi up to January 2023, including 185 compounds, mainly cyathane diterpenoids, with prominently characterized antimicrobial and antineurodegenerative activities. Our work aims to advance our understanding of bird's nest fungi and support studies on their natural product chemistry, pharmacology, and biosynthesis of secondary metabolites.

SCP-7, a germacrane-type sesquiterpene lactone derivative, induces ROS-mediated apoptosis in NSCLC cells in vitro and in vivo

Scabertopin (SCP), an abundant germacrane-type sesquiterpene lactone (SLC) isolated from Elephantopus scaber, was selected as a reference compound for modification and evaluation as anticancer agents for non-small cell lung cancer (NSCLC) treatment. All derivatives (SCP-1-SCP-13) except for SCP-3 showed potential inhibitory effect (IC50 5.2-9.7 μM) against A549 cells. The most promising compound SCP-7 also showed good cytotoxic activity against another two NSCLC cell lines (H1299 and H460), with IC50 value of 4.4 and 8.9 μM, respectively. Furthermore, SCP-7 could induce apoptotic cell death that was associated with the increased reactive oxygen species (ROS) generation, the loss of mitochondrial membrane potential, Bcl-2 family proteins modulation, caspases-3 and PARP cleavage. In addition, SCP-7 also inhibited cell growth by increasing Bax expression and reducing the Ki-67 positive cells in vivo, but there were no obvious toxic and side effects on internal organs. Mechanistically, PharmMapper, molecular docking and Western blot analysis revealed that SCP-7 might interact with the epidermal growth factor receptor (EGFR) and inhibit its expression in lung cancer cells. Together, above results suggest further effective application of SCP-7 as a potential anti-tumor agent in the treatment of NSCLC.

Progress in biological activities and biosynthesis of edible fungi terpenoids

The edible fungi have both edible and medicinal functions, in which terpenoids are one of the most important active ingredients. Terpenoids possess a wide range of biological activities and show great potential in the pharmaceutical and healthcare industries. In this review, the diverse biological activities of edible fungi terpenoids were summarized with emphasis on the mechanism of anti-cancer and anti-inflammation. Subsequently, this review focuses on advances in knowledge and understanding of the biosynthesis of terpenoids in edible fungi, especially in the generation of sesquiterpenes, diterpenes, and triterpenes. This paper is aim to provide an overview of biological functions and biosynthesis developed for utilizing the terpenoids in edible fungi.

Thirteen cyathane diterpenoids with acetylcholinesterase inhibitory effects from the fungus Cyathus africanus

Eight undescribed cyathane diterpenoids, representative specialised metabolites of the genus Cyathus, named cyathins Q-X, along with five known congeners, were isolated from the liquid fermentation of Cyathus africanus. Their structures and absolute configurations were elucidated by integrating NMR spectroscopic analyses, electronic circular dichroism (ECD) calculations, and X-ray diffraction. Reasonable correction to the C-12 configuration of cyathin I was corroborated by the crystal data. The structural identification in this research expanded the number of candidates to allow for more bioactivity-screening options. Among them, (12S)-11α,14α-epoxy-13α,14β,15-trihydroxycyath-3-ene displayed significant acetylcholinesterase (AChE) inhibitory effect with an IC₅₀ value of 4.60 ± 0.85 μM. Molecular docking studies were also performed to unravel the underlying modes of interactions with the active sites of AChE for active compounds.

Promising Anti-cancer Therapeutics From Mushrooms: Current Findings and Future Perceptions

BACKGROUND

Nowadays, medicines derived from natural sources have drawn much attention as potential therapeutic agents in the suppression and treatment of cancer because of their low toxicity and fewer side effects.

OBJECTIVE

The present review aims to assess the currently available knowledge on the ethnomedicinal uses and pharmacological activities of bioactive compounds obtained from medicinal mushrooms towards cancer treatment.

METHODS

A literature search has been conducted for the collection of research papers from universally accepted scientific databases. These research papers and published book chapters were scrutinized to retrieve information on ethnomedicinal uses of mushrooms, different factors involved in cancer cell proliferation, clinical and in silico pharmaceutical studies made for possible treatments of cancer using mushroom derived compounds. Overall, 241 articles were retrieved and reviewed from the year 1970 to 2020, out of which 98 relevant articles were finally considered for the preparation of this review.

RESULTS

This review presents an update on the natural bioactive substances derived from medicinal mushrooms and their role in inhibiting the factors responsible for cancer cell proliferation. Along with it, the present review also provides information on the ethnomedicinal uses, solvents used for extraction of anti-cancer metabolites, clinical trials, and in silico studies that were undertaken towards anticancer drug development from medicinal mushrooms.

CONCLUSION

The present review provides extensive knowledge on various anti-cancer substances obtained from medicinal mushrooms, their biological actions, and in silico drug designing approaches, which could form a basis for the development of natural anti-cancer therapeutics.

Pro-Health and Anti-Cancer Activity of Fungal Fractions Isolated from Milk-Supplemented Cultures of Lentinus (Pleurotus) Sajor-caju

The present study aimed to demonstrate Lentinus (formerly Pleurotus) sajor-caju (PSC) as a good source of pro-health substances. It has also shown that supplementation of its culture medium with cow milk may further improve its beneficial properties. Intracellular fractions from fungi grown on a medium supplemented with cow milk were analyzed using various biochemical methods for determination of the nutrient composition. Furthermore, anti-cancer properties of selected extracts were investigated on colorectal cancer cell lines (HT-29, LS 180, and SW948) in vitro. Biochemical analysis showed enrichment in health-enhancing compounds, such as proteins or polysaccharides (about 3.5- and 4.5-fold increase in concentration of proteins and carbohydratesin extracts of mycelia cultured on whole milk (PSC2-I), respectively), with a decrease in the level of free radicals (10-fold decrease in extract grown on milk and medium mixture (1:1) (PSC3-II)), which was related to increased catalase and superoxide dismutase activity (7.5-fold increase in catalase activity and 5-fold in SOD activity in PSC3-II compared to the control). Moreover, the viability of the cancer cells was diminished (to 60.0 ± 6.8% and 40.0 ± 8.6% of the control, on HT-29 and SW948 cells, respectively), along with pro-apoptotic (to 18.8 ± 11.8 and 14.7 ± 8.0% towards LS 180 and SW948 cells, respectively) and NO-secreting effects (about 2-fold increase) of the extracts. This study suggests that PSC has multiple nutritional and anti-cancer properties and can be used as a source of healthy biomolecules in modern medicine or functional foods.

Natural Products Targeting the Mitochondria in Cancers

There are abundant sources of anticancer drugs in nature that have a broad prospect in anticancer drug discovery. Natural compounds, with biological activities extracted from plants and marine and microbial metabolites, have significant antitumor effects, but their mechanisms are various. In addition to providing energy to cells, mitochondria are involved in processes, such as cell differentiation, cell signaling, and cell apoptosis, and they have the ability to regulate cell growth and cell cycle. Summing up recent data on how natural products regulate mitochondria is valuable for the development of anticancer drugs. This review focuses on natural products that have shown antitumor effects via regulating mitochondria. The search was done in PubMed, Web of Science, and Google Scholar databases, over a 5-year period, between 2015 and 2020, with a keyword search that focused on natural products, natural compounds, phytomedicine, Chinese medicine, antitumor, and mitochondria. Many natural products have been studied to have antitumor effects on different cells and can be further processed into useful drugs to treat cancer. In the process of searching for valuable new drugs, natural products such as terpenoids, flavonoids, saponins, alkaloids, coumarins, and quinones cover the broad space.

Ganoderic acid D induces synergistic autophagic cell death except for apoptosis in ESCC cells

ETHNOPHAMACOLOGICAL RELEVANCE

Ganoderma lucidum has been used as a medicinal mushroom for more than 2000 years in China. Ganoderic acid D (GAD) as a representative active triterpenoid from Ganoderma lucidum is known to possess anticancer activity. However, the mechanism involved in its anticancer cell process is still largely elusive.

AIM OF THE STUDY

Our study aimed to investigate the anticancer effects of GAD on the esophageal squamous cell carcinoma (ESCC) cells and the underlying mechanisms at the cell level.

MATERIALS AND METHODS

EC9706 and Eca109 cells were treated with GAD (0, 10, 20, 40 μM) for 24 h. The cell viability, cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), apoptosis rate, caspase-3 activity, autophagic flux, lysosomal function were examined. Cell cycle, apoptotic, autophagy and mTOR signal pathway related proteins such as P53, Cyclin B1, CytoC, PARP, Beclin-1, P62, LC3, PI3K, AKT and mTOR were analyzed by Western blot approach.

RESULTS

GAD inhibited cell proliferation and induced both apoptosis and autophagic cell death. In particular, we found that in the early stage of the autophagic process, GAD could initiate and enhance the autophagy signal while in the late stage it on the contrary could block the autophagic flux by impairing the autophagosome-lysosome fusion and inhibited the lysosomal degradation. Besides the autophagic cell death, GAD also induced the apoptosis mediated by caspase-related process in parallel. The mechanism involved for the synergistic apoptotic and autophagic cell death was also explored. We found that GAD down-regulated the expression of PI3K, AKT and mTOR phosphorylated proteins in the mTOR signaling pathway which thus led to the synergistic effect on apoptosis and autophagic cell death in the ESCC cells.

CONCLUSIONS

In summary, this study has documented that GAD may inhibit cell proliferation through the mTOR pathway in ESCC cells, and induce synergistic apoptosis and autophagic cell death by disrupting the autophagic flux. This work therefore also suggests that GAD may be used as an efficient anticancer adjuvant for ESCC cancer therapy.

Elephantopinolide A-P, germacrane-type sesquiterpene lactones from Elephantopus scaber induce apoptosis, autophagy and G2/M phase arrest in hepatocellular carcinoma cells

Chromatographic purification of Elephantopus scaber led to 16 new germacrane-type sesquiterpene lactones (1-16), named elephantopinolide A-P, along with a known analogue (17). Their structures were confirmed by comprehensive spectroscopic analyses, single-crystal X-ray diffraction, and comparison between the experimental and calculated ECD spectra. Their hepatocellular inhibition activities against Hep3B and HepG2 cells were screened by MTT assay, and the structure-activity relationships were examined. The results revealed that 10 (IC50 value of 2.83 μM and 1.98 μM) is more potent than sorafenib. The underlying mechanism study demonstrated that 10 could markedly induce apoptosis accompanied by increased ROS production and decreased mitochondrial membrane potential, resulting in the autophagy and G2/M phase cell arrest in Hep3B and HepG2 cells. Furthermore, signal pathways including MAPKs and AKT may play important roles in 10-induced hepatocellular carcinoma cells death.

Erinacine A and related cyathane diterpenoids: Molecular diversity and mechanisms underlying their neuroprotection and anticancer activities

The presence of a fused 5/6/7 tricyclic core characterizes the group of cyathane diterpene natural products, that include more than 170 compounds, isolated from fungi such as Cyathus africanus and Hericium erinaceus. These compounds have a common biosynthetic precursor (cyatha-3,12-diene) and can be produced bio- or hemi-synthetically, or via total syntheses. Cyathane diterpenes display a range of pharmacological properties, including anti-inflammatory (possibly through binding to the iNOS protein) and neuroprotective effects. Many cyathanes like cyahookerin C, cyathin Q and cyafranines B and G can stimulate neurite outgrowth in cells, whereas conversely a few molecules (such as scabronine M) inhibit NGF-stimulated neurite outgrowth. The main anticancer cyathanes are erinacine A and cyathins Q and R, with a capacity to trigger cancer cell death dependent on the production of reactive oxygen species (ROS). These compounds, active both in vitro and in vivo, activate different signaling pathways in tumor cells to induce apoptosis (and autophagy) and to upregulate the expression of several proteins implicated in the organization and functioning of the actin cytoskeleton. An analysis of the functional analogy between erinacine A and other natural products known to interfere with the actin network in a ROS-dependent manner (notably cucurbitacin B) further supports the idea that erinacine A functions as a perturbator of the cytoskeleton organization. Collectively, we provide an overview of the molecular diversity of cyathane diterpenes and the main mechanisms of action of the lead compounds, with the objective to encourage further research with these fungal products. The anticancer potential of erinacine A deserves further attention but it will be necessary to better characterize the implicated targets and signaling pathways.

Phenylpropanoid derivatives from the fruit of Crataegus pinnatifida Bunge and their distinctive effects on human hepatoma cells

Ten undescribed phenylpropanoid derivatives including four pairs of enantiomers and two 8-9' linked neolignans, together with fifteen known ones were isolated from the fruit of Crataegus pinnatifida Bunge. Their structures were established by comprehensive spectroscopic analyses. Enantiomers were separated successfully by chiral chromatographic column and their absolute configurations were determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. The in vitro cytotoxicity of the isolates were evaluated against two human hepatocellular carcinoma, HepG2 and Hep3B cells. Among them, (±)-crataegusanoid A, (±)-crataegusanoid B and crataegusanoid F exhibited moderate cytotoxicity. Interestingly, the different absolute configurations of (±)-crataegusanoid A and B demonstrated enantioselective cytotoxicity in HepG2 cells. Further flow cytometry analysis indicated that both (-)-crataegusanoid A and (-)-crataegusanoid B performed more significant effects on cell apoptosis, autophagy, and cell cycle progression compared with their enantiomers (+)-crataegusanoid A and (+)-crataegusanoid B. In addition, the results revealed that these two pairs of enantiomers induced protective autophagy in HepG2 cells.

Cyathane Diterpenes from Cultures of the Bird's Nest Fungus Cyathus hookeri and Their Neurotrophic and Anti-neuroinflammatory Activities

Six new cyathane diterpenoids, cyahookerins A-F (1-6), as well as nine known analogues (7-15), were isolated from the liquid culture of the basidiomycete Cyathus hookeri. Their structures were elucidated on the basis of extensive spectroscopic analyses (1D and 2D NMR, HRESIMS, and ECD), and the absolute configurations of compounds 1 and 4 were determined by single-crystal X-ray crystallography. Compounds 1 and 2 represent the first unusual cyathane acetals featuring a dioxolane ring. Compounds 1-6 displayed differential nerve growth factor-induced neurite outgrowth-promoting activity in PC-12 cells at concentrations of 10 μM. In addition, cyahookerin B (2), cyathin E (9), cyathin B₂ (12), and cyathin Q (13) showed significant nitric oxide production inhibition in Lipopolysaccharide (LPS)-activated BV-2 microglial cells with IC₅₀ values of 12.0, 6.9, 10.9, and 9.1 μM, respectively. Similar binding modes of the four compounds were indicated by molecular-docking studies, and structure-activity relationships are discussed.

Biological and chemical diversity go hand in hand: Basidiomycota as source of new pharmaceuticals and agrochemicals

The Basidiomycota constitutes the second largest higher taxonomic group of the Fungi after the Ascomycota and comprises over 30.000 species. Mycelial cultures of Basidiomycota have already been studied since the 1950s for production of antibiotics and other beneficial secondary metabolites. Despite the fact that unique and selective compounds like pleuromutilin were obtained early on, it took several decades more until they were subjected to a systematic screening for antimicrobial and anticancer activities. These efforts led to the discovery of the strobilurins and several hundreds of further compounds that mainly constitute terpenoids. In parallel the traditional medicinal mushrooms of Asia were also studied intensively for metabolite production, aimed at finding new therapeutic agents for treatment of various diseases including metabolic disorders and the central nervous system. While the evaluation of this organism group has in general been more tedious as compared to the Ascomycota, the chances to discover new metabolites and to develop them further to candidates for drugs, agrochemicals and other products for the Life Science industry have substantially increased over the past decade. This is owing to the revolutionary developments in -OMICS techniques, bioinformatics, analytical chemistry and biotechnological process technology, which are steadily being developed further. On the other hand, the new developments in polythetic fungal taxonomy now also allow a more concise selection of previously untapped organisms. The current review is dedicated to summarize the state of the art and to give an outlook to further developments.

Induction of autophagy and autophagy-dependent apoptosis in diffuse large B-cell lymphoma by a new antimalarial artemisinin derivative, SM1044

Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma. R-CHOP is currently the standard therapy for DLBCL, but the prognosis of refractory or recurrent patients remains poor. In this study, we synthesized a new water-soluble antimalarial drug artemisinin derivative, SM1044. The treatment of DLBCL cell lines with SM1044 induces autophagy-dependent apoptosis, which is directed by an accelerated degradation of the antiapoptosis protein Survivin, via its acetylation-dependent interaction with the autophagy-related protein LC3-II. Additionally, SM1044 also stimulates the de novo synthesis of ceramide, which in turn activates the CaMKK2-AMPK-ULK1 axis, leading to the initiation of autophagy. Our findings not only elucidate the mechanism of autophagy-dependent apoptosis in DLBCL cells, but also suggest that SM1044 is a promising therapeutic molecule for the treatment of DLBCL, along with R-CHOP regimen.

Polyoxygenated cyathane diterpenoids from the mushroom Cyathus africanus, and their neurotrophic and anti-neuroinflammatory activities

In a previous study, we reported ten new polyoxygenated cyathane diterpenoids, neocyathins A-J, and their anti-neuroinflammatory effects from the liquid culture of the medicinal Basidiomycete Cyathus africanus. In the present study, eight new highly polyoxygenated cyathane diterpenoids, named neocyathins K-R (1-8), were isolated from the solid culture of C. africanus cultivated on cooked rice, together with three known congeners (9-11). The structures and the absolute configurations of the new compounds were elucidated through comprehensive NMR and HRESIMS spectroscopic data, electronic circular dichroism (ECD) data, and chemical conversion. Compounds 1 and 2 represent the first reported naturally occurring compounds with 4,9-seco-cyathane carbon skeleton incorporating an unprecedented medium-sized 9/7 fused ring system, while the 3,4-seco-cyathane derivative (3) was isolated from Cyathus species for the first time. All compounds were evaluated for their neurotrophic and anti-neuroinflammatory activity. All the isolates at 1-25 μM displayed differential nerve growth factor (NGF)-induced neurite outgrowth-promoting activity in PC-12 cells, while one of the compounds, allocyathin B₂ (11), inhibited NO production in lipopolysaccharide (LPS)-stimulated microglia BV-2 cells. In addition, molecular docking studies showed that compound 11 generated interactions with the inducible nitric oxide synthase (iNOS) protein.

Molecular Diversity and Potential Anti-neuroinflammatory Activities of Cyathane Diterpenoids from the Basidiomycete Cyathus africanus

Ten new polyoxygenated cyathane diterpenoids, named neocyathins A–J (1–10), together with four known diterpenes (11–14), were isolated from the liquid culture of the medicinal basidiomycete fungus Cyathus africanus. The structures and configurations of these new compounds were elucidated through comprehensive spectroscopic analyses including 1D NMR, 2D NMR (HSQC, HMBC, NOESY) and HRESIMS, and electronic circular dichroism (ECD) data. Neuroinflammation is implicated in the pathogenesis of various neurodegenerative diseases, such as Alzheimers’ disease (AD). All isolated compounds were evaluated for the potential anti-neuroinflammatory activities in BV2 microglia cells. Several compounds showed differential effects on the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-stimulated and Aβ_1–42-treated mouse microglia cell line BV-2. Molecular docking revealed that bioactive compounds (e.g., 11) could interact with iNOS protein other than COX-2 protein. Collectively, our results suggested that this class of cyathane diterpenoids might serve as important lead compounds for drug discovery against neuroinflammation in AD.

Diterpenes and Their Derivatives as Potential Anticancer Agents

As therapeutic tools, diterpenes and their derivatives have gained much attention of the medicinal scientists nowadays. It is due to their pledging and important biological activities. This review congregates the anticancer diterpenes. For this, a search was made with selected keywords in PubMed, Science Direct, Web of Science, Scopus, The American Chemical Society and miscellaneous databases from January 2012 to January 2017 for the published articles. A total 28, 789 published articles were seen. Among them, 240 were included in this study. More than 250 important anticancer diterpenes and their derivatives were seen in the databases, acting in the different pathways. Some of them are already under clinical trials, while others are in the nonclinical and/or pre-clinical trials. In conclusion, diterpenes may be one of the lead molecules in the treatment of cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Euphorbia factor L2 induces apoptosis in A549 cells through the mitochondrial pathway

Euphorbia factor L2, a lathyrane diterpenoid isolated from caper euphorbia seed (the seeds of Euphorbia lathyris L.), has been traditionally applied to treat cancer. This article focuses on the cytotoxic activity of Euphorbia factor L2 against lung carcinoma A549 cells and the mechanism by which apoptosis is induced. We analyzed the cytotoxicity and related mechanism of Euphorbia factor L2 with an MTT assay, an annexin V-FITC/PI test, a colorimetric assay, and immunoblotting. Euphorbia factor L2 showed potent cytotoxicity to A549 cells. Euphorbia factor L2 led to an increase in reactive oxygen species (ROS) generation, a loss of mitochondrial electrochemical potential, release of cytochrome c, activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase, suggesting that Euphorbia factor L2 induced apoptosis through a mitochondrial pathway. The cytotoxic activity of Euphorbia factor L2 in A549 cells and the related mechanisms of apoptotic induction provide support for the further investigation of caper euphorbia seeds.

Synthesis, crystal structure, cytotoxicity and action mechanism of Zn(ii) and Mn(ii) complexes with 4-([2,2′:6′,2′′-terpyridin]-4′-yl)-N,N-diethylaniline as a ligand

Two metallo-complexes inhibited telomerase by interacting with c-myc G4-DNA and induced cell cycle arrest at the S phase.