Cytotoxic constituents of the roots of Ekmanianthe longiflora

A review of natural products and small-molecule therapeutics acting on central nervous system malignancies: Approaches for drug development, targeting pathways, clinical trials, and challenges

In 2021, the World Health Organization released the fifth edition of the central nervous system (CNS) tumor classification. This classification uses histopathology and molecular pathogenesis to group tumors into more biologically and molecularly defined entities. The prognosis of brain cancer, particularly malignant tumors, has remained poor worldwide, approximately 308,102 new cases of brain and other CNS tumors were diagnosed in the year 2020, with an estimated 251,329 deaths. The cost and time-consuming nature of studies to find new anticancer agents makes it necessary to have well-designed studies. In the present study, the pathways that can be targeted for drug development are discussed in detail. Some of the important cellular origins, signaling, and pathways involved in the efficacy of bioactive molecules against CNS tumorigenesis or progression, as well as prognosis and common approaches for treatment of different types of brain tumors, are reviewed. Moreover, different study tools, including cell lines, in vitro, in vivo, and clinical trial challenges, are discussed. In addition, in this article, natural products as one of the most important sources for finding new chemotherapeutics were reviewed and over 700 reported molecules with efficacy against CNS cancer cells are gathered and classified according to their structure. Based on the clinical trials that have been registered, very few of these natural or semi-synthetic derivatives have been studied in humans. The review can help researchers understand the involved mechanisms and design new goal-oriented studies for drug development against CNS malignancies.

In Silico and In Vitro Study of Janus Kinases Inhibitors from Naphthoquinones

Janus kinases (JAKs) are involved in numerous cellular signaling processes related to immune cell functions. JAK2 and JAK3 are associated with the pathogenesis of leukemia and common lymphoid-derived illnesses. JAK2/3 inhibitors could reduce the risk of various diseases by targeting this pathway. Herein, the naphthoquinones were experimentally and theoretically investigated to identify novel JAK2/3 inhibitors. Napabucasin and 2'-methyl napabucasin exhibited potent cell growth inhibition in TF1 (IC₅₀ = 9.57 and 18.10 μM) and HEL (IC₅₀ = 3.31 and 6.65 μM) erythroleukemia cell lines, and they significantly inhibited JAK2/3 kinase activity (in a nanomolar range) better than the known JAK inhibitor, tofacitinib. Flow cytometric analysis revealed that these two compounds induced apoptosis in TF1 cells in a time and dose-dependent manner. From the molecular dynamics study, both compounds formed hydrogen bonds with Y931 and L932 residues and hydrophobically contacted with the conserved hinge region, G loop, and catalytic loop of the JAK2. Our obtained results suggested that napabucasin and its methylated analog were potential candidates for further development of novel anticancer drug targeting JAKs.

Novel mechanism of napabucasin, a naturally derived furanonaphthoquinone: apoptosis and autophagy induction in lung cancer cells through direct targeting on Akt/mTOR proteins

Background

Akt and mTOR are aberrantly activated in cancers and targeting these proteins are interesting for cancer drug discovery. Napabucasin (NB), a phytochemical compound, has been reported as potential anti-cancer agent, however, Akt and mTOR targeting mechanisms remain unclear. 

Method

Apoptosis induction was investigated by Hoechst 33342/PI double staining and annexin V/PI staining with flowcytometry. Autophagy was evaluated by monodansylcadaverine staining and Western blot analysis. Binding affinity of NB and essential signaling proteins (PI3K, Akt, and mTOR) was investigated using molecular docking and confirmed by Western blot analysis.

Result

A structure modification from changing methyl moiety of acetyl group of NB to hydroxyl moiety of carboxyl group of NB derivative (napabucasin-acid or NB-acid) greatly affected the compound activities. NB showed more potent anti-cancer activity. NB reduced cell viability with an approximately 20 times lower IC₅₀ and inhibited the colony formation capacity much more than NB-acid treated cells. NB induced cell apoptosis, which was accompanied by decrease Bcl‑2 and Mcl-1 and clevage of PARP, while NB-acid show lesser effect on Mcl-1. NB was found to strongly induce autophagy indicated by acidic vesicle staining and the LC3B conversion. Interestingly, computational molecular docking analysis further demonstrated that NB directly bound to Akt and mTOR (complex 1 and 2) proteins at their critical sites indicating that NB targets the upstream regulators of apoptosis and autophagy. The docking results were confirmed by decrease of p-Akt/Akt, p-mTOR/mTOR, and c-Myc a downstream target of Akt protein levels.

Conclusion

Results show for the first time that NB exerts an anti-cancer activity through the direct interaction to Akt and mTOR proteins. The methyl moiety of acetyl group of NB is required for its potent anti-cancer activities. These data encourage further development of NB compounds for Akt and mTOR driven cancers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03727-6.

Homocysteine, Thioretinaco Ozonide, and Oxidative Phosphorylation in Cancer and Aging: A Proposed Clinical Trial Protocol

The objective of the proposed clinical interventional trial is to demonstrate the efficacy of a novel therapeutic strategy in subjects with cancer and hyperhomocysteinemia. Following discovery of abnormal homocysteine thiolactone metabolism in cultured malignant cells, thioretinamide, the amide synthesized from retinoic acid and homocysteine thiolactone, and thioretinaco, the complex formed from cobalamin and thioretinamide, were demonstrated to have antineoplastic, anticarcinogenic, and anti-atherogenic properties in animal models. Retinol, ascorbate, and homocysteine thiolactone are necessary for biosynthesis of thioretinamide and thioretinaco by cystathionine synthase and for formation of thioretinaco ozonide from thioretinamide, cobalamin, and ozone. Thioretinaco ozonide is required for prevention of abnormal oxidative metabolism, aerobic glycolysis, suppressed immunity, and hyperhomocysteinemia in cancer.The pancreatic enzyme therapy of cancer promotes catabolism of proteins, nucleic acids, and glycosaminoglycans with excess homocysteinylated amino groups resulting from abnormal accumulation of homocysteine thiolactone in malignant cells. Dietary deficiencies of pyridoxal, folate, cobalamin, and nitriloside contribute to hyperhomocysteinemia in cancer, and in protein energy malnutrition. A deficiency of dietary sulfur amino acids downregulates cystathionine synthase, causing hyperhomocysteinemia.The organic sulfur compound diallyl trisulfide increases hydrogen sulfide production from homocysteine in animal models, inhibits Stat3 signaling in cancer stem cells, and produces apoptosis of malignant cells. The furanonaphthoquinone compound napabucasin inhibits Stat3 signaling and causes mitochondrial dysfunction, decreased oxidative phosphorylation, and apoptosis of malignant cells. The protocol of the proposed clinical trial in subjects with myelodysplasia consists of thioretinamide and cobalamin as precursors of thioretinaco ozonide, combined with pancreatic enzyme extracts, diallyl trisulfide, napabucasin, nutritional modification to minimize processed foods, vitamin supplements, essential amino acids, and beneficial dietary fats and proteins.

Cytoprotective dihydronaphthalenones from the wood of Catalpa ovata

Three previously undescribed dihydronaphthalenones, 7-hydroxycatalponol, (4S)-3,4-dihydro-4-hydroxy-2-[(2R)-2,3-dihydroxy-3-methylbutylidene]naphthalen-1(2H)-one, and (6S)-5,6-dihydro-6-hydroxy-2,2-dimethyl-2H-benzo[h]chromen-4(3H)-one and one phthalide, (±)-3-(5-hydroxy-5-methyl-2-oxohex-3-en-1-yl)isobenzofuran-1(3H)-one, were isolated from the wood of Catalpa ovata G. Don (Bignoniaceae), together with six known compounds. The structures of the previously undescribed compounds were elucidated by interpretation of 1D and 2D NMR data. The absolute configurations of the dihydronaphthalenones were deduced by analysis of the ECD data and application of Mosher ester methodology. All isolates were investigated for their cytoprotective effects against hydrogen peroxide (H₂O₂)-induced oxidative damage in HepG2 cells. Moreover, the mRNA expression levels of antioxidant enzymes such as heme oxygenase-1 (HO-1) and NAD(P)H:quinine oxidoreductase 1 (NQO1) in HepG2 cells were examined by RT-PCR analysis. As a result, catalponol and epi-catalponol showed antioxidant activities via directly scavenging of intracellular ROS and inducing the antioxidant enzymes in vitro.

Hyperhomocysteinemia, Suppressed Immunity, and Altered Oxidative Metabolism Caused by Pathogenic Microbes in Atherosclerosis and Dementia

Many pathogenic microorganisms have been demonstrated in atherosclerotic plaques and in cerebral plaques in dementia. Hyperhomocysteinemia, which is a risk factor for atherosclerosis and dementia, is caused by dysregulation of methionine metabolism secondary to deficiency of the allosteric regulator, adenosyl methionine. Deficiency of adenosyl methionine results from increased polyamine biosynthesis by infected host cells, causing increased activity of ornithine decarboxylase, decreased nitric oxide and peroxynitrate formation and impaired immune reactions. The down-regulation of oxidative phosphorylation that is observed in aging and dementia is attributed to deficiency of thioretinaco ozonide oxygen complexed with nicotinamide adenine dinucleotide and phosphate, which catalyzes oxidative phosphorylation. Adenosyl methionine biosynthesis is dependent upon thioretinaco ozonide and adenosine triphosphate (ATP), and the deficiency of adenosyl methionine and impaired immune function in aging are attributed to depletion of thioretinaco ozonide from mitochondrial membranes. Allyl sulfides and furanonaphthoquinones protect against oxidative stress and apoptosis by increasing the endogenous production of hydrogen sulfide and by inhibiting electron transfer to the active site of oxidative phosphorylation. Diallyl trisulfide and napabucasin inhibit the signaling by the signal transducer and activator of transcription 3 (Stat3), potentially enhancing immune function by effects on T helper lymphocytes and promotion of apoptosis. Homocysteine promotes endothelial dysfunction and apoptosis by the unfolded protein response and endoplasmic reticulum stress through activation of the N-methyl D-aspartate (NMDA) receptor, causing oxidative stress, calcium influx, apoptosis and endothelial dysfunction. The prevention of atherosclerosis and dementia may be accomplished by a proposed nutritional metabolic homocysteine-lowering protocol which enhances immunity and corrects the altered oxidative metabolism in atherosclerosis and dementia.

Visible-Light-Mediated Remote Aliphatic C-H Functionalizations through a 1,5-Hydrogen Transfer Cascade

A redox-neutral, light-mediated functionalization of unactivated C(sp³ )-H bonds via iminyl radicals is presented here. A 1,5-H transfer followed by the functionalization of a C(sp² )-H bond takes place in aqueous media producing a variety of elaborated fused ketones. Mechanistic investigations have revealed 1,5-H transfer as the reversible, rate-determining step in this transformation. Divergent scaffolds are also accessible via C(sp³ )-N bond formation upon a careful choice of the reaction additives.

Expeditious diastereoselective synthesis of elaborated ketones via remote Csp3-H functionalization

The quest for selective C–H functionalization reactions, able to provide new strategic opportunities for the rapid assembly of molecular complexity, represents a major focus of the chemical community. Examples of non-directed, remote Csp³–H activation to forge complex carbon frameworks remain scarce due to the kinetic stability and thus intrinsic challenge associated to the chemo-, regio- and stereoselective functionalization of aliphatic C–H bonds. Here we describe a radical-mediated, directing-group-free regioselective 1,5-hydrogen transfer of unactivated Csp³–H bonds followed by a second Csp²–H functionalization to produce, with exquisite stereoselectivity, a variety of elaborated fused ketones. This study demonstrates that aliphatic acids can be strategically harnessed as 1,2-diradical synthons and that secondary aliphatic C–H bonds can be engaged in stereoselective C–C bond-forming reactions, highlighting the potential of this protocol for target-oriented natural product and pharmaceutical synthesis.

C-H activation is a powerful method to form functionalised molecules, but is particularly challenging for unactivated sp³ sites. Here the authors report a directing-group-free radical cascade process for converting vinyl azides and carboxylic acids to tetralone derivatives in high diastereoselectivity.

Conversion of lapachol to lomatiol: synthesis of novel naphthoquinone derivatives

The biomimetic synthesis of lomatiol from lapachol and the subsequent transformation of lomatiol to biologically important furano- and pyrano-napthoquinone derivatives have been reported.

Copper-catalyzed intramolecular alkene carboetherification: synthesis of fused-ring and bridged-ring tetrahydrofurans

Fused-ring and bridged-ring tetrahydrofuran scaffolds are found in a number of natural products and biologically active compounds. A new copper-catalyzed intramolecular carboetherification of alkenes for the synthesis of bicyclic tetrahydrofurans is reported herein. The reaction involves Cu-catalyzed intramolecular addition of alcohols to unactivated alkenes and subsequent aryl C-H functionalization provides the C-C bond. Mechanistic studies indicate a primary carbon radical intermediate is involved and radical addition to the aryl ring is the likely C-C bond-forming mechanism. Preliminary catalytic enantioselective reactions are promising (up to 75% ee) and provide evidence that copper is involved in the alkene addition step, likely through a cis-oxycupration mechanism. Catalytic enantioselective alkene carboetherification reactions are rare and future development of this new method into a highly enantioselective process is promising. During the course of the mechanistic studies a protocol for alkene hydroetherification was also developed.

Semisynthesis and antitumoral activity of 2-acetylfuranonaphthoquinone and other naphthoquinone derivatives from lapachol

Ozonolysis of lapachol (1), resulting in an unusual formation of a potent antitumor agent 2-acetylfuranonaphthoquinone (3) along with the expected aldehyde 6, is described. The reaction of lapachol (1) with CAN in dry acetonitrile leading to biologically active furanonaphthoquinones is also reported. The antitumoral activity of the tested compounds on human DU-145 prostate carcinoma cells was evaluated following XTT assay. The results revealed that 2-(1-methylethenyl)-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (5), beta-lapachone (10) and dehydro-beta-lapachone diacetate (11) showed 100% inhibition at 25 microg/ml. All the tested samples showed dose-dependent activity.

Relationships between inhibitory activity against a cancer cell line panel, profiles of plants collected, and compound classes isolated in an anticancer drug discovery project

In an attempt to determine the relationships between the plant profiles (country of collection, taxonomy, plant part) and the compound classes isolated with cytotoxic activity against a panel of human tumor cell lines, the data compiled from a 15-year anticancer drug-discovery project were subjected to an analysis of variance (ANOVA). The results indicate significant trends in cytotoxic activity relative to collection location, taxonomy, plant part, and compound classes isolated. Plant collections were made in tropical forests in six countries, with collections from Ecuador resulting in higher activity than those from Indonesia and Peru. Interestingly, collections from Florida were not statistically different than those from the countries with higher biodiversity. One hundred and forty-five families were represented in the collections, with the Clusiaceae, Elaeocarpaceae, Meliaceae, and Rubiaceae having low ED50 (half maximal effective dose) values. Especially active genera included Aglaia, Casearia, Exostema, Mallotus, and Trichosanthes. Roots and below-ground plant materials were significantly more active than above-ground materials. Cucurbitacins, flavaglines, anthraquinones, fatty acids, tropane alkaloids, lignans, and sesquiterpenoids were significantly more active than xanthones and oligorhamnosides. The results from this study should serve as a guide for future plant collection endeavors for anticancer drug discovery.

The Chemical Constituents of the FungusStereum sp

Four new compounds, including a sesquiterpene and three aromatic compounds, and a known compound were isolated from a culture broth of the fungus Stereum sp. The novel sesquiterpene was determined to be stereumone A ((+)-2,3,4a,5,6,7,8a,9-octahydro-5-hydroxy-6,6,9-trimethyl-4,8a-epoxynaphtho[2,3-b]furan-8(8H)-one; 1), and the three new aromatic compounds were elucidated as 3,5-dihydroxy-4-(3-methylbut-2-enyl)benzene-1,2-dicarbaldehyde (2), 5,7-dihydroxy-6-(3-methylbut-2-enyl)isobenzofuran-1(3H)-one (3), butyl 2,4-dihydroxy-6-methylbenzoate (4), together with the known compound methyl 2,4-dihydroxy-6-methylbenzoate (5). The structures were established by spectroscopic methods including 2D-NMR techniques. Compounds 2 and 4 showed evident nematicidal activity against nematode Panagrellus redivivus.