Peganumine A, a β-carboline dimer with a new octacyclic scaffold from Peganum harmala

A new polyketide glycoside from the rhizospheric Clonostachys rogersoniana associated with Panax notoginseng

A new polyketide glycoside rogerson A (1), along with two known compounds, rogerson B (2) and (22E)-5α,8α-epidioxyergosta-6,22-dien-3β-ol (3), was obtained from the solid fermentation of Clonostachys rogersoniana, which was isolated from the rhizosphere soil of Panax notoginseng. Rogerson B (2) was isolated for the first time from a natural source. Their structure was determined by extensive analyses of NMR and MS studies. Compounds 1 and 2 were tested for its cytotoxicity against five human cancer cell lines.

Antiproliferative Dimeric Aporphinoid Alkaloids from the Roots of Thalictrum cultratum

Inspired by the intriguing structures and bioactivities of dimeric alkaloids, 11 new thalifaberine-type aporphine-benzylisoquinoline alkaloids, thalicultratines A-K, a tetrahydroprotoberberine-aporphine alkaloid, thalicultratine L, and five known ones were isolated from the roots of Thalictrum cultratum. Their structures were defined on the basis of NMR and HRESIMS data. The antiproliferative activities of compounds 1-17 were evaluated against human leukemia HL-60 and prostate cancer PC-3 cells. Most alkaloids showed potent cytotoxicity against selected cancer cells. Preliminary SARs are discussed. The most active new compound (3), with an IC₅₀ value of 1.06 μM against HL-60 cells, was selected for mechanism of action studies. The results revealed that compound 3 induced apoptosis and arrested the HL-60 cell cycle at the S phase with the loss of mitochondria membrane potential. The nuclear morphological Hoechst 33258 staining assay was also carried out, and the results confirmed apoptosis.

Muscarine, imidazole, oxazole and thiazole alkaloids

Covering: July 2012 to June 2015. Previous review: Nat. Prod. Rep., 2013, 30, 869-915The structurally diverse imidazole-, oxazole-, and thiazole-containing secondary metabolites are widely distributed in terrestrial and marine environments, and exhibit extensive pharmacological activities. In this review the latest progress involving the isolation, biological activities, and chemical and biogenetic synthesis studies on these natural products has been summarized.

A review on traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology of the genus Peganum

ETHNOPHARMACOLOGICAL RELEVANCE

The plants of the genus Peganum have a long history as a Chinese traditional medicine for the treatment of cough, hypertension, diabetes, asthma, jaundice, colic, lumbago, and many other human ailments. Additionally, the plants can be used as an amulet against evil-eye, dye and so on, which have become increasingly popular in Asia, Iran, Northwest India, and North Africa.

AIM OF THE REVIEW

The present paper reviewed the ethnopharmacology, phytochemistry, analytical methods, biological activities, metabolism, pharmacokinetics, toxicology, and drug interaction of the genus Peganum in order to assess the ethnopharmacological use and to explore therapeutic potentials and future opportunities for research.

MATERIALS AND METHODS

Information on studies of the genus Peganum was gathered via the Internet (using Google Scholar, Baidu Scholar, Elsevier, ACS, Pudmed, Web of Science, CNKI and EMBASE) and libraries. Additionally, information was also obtained from some local books, PhD and MS's dissertations.

RESULTS

The genus Peganum has played an important role in traditional Chinese medicine. The main bioactive metabolites of the genus include alkaloids, flavonoids, volatile oils, etc. Scientific studies on extracts and formulations revealed a wide range of pharmacological activities, such as cholinesterase and monoamine oxidase inhibitory activities, antitumor, anti-hypertension, anticoagulant, antidiabetic, antimicrobial, insecticidal, antiparasidal, anti-leishmaniasis, antioxidant, and anti-inflammatory.

CONCLUSIONS

Based on this review, there is some evidence for extracts' pharmacological effects on Alzheimer's and Parkinson's diseases, cancer, diabetes, hypertension. Some indications from ethnomedicine have been confirmed by pharmacological effects, such as the cholinesterase, monoamine oxidase and DNA topoisomerase inhibitory activities, hypoglycemic and vasodilation effects of this genus. The available literature showed that most of the activities of the genus Peganum can be attributed to the active alkaloids. Data regarding many aspects of the genus such as mechanisms of actions, metabolism, pharmacokinetics, toxicology, potential drug interactions with standard-of-care medications is still limited which call for additional studies particularly in humans. Further assessments and clinical trials should be performed before it can be integrated into medicinal practices.

Recent progress in organocatalytic asymmetric total syntheses of complex indole alkaloids

Indole and its structural analogues have been frequently found in numerous alkaloids, pharmaceutical products and related materials. The enantioselective construction of these structures allows efficient total synthesis of optically pure indole alkaloids, and hence has received worldwide interest. In the past decade, asymmetric organocatalysis has been recognized as one of the most powerful strategies to create chiral molecules with high levels of stereoselectivity. In particular, organocatalytic asymmetric cascade reactions often occur with multiple bond-breaking and forming events simultaneously or sequentially, leading to the appearance of various straightforward approaches to access core structures for asymmetric total synthesis. This review will summarize recent applications of asymmetric organocatalysis in the enantioselective synthesis of indole alkaloids.

Structurally Diverse Alkaloids from the Seeds of Peganum harmala

Investigation of the alkaloids from Peganum harmala seeds yielded two pairs of unique racemic pyrroloindole alkaloids, (±)-peganines A-B (1-2); two rare thiazole derivatives, peganumals A-B (3-4); six new β-carboline alkaloids, pegaharmines F-K (5-10); and 12 known analogues. Their structures, including stereochemistry, were elucidated through spectroscopic analyses, quantum chemistry calculations, and single-crystal X-ray diffraction. Notably, the incorporation of pyrrole and indole moieties in peganines A-B, thiazole fragments in peganumals A-B, and a C-1 α,β-unsaturated ester motif in pegaharmine F (5) are all rare, and their presence in the genus Peganum were demonstrated for the first time. All isolates were tested for antiproliferative activities against the HL-60, PC-3, and SGC-7901 cancer cell lines, and compounds 9, 11, 12, and 13 exhibited moderate cytotoxicity against HL-60 cancer cell lines with IC₅₀ values in the range of 4.36-9.25 μM.

Fermentation of Illigera aromatica with Clonostachys rogersoniana producing novel cytotoxic menthane-type monoterpenoid dimers

Five novel menthane-type monoterpenoid dimers were isolated from non-fermented and Clonostachys rogersoniana fermented Illigera aromatica.

In(OTf)3 assisted synthesis of β-carboline C-3 tethered imidazo[1,2-a]azine derivatives

Synthesis of β-carboline based natural products and synthetic derivatives is one of the frontier areas of research owing to their medicinal properties.

Bioactive benzofuran-chalcanes as potential NQO1 inducers from Millettia pulchra (Benth) kurzvar-laxior (Dunn) Z.Wei

Five chalcanes ((α'R)-2, α'-dimethoxy-furano-[4″, 5'': 3', 4'] chalcane, (α'R, βR)-2', α', β-trimethoxy-furano-[4″, 5'': 3', 4'] chalcane, (α'S, βR)-2', α', β-trimethoxy-furano-[4″, 5'': 3', 4'] chalcane, (α'R, βR)-2', β-dimethoxy-α'-hydroxyethoxy-furano-[4″, 5'': 3', 4'] chalcane, (α'S, βR)-2', β-dimethoxy-α'-hydroxyethoxy-furano-[4″, 5'': 3', 4'] chalcane) and a flavonoid glycoside (3', 7-dihydroxy-6-methoxy-4', 5'-methylenedioxyisoflavone 6-O-β-D- glucopyranoside), together with 15 known components, were isolated from the leaves of Millettia pulchra (Benth) Kurzvar-laxior (Dunn) Z. Wei, a traditional Zhuang medicine. Their chemical structures were established by extensive analysis of NMR, mass spectrometry and ECD spectra. Furthermore compounds (α'R, βR)-2', β-dimethoxy-α'-hydroxyethoxy-furano-[4″, 5'': 3', 4'] chalcane, (α'S, βR)-2', β-dimethoxy-α'-hydroxyethoxy-furano-[4″, 5'': 3', 4'] chalcane, quercetin, methyl 2-O-β-D-glucopyranosylbenzoate, 6,7-dimethoxy-3',4'-methylenedioxyisoflavone and lyoniresinol were suggested to be potential chemopreventive agents because of their significant activity in inducing NQO1 ([NAD(P)H quinine oxidoreductase 1], a phase II metabolism enzyme).

Three New Butenolides from the Fungus Aspergillus sp. CBS-P-2

Three new butenolides aspernolides H–J (1–3) together with seven known ones (4–10) were isolated from the fungus Aspergillus sp. CBS-P-2. Their chemical structures were established on the basis of 1D- and 2D-NMR spectroscopic data, HR-ESI-MS analysis, and their absolute configuration were determined by circular dichroism (CD) analysis. All the compounds were evaluated for the antioxidant effects by DPPH and ABTS methods, the antitumor activities against four human tumor cell lines (HL-60, ASPC1, HCT-116 and PC-3) and antimicrobial activities. Compounds 4–10 showed significant activity against DPPH (IC₅₀ = 15.9–34.3 μM) and compounds 1–10 exhibited significant ABTS free radical scavenging activity (IC₅₀ = 2.8–33.1 μM). Compounds 2, 5 and 11 showed potent cytotoxic activities against HL-60 cell lines with IC₅₀ values of 39.4, 13.2 and 16.3 μM, respectively. Compound 10 showed good antimicrobial activity against Staphylococcus aureus with minimum inhibitory concentration (MIC) of 21.3 μM.

Enantioselective Synthesis of (+)-Peganumine A

A gram-scale enantioselective total synthesis of (+)-peganumine A was accomplished in 7 steps from commercially available 6-methoxytryptamine. Key steps included (a) a Liebeskind-Srogl cross-coupling; (b) a one-pot construction of the tetracyclic skeleton from an ω-isocyano-γ-oxo-aldehyde via a sequence of an unprecedented C-C bond forming lactamization and a transannular condensation; (c) a one-pot organocatalytic process merging two achiral building blocks into an octacyclic structure via a sequence of enantioselective Pictet-Spengler reaction followed by a transannular cyclization. This last reaction created two spirocycles and a 2,7-diazabicyclo[2.2.1]heptan-3-one unit with excellent control of both the absolute and relative stereochemistry of the two newly created quaternary stereocenters.

A Series of β-Carboline Alkaloids from the Seeds of Peganum harmala Show G-Quadruplex Interactions

In this study, we screened 17 medicinal plants for binding activity to G-quadruplex d(TTGGGTT)4 by (1)H NMR spectroscopy and found that the crude extract of Peganum harmala L. seeds showed the most potential binding activity. Subsequently, (1)H NMR- and bioassay-guided isolation of the extract of P. harmala L. was performed to obtain four pairs of partially racemized β-carboline alkaloids, pegaharmines A-D (1-4). Their structures and absolute configurations were determined by extensive NMR analyses, X-ray crystallography, ECD calculations, and CD exciton chirality approaches. Interestingly, pegaharmine D (4), which showed the strongest G-quadruplex interaction, exhibited significant cytotoxic activity against three cancer cell lines. This work contributed a practical strategy for the discovery of novel G-quadruplex ligands from natural products and provided potential insights for using β-carboline alkaloids as anticancer lead compounds specifically targeting G-quadruplexes.

Synthesis, Biological Activity, and Apoptotic Properties of NO-Donor/Enmein-Type ent-Kauranoid Hybrids

Herein, we reported on a series of synthetic nitric oxide-releasing enmein-type diterpenoid hybrids (9a–i). All the target compounds showed potent antibacterial activity against selected Gram-positive bacteria S. aureus and B. subtilis. The antiproliferative activity against human tumor K562, MGC-803, CaEs-17 and Bel-7402 cells, and human normal liver cells L-02 was tested and the structure activity relationships (SARs) were also concluded. Compounds 9b and 9d showed the best activity against S. aureus and B. subtilis with the same minimal inhibitory concentrations (MICs) of 4 and 2 μg/mL, respectively. The derivative 9f displayed IC₅₀ values of 1.68, 1.11, 3.60 and 0.72 μM against the four cancer cell lines above and 18.80 μM against normal liver cells L-02; meanwhile, 9f also released a high level of NO at the time point of 60 min of 22.24 μmol/L. Furthermore, it was also found that 9f induced apoptosis via the mitochondria-related pathway and arrested cell cycle of Bel-7402 cells at S phase. These findings might be important to explore new chemical entities for the main causes of in-hospital mortality of S. aureus infection, combined with a solid tumor.

Synthesis of S-(-)-5,6-Dihydrocanthin-4-ones via a Triple Cooperative Catalysis-Mediated Domino Reaction

An enantioselective synthesis of S-(-)-5,6-dihydrocanthin-4-ones via a triple cooperative catalysis-mediated domino reaction having a broad substrate scope is reported. The reaction between substituted 1-formyl-9H-β-carbolines and terminal alkynes in the presence of catalytic amounts of Jorgensen-Hayashi catalyst, copper iodide, and Hunig base proceeded via a multicascade route, affording the title compounds in good yields and excellent ees with interesting mechanistic features. These compounds were assessed for in vitro antiplasmodial activity against P. falciparum strains. Additionally, 5,6-dihydrocanthin-4-ones are demonstrated to be a versatile precursor to different fused β-carboline derivatives via simple synthetic transformations.

Concise total synthesis of water soluble metatacarboline A, C, D, E and F and its anticancer activity

The simple, concise, protecting group free and first total synthesis of Metatacarboline alkaloids (abbreviated as Mc) Mc A, C, D, E and F are reported. The core structure of metatacarboline alkaloids has been constructed by the classical Wittig reaction as key step from easily accessible starting materials with 40-75% overall yields. These synthesized compounds have been subjected to evaluate for their anticancer activity using C6 glioma cell lines. Mc D and Mc F showed significant antiproliferative activity, which was confirmed by MTT and Clonogenic assay. FACS analysis showed that Mc D and Mc F arrested the cell cycle at sub G0/G1 and G2/M phase of cell cycle respectively. Further, Western blot analysis and immunohistochemistry of Mc D treated cells revealed activation of caspase dependent downstream signaling which led to apoptosis.

Synthesis and biological evaluation of bivalent β-carbolines as potential anticancer agents

A series of novel bivalent β-carbolines were synthesized and evaluated for their anti-proliferative activities on a panel of cancer cell lines, apoptosis induction and cell cycle effects.

Peganumine B-I and two enantiomers: new alkaloids from the seeds of Peganum harmala Linn. and their potential cytotoxicity and cholinesterase inhibitory activities

Ten new alkaloids (peganumine B-I and two enantiomers), containing five β-carbolines, three quinazolones, two compounds with both of the above skeletons, and one amphoteric alkaloid with a four-membered ring, were isolated from Peganum harmala.

Absolute Configurations and NO Inhibitory Activities of Terpenoids from Curcuma longa

Curcuma longa L., belonging to the Zingiberaceae family, is a perennial herb and has been used as a spice and a pigment in the food industry. In the ongoing search for inhibitory reagents of NO production and survey of the chemical composition of natural vegetable foods, the chemical constituents of C. longa used as spice were investigated. This investigation resulted in the isolation of 2 new terpenoids and 14 known analogues. Their structures were established on the basis of the extensive analyses of 1D and 2D NMR spectroscopic data, and the absolute configurations of 1-4 were elucidated by comparison of the calculated and experimental ECD spectra. Among them, compound 1 is a rare norditerpene with an ent-labdane skeleton, and 2 is a skeletally novel sesquiterpene having an eight-membered ring. All of the compounds were found to possess NO inhibitory activities in murine microglial BV-2 cells. The discovery of two new compounds in this chemical investigation further disclosed the chemical composition of C. longa used a food spice, and the bioassay implied that the natural food spice C. longa, containing terpenoids with NO inhibitory activities, may be potentially promotive to human health.

MCR synthesis of a tetracyclic tetrazole scaffold

Scaffold diversity is key in the ongoing exercise of discovery of novel bioactive compounds using high throughput screening (HTS). Based on the Ugi tetrazole synthesis we have designed novel bi- and tri-cyclic scaffolds featuring interesting pharmacophore properties. The compounds of the scaffold (B) are synthesizable in large diversity and numbers in two steps using (hetero)phenylethylamines, HN3, oxo components and iscyanoacetaldehyde(dimethylacetale). The chemistry is amenable to parallel synthesis and is used to enhance and fill the screening decks of the European Lead factory (ELF). Here, we are reporting full experimental details, scope and limitations of the reaction, cheminformatic analysis and the 3D structures of selected compounds.

Two Unusual Polycyclic Polyprenylated Acylphloroglucinols, Including a Pair of Enantiomers from Garcinia multiflora

Two polycyclic polyprenylated acylphloroglucinols, garcimulins A and B ((±)-1 and 2), including a pair of enantiomers with the unique caged tetracyclo[5.4.1.1(1,5).0(9,13)]tridecane skeleton were isolated from Garcinia multiflora. Their structures and absolute configurations were determined by extensive analysis of spectroscopic data and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 exhibited cytotoxic activities against five human cancer cell lines in vitro (IC50 3.42-13.23 μM). The acidification of lysosomes in HeLa cell was obviously affected by compound 2.