Terpenoids from Turraeanthus species

Chemical investigation of the root bark of Turraeanthus mannii and the stem of T. longipes resulted in the isolation of two new diterpenes, 13-methyl-labda-8(17)-en-15-oic acid (1) and 13-(hydroxymethyl)-14-hydroxy-ent-labda-8(17)-en-15-oic acid (2), along with two known diterpenes, 19-hydroxy-ent-labda-8(17),13-dien-15,16-olide (3) and 19-acetoxy-ent-labda-8(17),13-dien-15,16-olide (4), and the phytosterol, stigmasterol. The structure elucidation of the new compounds has been achieved using spectroscopic techniques.     

Atropo-enantioselective total synthesis of knipholone and related antiplasmodial phenylanthraquinones

The "lactone concept" has been efficiently employed for the first atropo-enantioselective synthesis of knipholone and related natural phenylanthraquinones. Besides the regio- and stereoselective construction of the biaryl axis, another important step was the "synthetically late" introduction of the C-acetyl group, either by a Friedel-Crafts type acetylation or by an ortho-selective Fries rearrangement first tested on simplified model systems and subsequently applied to the highly atroposelective preparation of the natural products and of simplified analogs thereof for biotesting. The synthetic availability of these natural biaryls, their precursors, and their unnatural analogs permitted a broader investigation of the antiplasmodial activities of these interesting biaryls.     

Epunctanone,a New Benzophenone,and Further Secondary Metabolites from Garcinia epunctata Stapf (Guttiferae)

A new polyprenylated benzophenone, named epunctanone ( 1 ), was isolated from the stem bark of Garcinia epunctata Stapf , together with eight known compounds, 7‐epiisogarcinol ( 2 ), 2,6‐dimethoxy‐p‐benzoquinone ( 3 ), friedelin ( 4 ), lupeol ( 5 ), 16β‐hydroxylupeol ( 6 ), betulin ( 7 ), stigmasterol ( 8 ), and rheediaxanthone A ( 9 ). The structure of epunctanone ( 1 ) was established by detailed analysis of its spectroscopic data, especially 1D‐ and 2D‐NMR, and HR‐MS data. All these compounds were evaluated for their antimicrobial and anti‐protozoan activities. They were also assayed to determine if any of the compounds were nonpeptide agonist ligands for nematodal G‐protein‐coupled receptors, which would be an indication of potential antinematodal activity. Among the isolated compounds, 7‐epiisogarcinol ( 2 ) was the most active against Candida albicans.     

The discretized flow on domains of attraction: a structural stability result

It is well known that, for stepsize sufficiently small, compactattractors of ordinary differential equations persist underdiscretization. The present paper describes the structure ofthe discrete-time dynamical system obtained via discretizationon A(M_h)\M_h where M_h is the approximate attractor and A(M_h)is its domain of attraction. The existence of a smooth embeddinginto a continuous-time parallelizable flow is proved. The constructioncan be used to define sections for discretizations and can beinterpreted as a justification of the method of modified equations.     

THE CHEMISTRY OF 3-AMINOTHIOACRYLAMIDES; PART II: 3-AMINOTHIOACRYLAMIDES AS USEFUL SYNTHONS IN ORGANIC SYNTHESIS

Abstract

3-Aminothioacrylamides are a class of organic sulfur containing compounds that are easily available and exhibit polyfunctional reaction behaviour. They can be used widely in the synthesis of a variety of heterocyclic and open chain compounds. The synthetic utility of 3-aminothioacrylamides can be further extended if additional functionalities are incorporated.     

Donellanic acids A–C: new cyclopropanic oleanane derivatives from Donella ubanguiensis (Sapotaceae)

Three new cyclopropanic oleanane triterpenoids and ten known compounds were obtained from Donella ubanguiensis using chromatographic methods. The structures were established on the basis of mass spectrometric and NMR data and by comparison with values reported in the literature. The structures of the new compounds were confirmed by X-ray crystallography. A part of the isolated compounds was evaluated for cytotoxic and antimicrobial activities.     

Duboscic acid: a potent α-glucosidase inhibitor with an unprecedented triterpenoidal carbon skeleton from Duboscia macrocarpa

Duboscic acid (1), a triterpenoid with a unique carbon backbone, was isolated from Duboscia macrocarpa Bocq. It is the first member of a new class of triterpenoids, for which the name "dubosane" is proposed. Duboscic acid has a potent α-glucosidase inhibition, and its structure was unambiguously deduced by a single-crystal X-ray diffraction study.     

Isolation and characterisation of novel antioxidant constituents of Croton zambesicus leaf extract

A 1,1-diphenyl-2-picrylhydrazyl (DPPH)-activity-directed fractionation was used to target antioxidant constituents of the ethyl acetate fraction obtained from a 20% aqueous methanol crude extract of Croton zambesicus leaf. Repeated column chromatography of the fraction on silica gel and Sephadex LH-20 led to the isolation of a new natural product, identified as quercetin-3-O-β-6″(p-coumaroyl) glucopyranoside-3'-methyl ether, helichrysoside-3'-methyl ether (1), along with kaempferol-3-O-β-6″(p-coumaroyl) glucopyranoside, tiliroside (2) and apigenin-6-C-glucoside, isovitexin (3) as the antioxidant constituents. The structures of the isolated compounds were elucidated using spectroscopic techniques, namely NMR (1D and 2D) and mass spectrometry. Compounds 1 and 2 are reported from this species for the first time. In the qualitative antioxidant assay, the three isolated compounds instantly bleached the DPPH (0.2% MeOH) purple colour indicating antioxidant activity. In the quantitative antioxidant assay, all the isolated compounds demonstrated weak antioxidant activity compared to quercetin and rutin used as positive control antioxidant agents. The compounds displayed little to no cytotoxicity against Vero cells in an in?vitro assay. The presence of these antioxidant compounds in the leaf extract of C. zambesicus could provide a rationale for the ethnomedicinal use of the plant in the management of oxidative-stress-related diseases in folk medicine.     

Non‐Anticoagulant Heparin Prodrug Loaded Biodegradable and Injectable Thermoresponsive Hydrogels for Enhanced Anti‐Metastasis Therapy

Metastasis is a pathogenic spread of cancer cells from the primary site to surrounding tissues and distant organs, making it one of the primary challenges for effective cancer treatment and the major cause of cancer mortality. Heparin‐based biomaterials exhibit significant inhibition of cancer cell metastasis. In this study, a non‐anticoagulate heparin prodrug is developed for metastasis treatment with a localized treatment system using temperature sensitive, injectable, and biodegradable (poly‐(ε‐caprolactone‐co‐lactide)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone‐co‐lactide) polymeric hydrogel. The drug molecule (heparin) is conjugated with the polymer via esterification, and its sustained release is ensured by hydrolysis and polymeric biodegradation. An aqueous solution of the polymer could be used as an injectable solution at below 25 °C and it achieves gel formation at 37 °C. The anti‐metastasis effect of the hydrogels is investigated both in vitro and in vivo. The results demonstrated that local administration of injectable heparin‐loaded hydrogels effectively promote an inhibitory effect on cancer metastasis.