A Rhodamine-coumarin Triazole Conjugate as a Fluorescent Chemodosimeter for Cu(II) Detection and its Application in Live Cell Bioimaging.

A rhodamine-triazole fluorescent probe bearing a coumarin moiety RTC was synthesized using the Cu(I)-catalyzed click reaction. The rhodamine-triazole conjugate was highly selective to Cu2+ among other metal ions, including Ca2+, Co2+, Cu2+, Cd2+, Mg2+, Fe2+, Fe3+, Hg2+, Zn2+, Ni2+, Pd2+ and Pb2+ in physiological conditions. Upon the addition of Cu2+, the colorless RTC solution turned pink and exhibited a significant fluorescence emission centered at 578 nm. The binding of Cu2+ induced a hydrolysis reaction, leading to a release of the coumarin unit from the rhodamine probe, as confirmed by mass spectrometric data. From the fluorescence titration, the detection limit of RTC for Cu2+ was determined to be 21 nM (1.3 ppb). The sensor was responsive to Cu2+ in a wide pH range and successfully applied to monitor Cu2+ in HEK293T cells by confocal fluorescence imaging.

A Rhodamine-based Fluorescent Chemodosimeter for Au3+ in Aqueous Solution and Living Cells.

A highly selective rhodamine hydrazide-based fluorescent chemosensor for Au3+ detection was developed. The aqueous solution of rhodamine N-hydroxysemicarbazide (RHS), in the presence of Au3+, exhibited a significant 55-fold turn-on fluorescence response at 591 nm and a colorimetric change from colorless to pink. Other interested ions including Li+, Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Pb2+, Mn2+, Co2+, Ni2+, Ag+, Cd2+, Cu2+, Hg2+, Zn2+, Sn2+, Fe2+, Fe3+, Cr3+, Ce3+ did not induce any distinct color/spectral changes. The irreversible detection mechanism occurred via Au3+-promoted 5-exo-trig ring closure to yield 1,3,4-oxadiazole-2-one product. The RHS probe is non-responsive to other biologically relevant metal ions and the limit of detection for Au3+ was calculated to be 0.5 µM with a linear range of 0 to 90 µM. Fluorescence bioimaging of Au3+ in HepG2 cells was also successfully demonstrated.

A rhodamine-triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging.

A rhodamine-based fluorescent chemodosimeter rhodamine hydrazide-triazole (RHT) tethered with a triazole moiety was developed for Cu2+ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu2+ among other metal ions. The addition of Cu2+ triggered a fluorescence emission of RHT by 384-fold (Φ = 0.33) based on a ring-opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu2+ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu2+ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu2+ in Chang liver cells by confocal fluorescence microscopy.

Anti-inflammatory 12,20-Epoxypregnane and 11,12-seco-Pregnane Glycosides from the Stems of Hoya kerrii.

Five 12,20-epoxypregnane glycosides (1-3, 5, and 6) and two 11,12-seco-pregnane glycosides (4 and 7) with spirodilactone motifs, as well as spirodilactone cleavage products 8 and 9, were isolated from the stems of Hoya kerrii. The relative configurations of the three related skeletons were supported by ROESY experiments and X-ray crystallographic analyses. The isolates were evaluated for their anti-inflammatory activity based on the inhibition of NO production in RAW264.7 cells, and some showed IC50 values ranging from 12.6 to 96.5 µM. The most potent compound, 9a, was also examined for its anti-inflammatory mechanism against mRNA expression and was found to down-regulate mRNA expression of iNOS and COX-2 in a dose-dependent manner.

Cytotoxic lanostanes from fruits of Garcinia wallichii Choisy (Guttiferae).

Five new lanostanes, wallichinanes A-E (1-5) together with a known lanostane derivative 6 were isolated from the cytotoxic hexanes extract of fruits of Garcinia wallichii Choisy (Guttiferae). The structures of the isolated compounds were established by analysis of spectroscopic data, X-ray diffraction technique as well as comparison with the literature data. The cytotoxicity of all isolated compounds against a panel of cultured cancer cell lines was evaluated. Compound 4 exhibited good cytotoxicity with ED50 values ranging from 3.91 to 7.63µM.

F-THENA: a chiral derivatizing agent for the determination of the absolute configuration of secondary aromatic alcohols with a self-validating system.

F-THENA is designed as an alternative fluorine-containing chiral derivatizing agent (CDA). The fluorine atom functions exclusively as a reporter which can directly sense an anisotropic effect from an aromatic substituent of a chiral alcohol. In combination with chemical shift differences from both 19F NMR and 1H NMR, the F-THENA method can successfully be used for determining the absolute configuration of chiral secondary aromatic alcohols with a self-validating system.

Triterpene lactones from cultures of Ganoderma sp. KM01.

A revised structure of colossolactone G (1), seven new triterpene lactones, ganodermalactones A-G (2-8), and five known triterpene lactones, colossolactone I (9), schisanlactone B (10), colossolactone B (11), colossolactone E (12), and colossolactone IV (13), and ergosterol have been isolated from cultured biomass of the macrofungi Ganoderma sp. KM01. Their structures were identified by spectroscopic methods. Structures and relative configurations of 3, 7, and 8 were confirmed by X-ray crystallographic analysis. Compounds 7, 10, and 12 exhibited antimalarial activity against Plasmodium falciparum in the range 6.0-10.0 µM (IC50).

A highly sensitive and selective rhodamine-semicarbazide based fluorescent sensor for Cu2+ detection in real water samples and fluorescence bioimaging in HepG2 cells.

A colorimetric and fluorescent sensor, selective for Cu2+ ions, was synthesized in two steps using a rhodamine-based compound attached to the semicarbazide-picolylamine moiety (RBP). Spectroscopic measurements, including UV-Vis absorption and fluorescence emission, were conducted in the semi-aqueous medium containing acetonitrile/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, denoted as MeCN/HEPES buffer (2:8, v/v, pH 7.0). The sensor exhibited high selectivity towards Cu2+ ions compared to other cations and demonstrated remarkable sensitivity towards Cu2+ ions, with a limit of detection at the nanomolar level. The calculated transitions indicated a 1:1 stoichiometric binding of RBP to Cu2+ ions based on a 4-coordination mode involving additional chelation in the semi-aqueous medium. The sensing mechanism for the detection of Cu2+ ions was investigated using high-resolution mass spectroscopy. The sensor could be employed as a real-time chemosensor for monitoring Cu2+ ions. Furthermore, the sensor has the potential for utilization in the detection of Cu2+ ions in actual water samples with the high precision and accuracy, as indicated by the small relative standard derivation values. The 50th percentile cytotoxicity concentration of RBP was found to be 22.92 µM. Additionally, the fluorescence bioimaging capability of RBP was demonstrated for the detection of Cu2+ ions in human hepatocellular carcinoma (HepG2) cells.

Regioselectivity of Larock heteroannulation: a contribution from electronic properties of diarylacetylenes.

A series of 2,3-diarylindoles were synthesized from 2-iodoaniline and unsymmetrical diarylacetylenes using the Larock heteroannulation. Diarylacetylenes bearing electron-withdrawing substituents lead to 2,3-diarylindoles with substituted phenyl moieties at the 2-position as major products, while those with electron-donating groups preferably yield indole products with substituted phenyl moieties at the 3-position. The regioisomeric product ratios exhibit a clear correlation with Hammett σ(p) values. DFT calculations reveal the origin of this effect, displaying smaller activation energy barriers for those pathways leading to the major regioisomer.

Bridged tricyclic sesquiterpenes from the tubercle nudibranch Phyllidia coelestis Bergh.

A new sesquiterpene, 1-formamido-10(1→2)-abeopupukeanane (1), was isolated from the tubercle nudibranch Phyllidia coelestis Bergh, along with 2-formamidopupukeanane (2), which is reported here as a natural product for the first time. A rearrangement pathway toward the unprecedented tricyclo[4.4.0.0(2,8)]decane skeleton is proposed. Both compounds showed antiproliferative activity when targeting HeLa, MCF-7, KB, and HT-29 cancer cell lines in the range 0.05-10 µM.

Structural and mutational analysis of glycoside hydrolase family 1 Br2 ß-glucosidase derived from bovine rumen metagenome.

Ruminant animals rely on the activities of ß-glucosidases from residential microbes to convert feed fibers into glucose for further metabolic uses. In this report, we determined the structures of Br2, which is a glycoside hydrolase family 1 ß-glucosidase from the bovine rumen metagenome. Br2 folds into a classical (ß/α)8-TIM barrel domain but displays unique structural features at loop ß5→α5 and α-helix 5, resulting in different positive subsites from those of other GH1 enzymes. Br2 exhibited the highest specificity toward laminaritriose, suggesting its involvement in ß-glucan hydrolysis in digested feed. We then substituted the residues at subsites +1 and + 2 of Br2 with those of Halothermothrix orenii ß-glucosidase. The C170E and C221T mutations provided favorable interactions with glucooligosaccharide substrates at subsite +2, while the A219N mutation probably improved the substrate preference for cellobiose and gentiobiose relative to laminaribiose at subsite +1. The N407Y mutation increased the affinity toward cellooligosaccharides. These results give further insights into the molecular determinants responsible for substrate specificity in GH1 ß-glucosidases and may provide a basis for future enzyme engineering applications.

A novel highly selective FRET sensor for Fe(III) and DFT mechanistic evaluation.

A novel FRET-based sensor has been designed and developed through the conjugation of naphthyl and rhodamine via propylamine spacer, Naph-Rh. The naphthyl moiety serves as a FRET donor due to its emission spectrum overlapping with the rhodamine B absorption band. Naph-Rh exhibited a selectivity for sensing Fe3+ over other metal ions with a visual color change and fluorescent enhancement. The ratio of the Naph-Rh and Fe3+ was determined to be 1:1 based on Job's plot analysis with a detection limit of 83 nM. The probe exhibited a linear response to Fe3+ in the range of 0-120 µM. Furthermore, the density functional theory (DFT) calculations of Naph-Rh were carried out to rationalize the design and portray the plausible Fe3+ sensing mechanism.

Asymmetric synthesis of gem-difluoromethylenated dihydroxypyrrolizidines and indolizidines.

An asymmetric synthesis of gem-difluoromethylenated dihydroxypyrrolizidines and indolizidines is described. The fluoride-catalyzed nucleophilic addition of PhSCF(2)SiMe(3) (1) to chiral imides was achieved in satisfactory yields to provide mixtures of syn- and anti-isomers 6-9 with moderate to good diastereoselectivities. Reductive cleavage of the phenylsulfanyl group followed by intramolecular radical cyclization of the syn-isomers 6-9 occurred under refluxing conditions to afford the corresponding gem-difluoromethylenated 1-azabicyclic compounds 10-13 in moderate yields as a separable mixture of cis- and trans-isomers. The cis-isomers of compounds 10 and 12 and trans-13 were readily transformed to gem-difluoromethylenated dihydroxypyrrolizidines 20 and 27 and indolizidine 28, respectively, by reductive cleavage of the hydroxyl group and organometallic addition followed by hydrogenolysis.

Antiplasmodial sesquiterpene alkaloids from the roots of Maytenus mekongensis.

Eight new sesquiterpene alkaloids (1-8) and four known sesquiterpene alkaloids (9-12) have been isolated from the roots of Maytenus mekongensis. Structures were determined using extensive spectroscopic methods. The relative configuration of 7-epi-mekongensine (2) was established by single-crystal X-ray crystallographic analysis. The alkaloids were evaluated for antiplasmodial activity against Plasmodium falciparum, K1 strain, and for cytotoxicity using a panel of cell lines.

Cytotoxic pentacyclic and tetracyclic aromatic sesquiterpenes from Phomopsis archeri.

Three new sesquiterpenes, named phomoarcherins A-C (1-3), and four known compounds, kampanol A (4), R-mevalonolactone, ergosterol, and ergosterol peroxide, were isolated from the endophytic fungus Phomopsis archeri. These structures were established on the basis of spectroscopic evidence. The structure and absolute configuration of 1 were confirmed by X-ray crystallographic analysis of its p-bromobenzoate derivative (1a). Compounds 1-4 showed cytotoxicity against five cholangiocarcinoma cell lines (0.1-19.6 µg/mL), while 1 and 2 exhibited weak cytotoxicity against the KB cell line with IC(50) values of 42.1 and 9.4 µg/mL, respectively. In addition, compound 2 showed antimalarial activity against Plasmodium falciparum with an IC(50) value of 0.79 µg/mL.

Lanostane and hopane triterpenes from the entomopathogenic fungus Hypocrella sp. BCC 14524.

Seven new lanostane-type triterpenes, hypocrellols A-G (1-7), and six new hopane-type triterpenes, 7ß,15α-dihydroxy-22(29)-hopene (8), 3ß,7ß-dihydroxy-22(29)-hopene (9), 3ß-acetoxy-15α-hydroxy-22(29)-hopene (10), 3ß,7ß,15α,22-tetrahydroxyhopane (11), 3ß-acetoxy-7ß,15α,22-trihydroxyhopane (12), and 7ß,15α,22-trihydroxyhopane (13), were isolated from the scale insect pathogenic fungus Hypocrella sp. BCC 14524. The structures of the new compounds were elucidated by analyses of the NMR spectroscopic and mass spectrometry data. The structure of 1 was confirmed by X-ray crystallography.

Bis[2,6-bis-(2-meth-oxy-phen-yl)pyridinium] di-µ-bromido-bis-[dibromidocuprate(II)].

The title salt, (C(19)H(18)NO(2))(2)[Cu(2)Br(6)], was obtained from an attempt to synthesize the copper(II) complex of 2,6-bis-(2-meth-oxy-phen-yl)pyridine (L) from a reaction between CuBr(2) and one equivalent of L in CH(2)Cl(2) at room temperature. The resulting compound is the salt of the 2,6-bis-(2-meth-oxy-phen-yl)pyridinium cation and 0.5 equivalents of a hexa-bromido-dicuprate(II) dianion. Both meth-oxy groups of the cationic pyridinium moiety are directed towards the N atom of the pyridine ring as a result of intra-molecular N-H⋯O hydrogen bonds. The centrosymmetric hexabromidodicuprate dianion possesses a distorted tetra-hedral geometry at the copper ion. The Cu-Br bond lengths are 2.3385 (7) and 2.3304 (7) Šfor the terminal bromides, whereas the bond length between the Cu atom and two bridging bromides is slightly longer [2.4451 (6) Å].

Anti-HIV-1 and anti-inflammatory lupanes from the leaves, twigs, and resin of Garcinia hanburyi.

Two new lupanes, 2 alpha-acetoxy-3 beta-hydroxy-19 beta-hydrogen-lup-20(29)-en-28-oic acid (2-acetoxyalphitolic acid) ( 1) and 2 alpha-hydroxy-3 beta-acetoxy-19 beta-hydrogen-lup-20(29)-en-28-oic acid (3-acetoxyalphitolic acid) ( 2), together with the known betulinic acid ( 3), betulin ( 4), and stimasterol-3- O- beta- D-glucopyranoside ( 5), were isolated from the leaves and twigs of GARCINIA HANBURYI. Compounds 1- 3 were also isolated from the resin of this plant. The structure of 2 was confirmed by single-crystal X-ray diffraction analysis. All of the lupanes ( 1- 4) displayed anti-HIV-1 activities in the anti-HIV-1 reverse transcriptase (IC (50) values 16.3-116.9 microg/mL) and syncytium assays (EC (50) 5.6-73.6 microg/mL, SI 1.7-3.3). Moreover compounds 1- 4 exhibited anti-inflammatory activity in an ethyl phenylpropiolate (EPP)-induced ear edema model.

Pyranonaphthoquinone and anthraquinone derivatives from Ventilago harmandiana and their potent anti-inflammatory activity.

The chemical study on the heartwoods extract of Ventilago harmandiana (Rhamnaceae) resulted in the isolation of ten previously undescribed pyranonaphthoquinones (ventilanones A-J), an undescribed anthraquinone (ventilanone K), together with eight known anthraquinone derivatives. Their structures were elucidated by extensive analysis of their spectroscopic data. The absolute configuration of ventilanone A was established from single crystal X-ray crystallographic analysis of its p-bromobenzenesulfonate ester derivative using Cu Kα radiation. The absolute configurations of the other related compounds were identified by comparison of their ECD data with those of ventilanone A and related known compounds. Cytotoxic and anti-inflammatory activities of some of the isolated compounds were evaluated. Ventilanone A and ventilanone C exhibited moderate cytotoxicity against P-388 cell line. Ventilanone D exhibited significant anti-inflammatory activity while ventilanone A and ventilanone C showed moderate activity.

Fluoride-catalyzed addition of PhSCF2SiMe3 to N-substituted cyclic imides followed by radical cyclization: general synthetic strategy of gem-difluoromethylenated 1-azabicyclic compounds.

PhSCF(2)SiMe(3) (1) was found, for the first time, to undergo fluoride-catalyzed nucleophilic difluoro(phenylsulfanyl)methylation reaction to cyclic imides 2, affording the corresponding adducts 3 in moderate to good yields. Reductive cleavage of the phenylsulfanyl group of N-alkylated adducts 3 with Bu(3)SnH/AIBN yielded gem-difluoromethylated products 4. Under the same reduction conditions, N-alkenylated and N-alkynylated adducts 3 afforded the corresponding gem-difluoromethylenated 1-azabicyclic compounds 5 and 6 with trans stereoselectivity. These compounds were employed as precursors for preparing substituted gem-difluoromethylenated pyrrolizidinones and indolizidinones 7 and 8 by treatment with Et(3)SiH/BF(3) x OEt(2), and compounds 9 and 10 by nucleophilic displacement of the hydroxyl group, using organosilanes in the presence of BF(3) x OEt(2). The synthesis of highly substituted gem-difluoromethylenated pyrrolizidines 13 and 14 was also demonstrated.