Facile synthesis of AIEgens with wide color tunability for cellular imaging and therapy.

Luminogens with aggregation-induced emission (AIE) characteristics are nowadays undergoing explosive development in the fields of imaging, process visualization, diagnosis and therapy. However, exploration of an AIE luminogen (AIEgen) system allowing for extremely wide color tunability remains challenging. In this contribution, the facile synthesis of triphenylamine (TPA)-thiophene building block-based AIEgens having tunable maximum emission wavelengths covering violet, blue, green, yellow, orange, red, deep red and NIR regions is reported. The obtained AIEgens can be utilized as extraordinary fluorescent probes for lipid droplet (LD)-specific cell imaging and cell fusion assessment, showing excellent image contrast to the cell background and high photostability, as well as satisfactory visualization outcomes. Interestingly, quantitative evaluation of the phototherapy effect demonstrates that one of these presented AIEgens, namely TTNIR, performs well as a photosensitizer for photodynamic ablation of cancer cells upon white light irradiation. This study thus provides useful insights into rational design of fluorescence systems for widely tuning emission colors with high brightness, and remarkably extends the applications of AIEgens.

An Organocatalytic Asymmetric Synthesis of Chiral ß,ß-Diaryl-α-amino Acids via Addition of Azlactones to In Situ Generated para-Quinone Methides.

An organocatalytic intermolecular C-C bond formation process leading to the efficient synthesis of chiral ß,ß-diaryl-α-amino acid derivatives is described. In the presence of a suitable chiral phosphoric acid catalyst, a range of para-hydroxybenzyl alcohols serve as efficient precursors to para-quinone methides and then react with azlactones in 1,6-conjugate addition reactions. The asymmetric control has been carefully optimized together with diastereocontrol enabled by identification of the reversible feature of the C-C bond formation and subsequent inhibition by protection of the free hydroxy group in one pot. Compared with previous approaches, including those with pre-synthesized para-quinone methides, this protocol provides an alternative and complementary step- and pot-economical approach for the synthesis of chiral ß,ß-diaryl-α-amino acid derivatives.

Identification of New Cocrystal Systems with Stoichiometric Diversity of Salicylic Acid Using Thermal Methods.

PURPOSE: The purpose of this work was to develop thermal methods to identify cocrystal systems with stoichiometric diversity. METHODS: Differential scanning calorimetry (DSC) and hot stage microscopy (HSM) have been applied to study the stoichiometric diversity phenomenon on cocrystal systems of the model compound salicylic acid (SA) with different coformers (CCFs). The DSC method was particularly useful in the identification of cocrystal re-crystallization, especially to improve the temperature resolution using a slower heating rate. HSM was implemented as a complementary protocol to confirm the DSC results. The crystal structures were elucidated by single-crystal X-ray diffraction (SXRD). RESULTS: Two new cocrystal systems consisting of salicylic acid-benzamide (SA-BZD, 1:1, 1:2) and salicylic acid-isonicotinamide (SA-ISN, 1:1, 2:1) have been identified in the present work. The chemical structures of the newly discovered cocrystals SA-BZD (1:2) and SA-ISN (2:1) have been elucidated using X-ray single crystal and powder diffraction methods. CONCLUSIONS: The developed thermal methods could rapidly identify cocrystal systems with stoichiometric diversity, with the potential to discover new pharmaceutical cocrystals in the future.

Facile oxidation of leucomethylene blue and dihydroflavins by artemisinins: relationship with flavoenzyme function and antimalarial mechanism of action.

The antimalarial drug methylene blue (MB) affects the redox behaviour of parasite flavin-dependent disulfide reductases such as glutathione reductase (GR) that control oxidative stress in the malaria parasite. The reduced flavin adenine dinucleotide cofactor FADH(2) initiates reduction to leucomethylene blue (LMB), which is oxidised by oxygen to generate reactive oxygen species (ROS) and MB. MB then acts as a subversive substrate for NADPH normally required to regenerate FADH(2) for enzyme function. The synergism between MB and the peroxidic antimalarial artemisinin derivative artesunate suggests that artemisinins have a complementary mode of action. We find that artemisinins are transformed by LMB generated from MB and ascorbic acid (AA) or N-benzyldihydronicotinamide (BNAH) in situ in aqueous buffer at physiological pH into single electron transfer (SET) rearrangement products or two-electron reduction products, the latter of which dominates with BNAH. Neither AA nor BNAH alone affects the artemisinins. The AA-MB SET reactions are enhanced under aerobic conditions, and the major products obtained here are structurally closely related to one such product already reported to form in an intracellular medium. A ketyl arising via SET with the artemisinin is invoked to explain their formation. Dihydroflavins generated from riboflavin (RF) and FAD by pretreatment with sodium dithionite are rapidly oxidised by artemisinin to the parent flavins. When catalytic amounts of RF, FAD, and other flavins are reduced in situ by excess BNAH or NAD(P)H in the presence of the artemisinins in the aqueous buffer, they are rapidly oxidised to the parent flavins with concomitant formation of two-electron reduction products from the artemisinins; regeneration of the reduced flavin by excess reductant maintains a catalytic cycle until the artemisinin is consumed. In preliminary experiments, we show that NADPH consumption in yeast GR with redox behaviour similar to that of parasite GR is enhanced by artemisinins, especially under aerobic conditions. Recombinant human GR is not affected. Artemisinins thus may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, both by oxidising FADH(2) in parasite GR or other parasite flavoenzymes, and by initiating autoxidation of the dihydroflavin by oxygen with generation of ROS. Reduction of the artemisinin is proposed to occur via hydride transfer from LMB or the dihydroflavin to O1 of the peroxide. This hitherto unrecorded reactivity profile conforms with known structure-activity relationships of artemisinins, is consistent with their known ability to generate ROS in vivo, and explains the synergism between artemisinins and redox-active antimalarial drugs such as MB and doxorubicin. As the artemisinins appear to be relatively inert towards human GR, a putative model that accounts for the selective potency of artemisinins towards the malaria parasite also becomes apparent. Decisively, ferrous iron or carbon-centered free radicals cannot be involved, and the reactivity described herein reconciles disparate observations that are incompatible with the ferrous iron-carbon radical hypothesis for antimalarial mechanism of action. Finally, the urgent enquiry into the emerging resistance of the malaria parasite to artemisinins may now in one part address the possibilities either of structural changes taking place in parasite flavoenzymes that render the flavin cofactor less accessible to artemisinins or of an enhancement in the ability to use intra-erythrocytic human disulfide reductases required for maintenance of parasite redox balance.

Selective and efficient cycloisomerization of alkynols catalyzed by a new ruthenium complex with a tetradentate nitrogen-phosphorus mixed ligand.

The new ruthenium complex [Ru(N(3)P)(OAc)][BPh(4)] (4), in which N(3)P is the N,P mixed tetradentate ligand N,N-bis[(pyridin-2-yl)methyl]-[2-(diphenylphosphino)phenyl]methanamine was synthesized. The complex was found to be catalytically active for the endo cycloisomerization of alkynols. The catalytic reactions can be used to synthesize five-, six-, and seven-membered endo-cyclic enol ethers in good to excellent yields. A catalytic cycle involving a vinylidene intermediate was proposed for the catalytic reactions. Treatment of complex 4 with PhC[triple bond]CH and H(2)O gave the alkyl complex [Ru(CH(2)Ph)(CO)(N(3)P)][BPh(4)] (30), which supports the assumption that the catalytic reactions involve addition of a hydroxyl group to the C=C bond of vinylidene ligands.

Sesquiterpenoids from Homalomena occulta affect osteoblast proliferation, differentiation and mineralization in vitro.

Chemical investigation of rhizomes of Homalomena occulta (Lours) resulted in isolation and identification of two sesquiterpenoids (6,7), and one daucane ester 8, together with five known sesquiterpenoids, oplodiol, oplopanone, homalomenol C, bullatantriol, and 1beta,4beta,7alpha-trihydroxyeudesmane. Their structures were elucidated using 1D and 2D NMR spectroscopic and X-ray analyses. The chloroform extract of this plant and compounds 1-7 were tested in vitro for their activities in stimulating osteoblast (OB) proliferation, differentiation and mineralization. Compounds 1-4 had a stimulative effect on significantly proliferation and differentiation of culture osteoblasts, while the chloroform extract and 1 significantly stimulated mineralization of cultured osteoblasts in vitro.

Antibacterial diterpenoids from Sagittaria pygmaea.

There were five new diterpenoids, 18-beta-D-3',4'-diacetoxyxylopyranosyl-ent-kaur-16-ene (1), 18-beta-L-3',5'-diacetoxyarabinofuranosyl-ent-kaur-16-ene (2), 18-beta-D-3',6'-diacetoxyglucopyranosyl-ent-kaur-16-ene (3), ent-isopimar-8(14),15-dien-19-oic acid (4), and 5alpha-hydroxy-ent-rosa-15-en-18-oic acid (5), isolated from the whole herb of Sagittaria pygmaea. Their structures and relative configurations were established based on spectroscopic studies, chemical methods, and X-ray crystallographic analysis. Compound 2 exhibited significant antibacterial activity against the oral pathogens, Streptococcus mutans ATCC 25 175 and Actinomyces viscosus ATCC 27 044, with MIC values against both pathogens of 15.6 microg/mL. Compound 3 was active against only A. viscosus ATCC 27 044 with an MIC value of 62.5 microg/mL. Compounds 4 and 5 were active against S. mutans ATCC 25 175 and A. viscosus ATCC 27 044, with MIC values against both pathogens of 125.0 microg/mL.

ent-rosane and labdane diterpenoids from Sagittaria sagittifolia and their antibacterial activity against three oral pathogens.

Seven new ent-rosane diterpenoids, sagittines A-G (1-7), together with one new labdane diterpene, 13-epi-manoyl oxide-19-O-alpha-l-2',5'-diacetoxyarabinofuranoside (8), were isolated from the whole plant of Sagittaria sagittifolia. The structures and relative configurations of 1-8 were characterized using spectroscopic means, chemical methods, and X-ray crystallography. Compounds 1-4 exhibited antibacterial activity against the oral pathogens Streptococcus mutans ATCC 25175 and Actinomyces naeslundiis ATCC 12104, with MIC values between 62.5 and 125 microg/mL. Compound 5 was active against only A. naeslundiis ATCC 12104, with an MIC value of 62.5 microg/mL.

Cytotoxic diterpenoids from the roots of Euphorbia ebracteolata.

Three new diterpenoids, yuexiandajisu D (1), E (2) and F were isolated from the roots of Euphorbia ebracteolata, along with eight known diterpenoids, jolkinolide B (4), jolkinolide A, ent-11alpha-hydroxyabieta-8(14),13(15)-dien-16,12alpha-olide (6), ent-(13S)-hydroxyatis-16-ene-3,14-dione, ent-3beta,(13S)-dihydroxyatis-16-en-14-one, ent-3-oxokaurane-16alpha,17-diol, ent-16alpha,17-dihydroxyatisan-3-one and ent-atisane-3beta,16alpha,17-triol. The structures of all compounds were deduced using spectroscopic methods and confirmed for 1 and 2 by single-crystal X-ray diffraction. A biogenetic pathway for the formation of 1 and 2 is proposed briefly. Cytotoxic activities were evaluated against ANA-1, B 16 and Jurkat tumor cells. Jolkinolide B (4) displayed modest activity on ANA-1, B 16 and Jurkat tumor cells with IC50 values 4.46 x 10(-2), 4.48 x 10(-2), 6.47 x 10(-2) microM, and ent-11alpha-hydroxyabieta-8(14),13(15)-dien-16,12alpha-olide (6) showed significant activity against ANA-1 and Jurkat cells with IC50 values 7.12 x 10(-3) and 1.79 x 10(-2) microM. Compound 1 was found to be slightly active against ANA-1 cells with an IC50 value 2.88 x 10(-1)microM. Structure-activity relationships of isolated compounds are also discussed.