The Discovery and Biosynthesis of Nicotinic Myxochelins from an Archangium sp. SDU34.

Myxobacteria are a prolific source of structurally diverse natural products, and one of the best-studied myxobacterial products is the siderophore myxochelin. Herein, we report two new compounds, myxochelins N (1) and O (2), that are nicotinic paralogs of myxochelin A, from the terrestrial myxobacterium Archangium sp. SDU34; 2 is functionalized with a rare 2-oxazolidinone. A precursor-feeding experiment implied that the biosynthesis of 1 or 2 was due to altered substrate specificity of the loading module of MxcE, which likely accepts nicotinic acid and benzoic acid instead of more conventional 2,3-dihydroxybenzoic acid. We also employed a phylogenomic approach to map the evolutionary relationships of the myxochelin biosynthetic gene clusters (BGCs) in all the available myxobacterial genomes, to pave the way for the future discovery of potentially hidden myxochelin derivatives. Although the biological function of 1 and 2 is unclear yet, this work underpins that even extensively studied BGCs in myxobacteria can still produce new chemistry.

A mitochondria-targeted fluorescent probe for the detection of endogenous SO2 derivatives in living cells.

A unique fluorescent probe (ZACA) for the monitoring of SO2 derivatives was developed from coumarin and benzoindoles based on FRET and ICT. ZACA exhibited an active emission signal, large Stokes shift, wide emission window distance, and high photostability. It also possessed many advantages in the ratiometric detection of HSO3-/SO32- including low detection limit and high selectivity and sensitivity. Importantly, ZACA was successfully applied in the ratiometric detection of endogenous HSO3-/SO32- in living cells with excellent cellular imaging capability (1 µM) and mitochondria-targeting ability (co-localization coefficient: 0.91).

Acetyl-11-keto-ß-boswellic acid suppresses docetaxel-resistant prostate cancer cells in vitro and in vivo by blocking Akt and Stat3 signaling, thus suppressing chemoresistant stem cell-like properties.

Acquired docetaxel-resistance of prostate cancer (PCa) remains a clinical obstacle due to the lack of effective therapies. Acetyl-11-keto-ß-boswellic acid (AKBA) is a pentacyclic triterpenic acid isolated from the fragrant gum resin of the Boswellia serrata tree, which has shown intriguing antitumor activity against human cell lines established from PCa, colon cancer, malignant glioma, and leukemia. In this study, we examined the effects of AKBA against docetaxel-resistant PCa in vitro and in vivo as well as its anticancer mechanisms. We showed that AKBA dose-dependently inhibited cell proliferation and induced cell apoptosis in docetaxel-resistant PC3/Doc cells; its IC50 value in anti-proliferation was ∼17 µM. Furthermore, AKBA dose-dependently suppressed the chemoresistant stem cell-like properties of PC3/Doc cells, evidenced by significant decrease in the ability of mammosphere formation and down-regulated expression of a number of stemness-associated genes. The activation of Akt and Stat3 signaling pathways was remarkably enhanced in PC3/Doc cells, which contributed to their chemoresistant stem-like phenotype. AKBA (10-30 µM) dose-dependently suppressed the activation of Akt and Stat3 signaling pathways in PC3/Doc cells. In contrast, overexpression of Akt and Stat3 significantly attenuated the inhibition of AKBA on PC3/Doc cell proliferation. In docetaxel-resistant PCa homograft mice, treatment with AKBA significantly suppresses the growth of homograft RM-1/Doc, equivalent to its human PC3/Doc, but did not decrease their body weight. In summary, we demonstrate that AKBA inhibits the growth inhibition of docetaxel-resistant PCa cells in vitro and in vivo via blocking Akt and Stat3 signaling, thus suppressing their cancer stem cell-like properties.

Jungermannenone A and B induce ROS- and cell cycle-dependent apoptosis in prostate cancer cells in vitro.

AIM: Jungermannenone A and B (JA, JB) are new ent-kaurane diterpenoids isolated from Chinese liverwort Jungermannia fauriana, which show anti-proliferation activities in cancer cells. In this study we investigated the mechanisms underlying the anticancer action of JA and JB in PC3 human prostate cancer cells in vitro. METHODS: A panel of 9 human cancer cell lines was tested. Cell proliferation was assessed with a real-time cell analyzer and MTT assay. Cell apoptosis, cell cycle distribution and ROS levels were measured using cytometry. Mitochondrial damage was examined by transmission electron microscopy. DNA damage was detected with comet assay. Apoptotic, DNA damage- and cell cycle-related proteins were analyzed using Western blotting. The expression of DNA repair genes was measured with qRT-PCR. RESULTS: Both JA and JB exerted potent anti-proliferative action against the 9 cancer cell lines, and PC3 cells were more sensitive with IC50 values of 1.34±0.09 and 4.93±0.20 µmol/L, respectively. JA (1.5 µmol/L) and JB (5 µmol/L) induced PC3 cell apoptosis, which was attenuated by the caspase inhibitor Z-VAD. Furthermore, both JA and JB caused mitochondrial damage and ROS accumulation in PC3 cells, whereas vitamin C blocked the ROS accumulation and attenuated the cytotoxicity of JA and JB. Moreover, both JA and JB induced DNA damage, accompanied by downregulated DNA repair proteins Ku70/Ku80 and RDA51. JA induced marked cell cycle arrest at the G0/G1 phase, which was related to c-Myc suppression, whereas JB enforced the cell cycle blockade in the G2/M phase, which associated with activation of the JNK signaling. CONCLUSION: Both JA and JB induce prostate cancer apoptosis via ROS accumulation and induction of cell cycle arrest.

Diterpenoids from the Chinese liverwort Heteroscyphus tener and their antiproliferative effects.

Four new ent-labdane diterpenoids, heteroscyphins A-D (1-4), and four known diterpenoids (5-8) were isolated from the Chinese liverwort Heteroscyphus tener (Steph.) Schiffn. The absolute configuration of compound 1 was defined by single-crystal X-ray diffraction using Cu Kα radiation. Cytotoxicity tests revealed that compounds 3 and 5 exhibited modest activity against seven cancer cell lines. Compound 5 showed inhibitory effects on prostate cancer (PCa) cell proliferation but with less inhibition on non-neoplastic prostate epithelial cells. Compound 5 markedly caused cell growth arrest at the G0/G1 phase and induced cellular apoptosis through ROS-mediated DNA damage in PCa cells.

Cembrane-type diterpenoids from the Chinese liverworts Chandonanthus hirtellus and C. birmensis.

Six new cembrane-type diterpenoids (1-6) were isolated from two species of Chandonanthus: Chandonanones A, B, and D-F (1, 2, and 4-6) were isolated from C. hirtellus, and chandonanones B, C, E, and F (2, 3, 5, and 6) from C. birmensis. Five known diterpenoids, (8E)-4α-acetoxy-12α,13α-epoxycembra-1(15),8-diene (7), isochandonanthone (8), chandonanthone (9), anadensin (10), and 2,10,14-triacetoxy-7,8,18,19-diepoxydolabell-3(E)-ene (11), were also obtained. The structures of the new metabolites were established by analyses of their spectroscopic data (1D NMR, 2D NMR, HRESIMS, and IR). The absolute configurations of compounds 1 and 2 were unequivocally confirmed using single-crystal X-ray diffraction analysis with Cu Kα radiation. Cytotoxicity tests of the isolated diterpenoids against seven cancer cell lines (DU145, PC3, A549, PC12, NCI-H292, NCI-H1299, and A172) revealed that some of the diterpenoids had weak activity.

Notolutesins A-J, dolabrane-type diterpenoids from the Chinese liverwort Notoscyphus lutescens.

Ten new dolabrane-type diterpenoids, notolutesins A-J (1-10), were isolated from the Chinese liverwort Notoscyphus lutescens, along with four known compounds. The structures of the new compounds were established on the basis of extensive spectroscopic data, and that of 1 was confirmed by single-crystal X-ray crystallography. The absolute configuration of 1 was determined by comparing its experimental and calculated electronic circular dichroism spectra. All of the isolates were evaluated for their cytotoxicity against a small panel of human cancer cell lines, and compound 1 exhibited an IC50 value of 6.2 µM against the PC3 human prostate cancer cell line.

A near-infrared fluorescent probe for simultaneous detection of pH and viscosity.

In this work, we developed a ratiometric fluorescent probe (NT) based on ICT framework in near-infrared (NIR) which could detect pH and viscosity simultaneously. Long emission wavelength in NIR could protect the probe from interference of background fluorescence and improve the accuracy of the test. Due to the presence of thiazole-salt, the probe possessed good water solubility and could respond immediately to pH in water system. The pH values measured by NT in the actual samples were not much different from that measured by the pH meter, therefore, NT could give excellent accuracy. NT realized the reversible detection of pH by protonation and deprotonation. NT was used successfully to detect the pH of actual water samples, human serum and meat, as well as the viscosity variation caused by thickeners. Additionally, NT could monitor the changes of pH and viscosity in living cells. Therefore, the novel probe exhibited potential application in the fields of the environment, human health and food safety evaluation.

NBD-based colorimetric and ratiometric fluorescent probe in NIR for bisulfite.

This work presented a FRET-ICT based fluorescent probe (named NTC) composed of coumarin-benzothiazole as the acceptor and 4-nitrobenzo[c][1,2,5] oxadiazole (NBD) as the donor for the detection of SO2 derivatives in NIR. Probe NTC possessed superior performance including selectivity, quickly response toward SO32-/HSO3- and high energy transfer efficiency (94 %). The test strips provided a simple and effective tool in detecting the presence of bisulfite. Besides, NTC was applied to test the sulfur dioxide derivatives in food samples and cells.

A ratiometric fluorescent probe based on the FRET platform for the detection of sulfur dioxide derivatives and viscosity.

BACKGROUND: Sulfur dioxide (SO2) is a common gaseous pollutant that significantly threatens environmental pollution and human health. Meanwhile, viscosity is an essential parameter of the intracellular microenvironment, manipulating many physiological roles such as nutrient transport, metabolism, signaling regulation and apoptosis. Currently, most of the fluorescent probes used for detecting SO2 derivatives and viscosity are single-emission probes or probes based on the ICT mechanism, which suffer from short emission wavelengths, small Stokes shifts or susceptibility to environmental background. Therefore, the development of powerful high-performance probes for real-time monitoring of sulfur dioxide derivatives and viscosity is of great significance for human health. RESULTS: In this research, we designed the fluorescent probe QQC to detect SO2 derivatives and viscosity based on FRET platform with quinolinium salt as donor and quinolinium-carbazole as acceptor. QQC exhibited a ratiometric fluorescence response to SO2 with a low detection limit (0.09 µM), large Stokes shift (186 nm) and high energy transfer efficiency (95 %), indicating that probe QQC had good sensitivity and specificity. In addition, QQC was sensitive to viscosity, with an 9.10-folds enhancement of orange fluorescence and an excellent linear relationship (R2 = 0.98) between the logarithm of fluorescence intensity at 592 nm and viscosity. Importantly, QQC could not only recognize SO2 derivatives in real water samples and food, but also detect viscosity changes caused by food thickeners and thereby had broad market application prospects. SIGNIFICANCE: We have developed a ratiometric fluorescent probe based on the FRET platform for detecting sulfur dioxide derivatives and viscosity. QQC could not only successfully detect SO2 derivatives in food and water samples, but also be made into test strips for detecting HSO3-/SO32- solution. In addition, the probe was also used to detect viscosity changes caused by food thickeners. Therefore, this novel probe had significant value in food and environmental detection applications.

Novel fluorescence probe for ClO- in living cells: Based on FRET mechanism.

Hypochlorous acid (HClO) as a kind of reactive oxygen species (ROS) plays a vital role in many biological processes. Organic fluorescence probes have attracted great interests for the detection of HClO, due to their relatively high selectivity and sensitivity, satisfactory spatiotemporal resolution and good biocompatibility. Constructing fluorescence probes to detect HClO with advantages of large Stokes shift, wide emission gap, near infrared emission and good water solubility is still challenging. In this work, a new ratiometric fluorescence probe (named HCY) for HClO was developed. FRET-based HCY was constructed by bonding a coumarin and a flavone fluorophore. In absence of HClO, HCY exists FRET process, however, FRET is inhibited in the presence of HClO because the conjugated double bond broke. Due to the good match of the emission spectrum of the donor and the absorption spectrum of the acceptor, the FRET system appears favorable energy transfer efficiency. HCY showed high sensitivity and rapid response time. The linearity between the ratios of fluorescence intensity and concentration of HClO was established with a low limit of detection. What's more, HCY was also applied for fluorescence images of HClO in RAW264.7 cells.

A highly sensitive ratiometric fluorescent probe for detecting HSO3-/SO32- and viscosity change based on FRET/TICT mechanism.

BACKGROUND: Sulfur dioxide (SO2) is a significant gas signaling molecule in organisms, and viscosity is a crucial parameter of the cellular microenvironment. They are both involved in regulating many physiological processes in the human body. However, abnormalities in SO2 and viscosity levels are associated with various diseases, such as cardiovascular disease, lung cancer, respiratory diseases, neurological disorders, diabetes and Alzheimer's disease. Hence, it is essential to explore novel and efficient fluorescent probes for simultaneously monitoring SO2 and viscosity in organisms. RESULTS: We selected quinolinium salt with good stability, high fluorescence intensity, good solubility and low cytotoxicity as the fluorophore and developed a highly sensitive ratiometric probe QQD to identify SO2 and viscosity changes based on Förster resonance energy transfer/twisted intramolecular charge transfer (FRET/TICT) mechanism. Excitingly, compared with other probes for SO2 detection, QQD not only identified HSO3-/SO32- with a large Stokes shift (218 nm), low detection limit (1.87 µM), good selectivity, high energy transfer efficiency (92 %) and wide recognition range (1.87-200 µM), but also identified viscosity with a 26-fold fluorescence enhancement and good linearity. Crucially, QQD was applied to detect HSO3-/SO32- and viscosity in actual water and food samples. In addition, QQD had low toxicity and good photostability for imaging HSO3-/SO32- and viscosity in cells. These results confirmed the feasibility and reliability of QQD for HSO3-/SO32- and viscosity imaging and environmental detection. SIGNIFICANCE: We reported a unique ratiometric probe QQD for detecting HSO3-/SO32- and viscosity based on the quinolinium skeleton. In addition to detecting HSO3-/SO32- and viscosity change in actual water and food samples, QQD could also monitor the variations of HSO3-/SO32- and viscosity in cells, which provided an experimental basis for further exploration of the role of SO2 derivatives and viscosity in biological systems.

A near-infrared fluorescent probe based FRET for ratiometric sensing of H2O2 and viscosity in live cells.

Hydrogen peroxide (H2O2) and viscosity play vital roles in the cellular environment as signaling molecule and microenvironment parameter, respectively, and are associated with many physiological and pathological processes in biological systems. We developed a near-infrared fluorescent probe, CQ, which performed colorimetric and ratiometric detection of H2O2 and viscosity based on the FRET mechanism, and was capable of monitoring changes in viscosity and H2O2 levels simultaneously through two different channels. Based on the specific reaction of H2O2 with borate ester, CQ exhibited a significant ratiometric response to H2O2 with a large Stokes shift of 221 nm, a detection limit of 0.87 µM, a near-infrared emission wavelength of 671 nm, a response time of 1 h, a wide detection ranges of 0.87-800 µM and a high energy transfer efficiency of 99.9 %. CQ could also recognize viscosity by the TICT mechanism, and efficiently detect viscosity changes caused by food thickeners. More importantly, CQ could successfully detect endogenous/exogenous H2O2 and viscosity in live HeLa cells, which was expected to be a practical tool for detecting H2O2 and viscosity in live cells.

Highly oxygenated ent-pimarane-type diterpenoids from the Chinese liverwort Pedinophyllum interruptum and their allelopathic activities.

Ten highly oxygenated ent-pimarane-type diterpenoids, pedinophyllols A-J (1-10), were isolated from the Chinese liverwort Pedinophyllum interruptum. Their structures were determined by comprehensive analysis of spectroscopic data together with single-crystal X-ray diffraction analysis. The absolute configurations were elucidated by comparison of experimental and theoretically calculated electronic circular dichroism spectra. Allelopathic testing showed that several new diterpenoids inhibited germination of Arabidopsis thaliana seeds.

cis-clerodane diterpenes from the liverwort Scapania ciliata.

Chemical investigation of the Chinese liverwort Scapania ciliata led to the isolation of four new cis-clerodane lactones, named ciliatolides A-D (1-4, resp.), among which compound 1 was found to be a tetranorclerodanoid. Their structures were determined by extensive analysis of spectroscopic data, and, in the case of compound 1, together with a single-crystal X-ray diffraction analysis. The absolute configurations were established by analysis of the CD spectra and by quantum-chemical CD calculations. The cytotoxicities of compounds 1-4 were preliminarily tested against the PC3 and MCF-7 cell lines.

Terpenoids from the Chinese liverwort Plagiochila pulcherrima and their cytotoxic effects.

Three new pimarane-type diterpenoids, 7ß,11α-dihydroxypimara-8(14),15-diene (1), 1ß,11α-dihydroxypimara-8(14),15-diene (2), and 11α-hydroxypimara-8(14),15-diene (3), five 2,3-secoaromadendrane-type sesquiterpenoids, including a new one, ethyoxyplagiochiline A2 (4), and three known fusicoccane-type diterpenoids were isolated from the Chinese liverwort Plagiochila pulcherrima. Their structures were established on the basis of extensive spectroscopic analysis. Compounds 6 and 7 exhibited moderate inhibitory activity on the proliferation of human cancer cell lines Hela, A172, and H460. Moreover, the cytotoxicity of compound 6 to Hela cells was related to apoptotis as confirmed by DAPI nuclear staining and flow cytometry.

Dual-response and lysosome-targeted fluorescent probe for viscosity and sulfur dioxide derivatives.

Viscosity and sulfur dioxide levels are important factors to evaluate the changes of cell micro-environment because a series of diseases usually occur when they are abnormal. At present, dual-response probes that can detect both viscosity and sulfur dioxide are rare. Therefore, we developed a novel fluorescent probe CBN for simultaneous detection of sulfur dioxide and viscosity. Besides, probe CBN could target lysosome of which normal function will be disrupted by the abnormality of viscosity. Therefore, probe CBN has the potential to be served as an effective biological tool to monitor the intracellular micro-environment.

FRET-based fluorescent probe with favorable water solubility for simultaneous detection of SO2 derivatives and viscosity.

The intracellular viscosity is an important parameter of the microenvironment and SO2 is a vital gas signal molecule. At present, some dual-response fluorescence probes for simultaneous measurements of viscosity and SO2 derivatives (HSO3-/SO32-) possessed poor water solubility. In this work, we developed a water-soluble fluorescence probe CIJ (0.0864 g/100 mL of water at 20 °C) for simultaneous measurements of viscosity and SO2 derivatives. CIJ exhibited a sensitive fluorescence enhancement to environmental viscosity from 0.97 to 28.04 cP based on a twisted intramolecular charge transfer mechanism and was applied to effective measurement of viscosity in vitro and in vivo. CIJ could also respond to SO2 derivatives with a low detection limit (44 nM) and a fast response time (5 min) based on the nucleophilic addition reaction. Furthermore, CIJ was applied to monitor SO2 derivatives in ratiometric response manner in living cells.

Steroids from Commiphora mukul display antiproliferative effect against human prostate cancer PC3 cells via induction of apoptosis.

Two new stigmastane-type steroids, stigmasta-5,22E-diene-3ß,11α-diol (1) and stigmasta-5,22E-diene-3ß,7α,11α-triol (2), together with eight known compounds, were isolated from the resinous exudates of Commiphora mukul. Their structures were established by extensive analysis of their HR-MS, 1D- and 2D-NMR (COSY, HMQC, HMBC and NOESY) spectra. The isolates were evaluated for their antiproliferative activities against four human cancer cell lines. Compound 2 demonstrated inhibitory effects with IC(50) values of 5.21, 9.04, 10.94 and 16.56 µM, respectively, against K562, MCF-7, PC3 and DU145 human cancer cell lines. Further study showed that 2 was able to enforce the PC3 cell cycle arrest in the G2/M phase, and induce the apoptosis of PC3 cells by activation of Bax, caspases 3 and 9, and by inhibition of Bcl-2. It was also found that 1 inhibited proliferation of PC3 cells via G0/G1 phase arrest of the cell cycle.

Two simple but effective turn-on benzothiazole-based fluorescent probes for detecting hydrogen sulfide in real water samples and HeLa cells.

Two simple turn-on fluorescent probes, containing a benzothiazole and the 2,4-dinitrobenzenesulfonyl group, were designed for detecting H2S. Two probes exhibited good selectivity and high sensitivity, which were applied to detect the H2S in real water samples. Probe P2 with a positive charge had better solubility than probe P1 in water; therefore, probe P2 was successfully applied to detect both the endogenous and exogenous H2S in lysosomes of living HeLa cells.