The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Julesroger Kuiate - One of the best experts on this subject based on the ideXlab platform.
-
antibacterial and antioxidant properties of crude extract fractions and compounds from the stem bark of polyscias fulva hiern araliaceae
BMC Complementary and Alternative Medicine, 2017Co-Authors: Guy Sedar Singor Njateng, Donatien Gatsing, Raymond Simplice Mouokeu, Xiaodong Luo, Yaping Liu, Hongxia Zang, Julesroger KuiateAbstract:In our previous work, the dichloromethane-methanol (1:1 v/v) extract, fractions and isolated compounds from Polyscias fulva stem bark showed interesting antifungal activity. As a continuity of that work, this study aimed to bring out complementary informations about the antimicrobial properties of P. fulva stem bark that may be useful in the standardization of phytomedicine from this plant. The antibacterial activities of the crude extract, fractions (n-hexane, ethyl acetate, n-butanol and residual) and isolated compounds from Polyscias fulva stem bark were assayed by broth microdilution techniques. Their antioxidant activity were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), pyrogallol (superoxide anion) and β-carotene - linoleic acid assays. The crude extract presented antibacterial activities against S. typhi (ATCC 6539), E. aerogenes (ATCC 13045), P. aeruginosa (PA01) and E. coli (ATCC 10536) with MIC values of 2000 to 8000 μg/ml. The fractionation led the ethyle acetate and n-butanol fractions relatively more active (MIC = 500 to 1000 μg/ml) as compared to the crude extract. β-sitosterol and 3-O-α-L- arabinopyranosyl-hederagenin were the most active compounds on the tested bacteria with MIC values ranging from 6.25 to 100 μg/ml. The most sensitive was P. aeruginosa (PA01) on which all the tested compounds were active with MICs ranging from 6.25 to 400 μg/ml. Among all the tested substances, the crude extract (RSa50 = 84.86 μg/ml) and the methyl atrarate (RSa50 = 14.77 μg/ml), showed the highest scavenging activities against DPPH free radicals and those arising from the oxidation of the linoleic acid respectively. From this study, the results obtained reveal that the stem bark of P. fulva possesses antibacterial and antioxidant activities. It may then be useful in the development of an antimicrobial phytomedicine with a large spectrum of actvity endowed with antioxidant properties which can be standardised based on the isolated compounds.
-
antifungal properties of a new terpernoid saponin and other compounds from the stem bark of polyscias fulva hiern araliaceae
BMC Complementary and Alternative Medicine, 2015Co-Authors: Guy Sedar Singor Njateng, Donatien Gatsing, Arno Rusel Nanfack Donfack, Michel Feussi Talla, Hippolyte K Wabo, Pierre Tane, Raymond Simplice Mouokeu, Xiaodong Luo, Julesroger KuiateAbstract:In our previous studies, it was evident that the dichloromethane-methanol (1:1 v/v) stem barks extract of Polyscias fulva and fractions (ethyl acetate, n-butanol and residue) demonstrated interesting antidermatophytic activities. So, as a continuity of that, this work aimed at identifying active principles with antifungal properties from P. fulva that could be used as markers for possible standardization of this plant as phytomedicine. The ethyl acetate, n-butanol and residual fractions of the dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva were further fractionated by column chromatography and the structures of isolated compounds elucidated based on their spectroscopic data in comparison with existing literature information. Antifungal activity was assayed by broth microdilution techniques on yeasts and dermatophytes spores. The fractionation of the crude dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva led to the isolation of 10 known compounds (1 to 10) and one new saponin (11: 3-O-[α-L-rhamnopyranosyl (1–2)-α-L-arabinopyranosyl]-28-O-[α-L-4-O-acetyl-rhamnopyranosyl (1–4)-β-D-glucopyranosyl-(1–6)-β-D-glucopyranosyl]-hederagenin). Among these compounds, 3-O-α-L- arabinopyranosyl-hederagenin and 3-O-[α-L-rhamnopyranosyl (1–2)-α-L-arabinopyranosyl]-hederagenin were the most active on the tested fungi with MIC values ranging from 0.78 to 100 μg/ml against both yeasts and dermatophytes. The results of this work constitute a step forward in the possible development of an antidermatophytic phytomedicine from Polyscias fulva stem bark, the isolated compounds being possible markers for the standardisation.
Guy Sedar Singor Njateng - One of the best experts on this subject based on the ideXlab platform.
-
antibacterial and antioxidant properties of crude extract fractions and compounds from the stem bark of polyscias fulva hiern araliaceae
BMC Complementary and Alternative Medicine, 2017Co-Authors: Guy Sedar Singor Njateng, Donatien Gatsing, Raymond Simplice Mouokeu, Xiaodong Luo, Yaping Liu, Hongxia Zang, Julesroger KuiateAbstract:In our previous work, the dichloromethane-methanol (1:1 v/v) extract, fractions and isolated compounds from Polyscias fulva stem bark showed interesting antifungal activity. As a continuity of that work, this study aimed to bring out complementary informations about the antimicrobial properties of P. fulva stem bark that may be useful in the standardization of phytomedicine from this plant. The antibacterial activities of the crude extract, fractions (n-hexane, ethyl acetate, n-butanol and residual) and isolated compounds from Polyscias fulva stem bark were assayed by broth microdilution techniques. Their antioxidant activity were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), pyrogallol (superoxide anion) and β-carotene - linoleic acid assays. The crude extract presented antibacterial activities against S. typhi (ATCC 6539), E. aerogenes (ATCC 13045), P. aeruginosa (PA01) and E. coli (ATCC 10536) with MIC values of 2000 to 8000 μg/ml. The fractionation led the ethyle acetate and n-butanol fractions relatively more active (MIC = 500 to 1000 μg/ml) as compared to the crude extract. β-sitosterol and 3-O-α-L- arabinopyranosyl-hederagenin were the most active compounds on the tested bacteria with MIC values ranging from 6.25 to 100 μg/ml. The most sensitive was P. aeruginosa (PA01) on which all the tested compounds were active with MICs ranging from 6.25 to 400 μg/ml. Among all the tested substances, the crude extract (RSa50 = 84.86 μg/ml) and the methyl atrarate (RSa50 = 14.77 μg/ml), showed the highest scavenging activities against DPPH free radicals and those arising from the oxidation of the linoleic acid respectively. From this study, the results obtained reveal that the stem bark of P. fulva possesses antibacterial and antioxidant activities. It may then be useful in the development of an antimicrobial phytomedicine with a large spectrum of actvity endowed with antioxidant properties which can be standardised based on the isolated compounds.
-
antifungal properties of a new terpernoid saponin and other compounds from the stem bark of polyscias fulva hiern araliaceae
BMC Complementary and Alternative Medicine, 2015Co-Authors: Guy Sedar Singor Njateng, Donatien Gatsing, Arno Rusel Nanfack Donfack, Michel Feussi Talla, Hippolyte K Wabo, Pierre Tane, Raymond Simplice Mouokeu, Xiaodong Luo, Julesroger KuiateAbstract:In our previous studies, it was evident that the dichloromethane-methanol (1:1 v/v) stem barks extract of Polyscias fulva and fractions (ethyl acetate, n-butanol and residue) demonstrated interesting antidermatophytic activities. So, as a continuity of that, this work aimed at identifying active principles with antifungal properties from P. fulva that could be used as markers for possible standardization of this plant as phytomedicine. The ethyl acetate, n-butanol and residual fractions of the dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva were further fractionated by column chromatography and the structures of isolated compounds elucidated based on their spectroscopic data in comparison with existing literature information. Antifungal activity was assayed by broth microdilution techniques on yeasts and dermatophytes spores. The fractionation of the crude dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva led to the isolation of 10 known compounds (1 to 10) and one new saponin (11: 3-O-[α-L-rhamnopyranosyl (1–2)-α-L-arabinopyranosyl]-28-O-[α-L-4-O-acetyl-rhamnopyranosyl (1–4)-β-D-glucopyranosyl-(1–6)-β-D-glucopyranosyl]-hederagenin). Among these compounds, 3-O-α-L- arabinopyranosyl-hederagenin and 3-O-[α-L-rhamnopyranosyl (1–2)-α-L-arabinopyranosyl]-hederagenin were the most active on the tested fungi with MIC values ranging from 0.78 to 100 μg/ml against both yeasts and dermatophytes. The results of this work constitute a step forward in the possible development of an antidermatophytic phytomedicine from Polyscias fulva stem bark, the isolated compounds being possible markers for the standardisation.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
-
bioconjugatable pegylated hydroporphyrins for photochemistry and Photomedicine narrow band red emitting chlorins
New Journal of Chemistry, 2016Co-Authors: Mengran Liu, Chihyuan Chen, Amit Kumar Mandal, Vanampally Chandrashaker, Rosemary B Evansstorms, Bruce J Pitner, David F Bocian, Dewey Holten, Jonathan S LindseyAbstract:Chromophores that absorb and emit in the red spectral region (600–700 nm), are water soluble, and bear a bioconjugatable tether are relatively rare yet would fulfill many applications in photochemistry and Photomedicine. Here, three molecular designs have been developed wherein stable synthetic chlorins – analogues of chlorophylls – have been tailored with PEG groups for use in aqueous solution. The designs differ with regard to order of the installation (pre/post-formation of the chlorin macrocycle) and position of the PEG groups. Six PEGylated synthetic chlorins (three free bases, three zinc chelates) have been prepared, of which four are equipped with a bioconjugatable (carboxylic acid) tether. The most effective design for aqueous solubilization entails facial encumbrance where PEG groups project above and below the plane of the hydrophobic disk-like chlorin macrocycle. The chlorins possess strong absorption at ∼400 nm (B band) and in the red region (Qy band); regardless of wavelength of excitation, emission occurs in the red region. Excitation in the ∼400 nm region thus provides an effective Stokes shift of >200 nm. The four bioconjugatable water-soluble chlorins exhibit Qy absorption/emission in water at 613/614, 636/638, 698/700 and 706/710 nm. The spectral properties are essentially unchanged in DMF and water for the facially encumbered chlorins, which also exhibit narrow Qy absorption and emission bands (full-width-at-half maximum of each <25 nm). The water-solubility was assessed by absorption spectroscopy over the concentration range ∼0.4 μM–0.4 mM. One chlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The conjugate displayed a sharp signal when excited by a violet laser (405 nm) with emission in the 620–660 nm range. Taken together, the designs described herein augur well for development of a set of spectrally distinct chlorins with relatively sharp bands in the red region.
-
bioconjugatable pegylated hydroporphyrins for photochemistry and Photomedicine narrow band near infrared emitting bacteriochlorins
New Journal of Chemistry, 2016Co-Authors: Nuonuo Zhang, Mengran Liu, Amit Kumar Mandal, Rosemary B Evansstorms, Bruce J Pitner, David F Bocian, Dewey Holten, Jianbing Jiang, Masahiko Taniguchi, Jonathan S LindseyAbstract:Synthetic bacteriochlorins absorb in the near-infrared (NIR) region and are versatile analogues of natural bacteriochlorophylls. The utilization of these chromophores in energy sciences and Photomedicine requires the ability to tailor their physicochemical properties, including the incorporation of units to impart water solubility. Herein, we report the synthesis, from two common bacteriochlorin building blocks, of five wavelength-tunable, bioconjugatable and water-soluble bacteriochlorins along with two non-bioconjugatable benchmarks. Each bacteriochlorin bears short polyethylene glycol (PEG) units as the water-solubilizing motif. The PEG groups are located at the 3,5-positions of aryl groups at the pyrrolic β-positions to suppress aggregation in aqueous media. A handle containing a single carboxylic acid is incorporated to allow bioconjugation. The seven water-soluble bacteriochlorins in water display Qy absorption into the NIR range (679-819 nm), sharp emission (21-36 nm full-width-at-half-maximum) and modest fluorescence quantum yield (0.017-0.13). Each bacteriochlorin is neutral (non-ionic) yet soluble in organic (e.g., CH2Cl2, DMF) and aqueous solutions. Water solubility was assessed using absorption spectroscopy by changing the concentration ∼1000-fold (190-690 µM to 0.19-0.69 µM) with a reciprocal change in pathlength (0.1-10 cm). All bacteriochlorins showed excellent solubility in water, except for a bacteriochlorin-imide that gave slight aggregation at higher concentrations. One bacteriochlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The antibody conjugate of B2-NHS displayed a sharp signal upon ultraviolet laser excitation (355 nm) with NIR emission measured with a 730/45 nm bandpass filter. Overall, the study gives access to a set of water-soluble bacteriochlorins with desirable photophysical properties for use in multiple fields.
Norbert Lange - One of the best experts on this subject based on the ideXlab platform.
-
it is all about proteases from drug delivery to in vivo imaging and Photomedicine
Current Medicinal Chemistry, 2011Co-Authors: Doris Gabriel, Robert Gurny, Mariafernanda Zuluaga, H Van Den Bergh, Norbert LangeAbstract:Clinical studies provide overwhelming evidence for the importance of proteolytic imbalance and the upregulation of diverse protease classes in diseases such as cancer and arthritis. While the complex nature of proteolytic networks has hampered the development of protease inhibitors for these indications, aberrant enzyme activity could be successfully exploited for the development of proteasesensitive drug delivery systems and fluorescent in vivo imaging agents. More recently, these concepts have also been translated into photomedical applications to develop dual modality prodrugs for the simultaneous treatment and imaging of disease. After an introductory overview of proteases and their role in cancer, we present and discuss different strategies to exploit upregulated protease activity for the development of drug delivery systems, fluorescent in vivo reporter probes, and photosensitizer-prodrugs with respect to their potential and limitations. The main approaches used for targeting proteases in all three areas can be roughly divided into peptide-based and macromolecular strategies. Both involve the use of a short, peptide-based protease substrate, which is either directly tagged to the therapeutic agent or dye/quencher pair, or alternatively, serves as a linker between the polymeric carrier and a functional unit. In the latter case, the pharmacokinetic properties of peptide-based protease-sensitive prodrugs and imaging probes can be further ameliorated by the passive targeting capacity of macromolecular drug delivery systems for neoplastic and inflammatory lesions.
-
5 aminolevulinic acid derivatives in Photomedicine characteristics application and perspectives
Photochemistry and Photobiology, 2006Co-Authors: Nicolas Fotinos, Marino A Campo, Florence Popowycz, Robert Gurny, Norbert LangeAbstract:The introduction of lipophilic derivatives of the naturally occurring heme precursor 5-aminolevulinic acid (5-ALA) into Photomedicine has led to a true revival of this research area. 5-ALA-mediated photodynamic therapy (PDT) and fluorescence photodetection (FD) of neoplastic disease is probably one of the most selective cancer treatments currently known in oncology. To date, this method has been assessed experimentally for the treatment of various medical indications. However, the limited local bioavailability of 5-ALA has widely prevented its use in daily clinical practice. Although researchers were already aware of this drawback early during the development of 5-ALA-mediated PDT, only recently have well-established concepts in pharmaceutical science been adapted to investigate ways to overcome this drawback. Recently, two derivatives of 5-ALA, methylaminolevulinate (MAL) and hexylaminolevulinate (HAL), gained marketing authorization from the regulatory offices in Europe and Australia. MAL is marketed under the trade name Metvix for the treatment of actinic keratosis and difficult-to-treat basal cell carcinoma. HAL has recently been launched under the trade name Hexvix to improve the detection of superficial bladder cancer in Europe. This review will first present the fundamental concepts underlying the use of 5-ALA derivatives in PDT and FD from a chemical, biochemical and pharmaceutical point of view. Experimental evidences from preclinical data on the improvements and limits observed with 5-ALA derivatives will then be introduced. The state-of-the-art from clinical studies with 5-ALA esters will be discussed, with special emphasis placed on the process that led to the development of MAL in dermatology and to HAL in urology. Finally, we will discuss promising medical fields in which use of 5-ALA derivatives might potentially lead to further use of this methodology in Photomedicine.
Timothy Thatt Yang Tan - One of the best experts on this subject based on the ideXlab platform.
-
neodymium sensitized nanoconstructs for near infrared enabled Photomedicine
Small, 2020Co-Authors: Wen Kiat Chan, Timothy Thatt Yang TanAbstract:Neodymium (Nd3+ )-sensitized nanoconstructs have gained increasing attention in recent decades due to their unique properties, especially optical properties. The design of various Nd3+ -sensitized nanosystems is expected to contribute to medical and health applications, due to their advantageous properties such as high penetration depth, excellent photostability, non-photobleaching, low cytotoxicity, etc. However, the low conversion efficiency and potential long-term toxicity of Nd3+ -sensitized nanoconstructs are huge obstacles to their clinical translations. This review article summarizes three energy transfer pathways of all kinds of Nd3+ -sensitized nanoconstructs focusing on the properties of Nd3+ ions and discusses their recent potential applications as near-infrared (NIR) enabled Photomedicine. This review article will contribute to the design and fabrication of novel Nd3+ -sensitized nanoconstructs for NIR-enabled Photomedicine, aiming for potentially safer and more efficient designs to get closer to clinical usage.