The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform

Yusrida Darwis - One of the best experts on this subject based on the ideXlab platform.

  • Preparation, characterization, and in vivo evaluation of insulin-loaded PLA–PEG microspheres for controlled parenteral drug delivery
    Drug development and industrial pharmacy, 2009
    Co-Authors: Ravi Sheshala, Kok Khiang Peh, Yusrida Darwis
    Abstract:

    Aim: The aim of this study was to prepare insulin-loaded poly(lactic acid)–polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model. Methods: The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin® 30/70 as a reference product in streptozotocin-induced diabetic rats. Results: The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 ×μm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was chara...

  • preparation characterization and in vivo evaluation of insulin loaded pla peg microspheres for controlled parenteral drug delivery
    Drug Development and Industrial Pharmacy, 2009
    Co-Authors: Ravi Sheshala, Kok Khiang Peh, Yusrida Darwis
    Abstract:

    Aim: The aim of this study was to prepare insulin-loaded poly(lactic acid)–polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model. Methods: The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin® 30/70 as a reference product in streptozotocin-induced diabetic rats. Results: The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 ×μm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was chara...

Robert Verpoorte - One of the best experts on this subject based on the ideXlab platform.

  • Conversion of deoxyHumulone into the hop α-acid Humulone
    Phytochemistry, 1997
    Co-Authors: Suenying Fung, Karin W M Zuurbier, Norma Paniego, Johannes J. C. Scheffer, Robert Verpoorte
    Abstract:

    In the final step of the biosynthesis of hop bitter acids an oxidation leads to the formation of α-acids. A method was set up to analyse the bitter acids in the presence of proteins, since proteins from a crude hop extract were found to interact with the phenolic bitter acids and interfere with the extraction and assay of these acids. After examination of the interaction of bovine serum albumin with hop bitter acids, concentration of the samples by lyophilization and subsequent analysis by HPLC were used to study the conversion of deoxyHumulone into Humulone. Two types of oxidation were found to take place in vitro: a chemical reaction and a reaction catalysed by an unknown factor from hop protein extracts. The results of this study indicate that this factor, isolated from the glandular hairs of hop cones, is an enzyme that is involved in the biosynthesis of α-acids.

  • formation of aromatic intermediates in the biosynthesis of bitter acids in humulus lupulus
    Phytochemistry, 1995
    Co-Authors: Karin W M Zuurbier, Suenying Fung, Johannes J. C. Scheffer, Robert Verpoorte
    Abstract:

    Abstract A new hypothesis concerning the formation of aromatic intermediates in the biosynthesis of hop bitter acids was tested. Two phloroglucinol derivatives, 2-(3-methylbutanoyl)-1,3,5-benzenetriol (phlorisovalerophenone = PIVP) and 2-(2-methylpropanoyl)-1,3,5-benzenetriol (phlorisobutyrophenone = PIBP), were detected in hop extracts. The formation of these compounds was shown to occur in vitro in hop protein extracts using the precursors malonyl-CoA plus isovaleryl-CoA or isobutyryl-CoA, respectively. We conclude that PIVP and PIBP are probably the first aromatic intermediates formed in the biosynthesis of Humulone/lupulone and coHumulone/colupulone, respectively. We suggest that the reactions are catalysed by a chalcone synthase-like enzyme. The enzyme chalcone synthase and its activity were found to be present in hop protein extracts. The formation of naringenin, PIVP and PIBP in various hop protein extracts obtained during the development from flower bud to ripe cone was compared.

  • Preparative separation and isolation of three α bitter acids from hop, Humulus lupulus L., by centrifugal partition chromatography
    Journal of Chromatography A, 1994
    Co-Authors: A. Hermans-lokkerbol, Robert Verpoorte
    Abstract:

    Centrifugal partition chromatography was used for the preparative separation of bitter acids from a crude supercritical carbon dioxide extract of hop cones. The main α-acids, Humulone, coHumulone and adHumulone were obtained pure in one chromatographic run with the system toluene−0.1 M triethanolamine · HCl pH 8.4 in water. The two-phase system was optimized for pH and the effect of ethylene glycol on the separation was investigated.

Ravi Sheshala - One of the best experts on this subject based on the ideXlab platform.

  • Preparation, characterization, and in vivo evaluation of insulin-loaded PLA–PEG microspheres for controlled parenteral drug delivery
    Drug development and industrial pharmacy, 2009
    Co-Authors: Ravi Sheshala, Kok Khiang Peh, Yusrida Darwis
    Abstract:

    Aim: The aim of this study was to prepare insulin-loaded poly(lactic acid)–polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model. Methods: The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin® 30/70 as a reference product in streptozotocin-induced diabetic rats. Results: The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 ×μm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was chara...

  • preparation characterization and in vivo evaluation of insulin loaded pla peg microspheres for controlled parenteral drug delivery
    Drug Development and Industrial Pharmacy, 2009
    Co-Authors: Ravi Sheshala, Kok Khiang Peh, Yusrida Darwis
    Abstract:

    Aim: The aim of this study was to prepare insulin-loaded poly(lactic acid)–polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model. Methods: The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin® 30/70 as a reference product in streptozotocin-induced diabetic rats. Results: The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 ×μm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was chara...

R. M. Kamens - One of the best experts on this subject based on the ideXlab platform.

  • Gas and Particulate Products Distribution from the Photooxidation of α-Humulene in the Presence of NO_x, Natural Atmospheric Air and Sunlight
    Journal of Atmospheric Chemistry, 2003
    Co-Authors: M. Jaoui, R. M. Kamens
    Abstract:

    The photooxidation of α-humulene in the presence of NO_x, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m^3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for ∼ 44% of the reacted α-humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco-α-Humulone aldehyde, 7-seco-α-Humulone aldehyde, α-humulal aldehyde, α-humulene 3-oxide or α-humulene 7-oxide, α-humulaic/alic acid isomers, and 3-seco-α-14-hydroxyHumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.

  • Gas and Particulate Products Distribution from the Photooxidation of α-Humulene in the Presence of NOx, Natural Atmospheric Air and Sunlight
    Journal of Atmospheric Chemistry, 2003
    Co-Authors: M. Jaoui, R. M. Kamens
    Abstract:

    The photooxidation of α-humulene in the presence of NOx, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for ∼ 44% of the reacted α-humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco-α-Humulone aldehyde, 7-seco-α-Humulone aldehyde, α-humulal aldehyde, α-humulene 3-oxide or α-humulene 7-oxide, α-humulaic/alic acid isomers, and 3-seco-α-14-hydroxyHumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.

Hiroyasu Tobe - One of the best experts on this subject based on the ideXlab platform.

  • 70 – Biological Activities of Humulone
    Beer in Health and Disease Prevention, 2009
    Co-Authors: Hiroyasu Tobe
    Abstract:

    In the screening test for the substance to inhibit bone resorption, we found that Humulone (HU) from beer hop extracts showed a strong inhibitory activity to bone resorption. The value of IC50 (50% inhibition of bone resorption) was 5.9 nM in pit formation assay. To study the mechanism of the action of HU, we studied the biological activity of HU as a bone resorption inhibitor with reference to prostaglandin biosynthesis. We found that HU inhibited the transcription of cyclooxygenase-2 (COX-2) gene of osteoblast MC3T3-E1 with an IC50 of 30 nM. The recent reports demonstrated a close relationship between COX enzymes and angiogenesis. We showed also that HU as a COX-2 inhibitor inhibited angiogenesis in chick embryo chorioallantoic membrane (CAM). The value of ED50 was 1.5 μg/CAM. HU enhanced effectively the differentiation-inducing action of vitamin D to myelogenous leukemia cells in the concentration of 0.5-2.5 μM. HU also induced apoptosis (DNA fragmentation and cell death) in HL-60 cells in the concentration of 1–100 μg/ml.

  • 70 biological activities of Humulone
    Beer in Health and Disease Prevention, 2009
    Co-Authors: Hiroyasu Tobe
    Abstract:

    In the screening test for the substance to inhibit bone resorption, we found that Humulone (HU) from beer hop extracts showed a strong inhibitory activity to bone resorption. The value of IC50 (50% inhibition of bone resorption) was 5.9 nM in pit formation assay. To study the mechanism of the action of HU, we studied the biological activity of HU as a bone resorption inhibitor with reference to prostaglandin biosynthesis. We found that HU inhibited the transcription of cyclooxygenase-2 (COX-2) gene of osteoblast MC3T3-E1 with an IC50 of 30 nM. The recent reports demonstrated a close relationship between COX enzymes and angiogenesis. We showed also that HU as a COX-2 inhibitor inhibited angiogenesis in chick embryo chorioallantoic membrane (CAM). The value of ED50 was 1.5 μg/CAM. HU enhanced effectively the differentiation-inducing action of vitamin D to myelogenous leukemia cells in the concentration of 0.5-2.5 μM. HU also induced apoptosis (DNA fragmentation and cell death) in HL-60 cells in the concentration of 1–100 μg/ml.

  • suppression of cyclooxygenase 2 gene transcription by Humulon
    Advances in Experimental Medicine and Biology, 2002
    Co-Authors: Kei Yamamoto, Shozo Yamamoto, J Wang, Hiroyasu Tobe
    Abstract:

    Cyclooxygenase is the key enzyme in the biosynthetic pathway of prostaglandins (PGs) and thromboxane from arachidonic acid. There are two isozymes of cyclooxygenase; constitutive cyclooxygenase-1 and inducible cyclooxygenase-2.1’2MC3T3-E1 cell cloned from newborn mouse calvaria is an osteogenic cell line which differentiates into an osteoblast.3’4Our extensive studies demonstrated the production of PGE2as a major arachidonate metabolite in this cell linesand the induction of cyclooxygenase by various bioregulators including tumor necrosis factor a (TNFa).5-9Later the induced enzyme in MC3T3-E1 cells was identified as cyclooxygenase-2.8-10Previously Humulon ((R)-3,5,6-trihydroxy-4,6-bis(3-methyl-2-butenyl)-2-(3-methyl-1oxobutyl)-2,4-cyclohexadien-1-one) (Fig. IA) isolated from hop (Humulus lupulus L.) extract was found as an inhibitor of bone resorption with an IC50of 5.9 nM.“ We noted this activity of Humulon, and were interested in a possible inhibitory or suppressive effect of Humulon on cyclooxygenase-2 leading to a decreased production of PGE2which is well known as a bone resorption factor.12

  • Inhibition of angiogenesis by Humulone, a bitter acid from beer hop.
    Biochemical and biophysical research communications, 2001
    Co-Authors: Mariko Shimamura, Hiroyasu Tobe, Tadahiko Hazato, Hiromi Ashino, Yukio Yamamoto, Eri Iwasaki, Kei Yamamoto, Shozo Yamamoto
    Abstract:

    On the basis of our previous finding that Humulone, a bitter acid from beer hop extract, was a potent inhibitor of bone resorption and inhibited the catalytic activity of cyclooxygenase-2 (COX-2) and more potently the transcription of the COX-2 gene, we examined the effect of Humulone on angiogenesis, using chick embryo chorioallantoic membranes (CAMs) and vascular endothelial and tumor cells. Humulone significantly prevented in vivo angiogenesis in CAM in a dose-dependent manner with an ED50 of 1.5 μg/CAM. Humulone also inhibited in vitro tube formation of vascular endothelial cells. Moreover, it suppressed the proliferation of endothelial cells and the production of vascular endothelial growth factor (VEGF), an angiogenic growth factor, in endothelial and tumor cells. Thus, Humulone is a potent angiogenic inhibitor, and may be a novel powerful tool for the therapy of various angiogenic diseases involving solid tumor growth and metastasis.

  • Induction of differentiation of myelogenous leukemia cells by Humulone, a bitter in the hop
    Leukemia research, 1998
    Co-Authors: Yoshio Honma, Hiroyasu Tobe, Makoto Makishima, Akihiro Yokoyama, Junko Okabe-kado
    Abstract:

    The active form of vitamin D, 1alpha,25-dihydroxyvitamin D3 (VD3), inhibits proliferation and induces differentiation of myelomonocytic leukemia cells, but its clinical use is limited by the adverse effect of hypercalcemia. VD3 mobilizes calcium stores from bone by inducing the dissolution of bone mineral and matrix. We have recently found that Humulone, a bitter in the hop extract for beer brewing, effectively inhibits bone resorption. In this study we examined the effect of Humulone on the differentiation of human myelogenous leukemia cells. Humulone alone inhibited the growth of monoblastic leukemia U937 cells while only slightly increasing differentiation markers such as nitroblue tetrazolium (NBT)-reducing and lysozyme activities. Humulone effectively enhanced the differentiation-inducing action of VD3. Other myelomonocytic leukemia cells were induced to differentiate by VD3 and this was also enhanced by Humulone. Since Humulone is a less-toxic inhibitor of bone resorption, the combination of Humulone and VD3 may be useful in differentiation therapy of myelomonocytic leukemia.