scholarly journals Selective inhibition of Rhizopus eumelanin biosynthesis by novel natural product scaffold-based designs caused significant inhibition of fungal pathogenesis

2020 ◽  
Vol 477 (13) ◽  
pp. 2489-2507
Author(s):  
Sameh S. M. Soliman ◽  
Rania Hamdy ◽  
Samia A. Elseginy ◽  
Teclegiorgis Gebremariam ◽  
Alshaimaa M. Hamoda ◽  
...  
Keyword(s):  
Natural Product ◽  
Mammalian Cells ◽  
Kojic Acid ◽  
Selective Inhibition ◽  
Positive Control ◽  
Significant Inhibition ◽  
Putative Virulence Factor ◽  
Melanin Production ◽  
Fungal Melanin ◽  
Immunocompetent Mice

Melanin is a dark color pigment biosynthesized naturally in most living organisms. Fungal melanin is a major putative virulence factor of Mucorales fungi that allows intracellular persistence by inducing phagosome maturation arrest. Recently, it has been shown that the black pigments of Rhizopus delemar is of eumelanin type, that requires the involvement of tyrosinase (a copper-dependent enzyme) in its biosynthesis. Herein, we have developed a series of compounds (UOSC-1–14) to selectively target Rhizopus melanin and explored this mechanism therapeutically. The compounds were designed based on the scaffold of the natural product, cuminaldehyde, identified from plant sources and has been shown to develop non-selective inhibition of melanin production. While all synthesized compounds showed significant inhibition of Rhizopus melanin production and limited toxicity to mammalian cells, only four compounds (UOSC-1, 2, 13, and 14) were selected as promising candidates based on their selective inhibition to fungal melanin. The activity of compound UOSC-2 was comparable to the positive control kojic acid. The selected candidates showed significant inhibition of Rhizopus melanin but not human melanin by targeting the fungal tyrosinase, and with an IC50 that are 9 times lower than the reference standard, kojic acid. Furthermore, the produced white spores were phagocytized easily and cleared faster from the lungs of infected immunocompetent mice and from the human macrophages when compared with wild-type spores. Collectively, the results suggested that the newly designed derivatives, particularly UOSC-2 can serve as promising candidate to overcome persistence mechanisms of fungal melanin production and hence make them accessible to host defenses.

Synthesis and Structure−Activity Relationship Studies of N-monosubstituted Aroylthioureas as Urease Inhibitors

2020 ◽  
Vol 16 ◽  
Author(s):  
Wei-Wei Ni ◽  
Hai-Lian Fang ◽  
Ya-Xi Ye ◽  
Wei-Yi Li ◽  
Li Liu ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Mammalian Cells ◽  
Intact Cell ◽  
Linear Regression Analysis ◽  
Positive Control ◽  
Acetohydroxamic Acid ◽  
Urease Inhibitors ◽  
Ic50 Value ◽  
Ic50 Values ◽  
Low Cytotoxicity

Background: Thiourea is a classical urease inhibitor usually as a positive control, and many N,N`-disubstituted thioureas have been determined as urease inhibitors. However, due to steric hindrance, N,N`-disubstituted thiourea motif could not bind urease as thiourea. On the contrary, N-monosubstituted thioureas with a tiny thiourea motif could theoretically bind into the active pocket as thiourea. Objective: A series of N-monosubstituted aroylthioureas were designed and synthesized for evaluation as urease inhibitors. Methods: Urease inhibition was determined by the indophenol method and IC50 values were calculated using computerized linear regression analysis of quantal log dose-probit functions. The kinetic parameters were estimated viasurface plasmon resonance (SPR) and by nonlinear regression analysis based on the mixed type inhibition model derived from Michaelis-Menten kinetics. Results: Compounds b2, b11and b19 reversibly inhibited urease with a mixed mechanism, and showed excellent potency against both cell-free urease and urease in intact cell, with IC50 values being 90-to 450-fold and 5-to 50-fold lower than the positive control acetohydroxamic acid, respectively. The most potent compound b11 showed IC50 value of 0.060 ±0.004μM against cell-free urease, which bound to urea binding site with a very low KDvalue (0.420±0.003nM) and a very long residence time (6.7 min). Compound b11was also demonstrated having very low cytotoxicity to mammalian cells. Conclusion: These results revealed that N-monosubstituted aroylthioureas clearly bind the active site of urease as expected, and represent a new class of urease inhibitors for the development of potential therapeutics against infections caused by ure-ase-containing pathogens.

Effect of selective inhibition of the p38 MAP kinase pathway on platelet aggregation

2004 ◽  
Vol 92 (12) ◽  
pp. 1387-1393 ◽  
Author(s):  
Athan Kuliopulos ◽  
Ramon Mohanlal ◽  
Lidija Covic
Keyword(s):  
Platelet Aggregation ◽  
P38 Mapk ◽  
Coronary Intervention ◽  
Selective Inhibition ◽  
P38 Map Kinase ◽  
Significant Inhibition ◽  
Mitogen Activated Protein Kinase ◽  
Thromboxane Production ◽  
Mapk Inhibitor

SummarySystemic inflammation has been shown to be a contributing factor to the instability of atherosclerotic plaques in patients with acute coronary syndromes (ACS). VX-702, a novel p38 mitogen-activated protein kinase (MAPK) inhibitor, is currently under investigation in ACS patients with unstable angina to evaluate its safety and efficacy during percutaneous coronary intervention (PCI).The role of p38 MAPK in platelet aggregation of normal individuals was examined using the selective second generation p38 MAPK inhibitor VX-702. Treatment of platelets with thrombin (activates PAR1 and PAR4 thrombin receptors), SFLLRN (PAR1), AYPGKF (PAR4), collagen (α2β1 and GPVI/FCγIIR receptors) and U46619 (TXA2) resulted in strong activation of p38 MAPK. Activation of the GPIb von Willebrand factor receptor with ristocetin did not stimulate p38 MAPK. Pre-treatment of platelets with 1 μM VX-702 completely inhibited activation of p38 MAPK by thrombin, SFLLRN, AYPGKF, U46619, and collagen. There was no effect of VX-702 on platelet aggregation induced by any of the agonists in the presence or absence of aspirin, heparin or apyrase. It has been postulated that a potential role of p38 MAPK is to activate phospholipase A2 (cPLA2) which catalyses formation of arachidonic acid leading to production of thromboxane. Interestingly, we show contrasting effects of p38 MAPK inhibition as compared to aspirin inhibition on platelet aggregation in response to collagen. Blockade of TXA2 production by aspirin results in significant inhibition of collagen activation. However, VX-702 has no effect on collagen-mediated platelet aggregation, suggesting that blocking p38 MAPK does not effect thromboxane production in human platelets. Therefore, unlike aspirin blockade of thromboxane production in platelets, p38 MAPK inhibitors such as VX-702 do not significantly affect platelet function and would not be expected to contribute to an elevated risk of bleeding side-effects in treated patients.

scholarly journals Uji Bioaktivitas Antibakteri Senyawa murni dari Jamur Endofit Sporothrix sp Terhadap Bakteri Escherichia coli dan Staphylococcus aureus

2019 ◽  
Vol 6 (1) ◽  
pp. 37
Author(s):  
Dewi Yudiana Shinta ◽  
Yusmarini Yusmarini ◽  
Herix Sonata MS ◽  
Hilwan Yuda Teruna ◽  
Saryono Saryono
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Endophytic Fungi ◽  
Positive Control ◽  
Significant Inhibition ◽  
New Drugs ◽  
Diffusion Method ◽  
Significant Difference ◽  
Pure Compounds ◽  
Escherichia Coli Bacteria

Modern medicines that are developing now come from active ingredients isolated from plants that require large amounts of plants. The development of new drugs from endophytic fungi found obstacles in the amount of pure compounds produced. Therefore further research is needed by using endophytic fungi as a new antimicrobial producer. This study aims to see the ability or activity of pure compounds produced by Sporothrix sp endophytic fungi from Dahlia tuber (Dahlia variabilis). Test the activity of pure compounds produced by Sporothrix sp. Endophytic fungi on E. coli and Staphylococcus aureus determined by disc diffusion method. With doses of 10, 30 and 50μg/disk. In Escherichia coli bacteria doses 10 and 50μg/disk gave significant inhibition of pure compounds from isolation compared to the positive control of ciprofloxacin, which was marked by a statistically significant test result (p <0.05). In contrast to Staphylococcus aureus there was no significant difference in doses of both doses of 10.30 and 50μg/disk. Determination of pure compounds was carried out by HPLC and Infra Red Spectrophotometry.

Uptake of biotin by native Xenopus laevis oocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C397-C401 ◽  
Author(s):  
H. M. Said ◽  
L. Polenzani ◽  
S. Khorchid ◽  
D. Hollander ◽  
R. Miledi
Keyword(s):  
Xenopus Laevis ◽  
Mammalian Cells ◽  
Xenopus Oocytes ◽  
Sulfhydryl Group ◽  
Maximum Velocity ◽  
Significant Inhibition ◽  
Metabolic Inhibitors ◽  
Xenopus Laevis Oocytes ◽  
Uptake System

The present study examined biotin uptake by Xenopus laevis oocytes in vitro. Uptake of low (0.03 microM) and high (10 microM) concentrations of biotin was linear with time for up to 4 h of incubation and occurred with little initial binding to oocytes. Uptake of biotin was dependent on extracellular Na+ concentration [Na+]o and was severely inhibited when Na+ was replaced by other monovalent cations [choline, tetraethylammonia, Li+, and tris(hydroxymethyl)aminomethane]. The initial rate of biotin uptake was saturable as a function of concentration with an apparent Michaelis constant of 3.9 +/- 0.5 microM and maximum velocity of 1,559 +/- 70 fmol.oocyte-1.h-1. Addition to the incubation medium of biotin structural analogues desthiobiotin and thioctic acid caused significant and concentration-dependent inhibition in the uptake of [3H]biotin. This inhibition was found to be competitive in nature with inhibition constant values of 9 and 17.5 microM. In contrast, neither the structural analogue biocytin nor biotin methyl ester (compounds in which the carboxyl group of the valeric acid moiety is blocked) showed any effect on the uptake of [3H]biotin. Biotin uptake was significantly blocked by the metabolic inhibitors dinitrophenol, cyanide, and azide and by incubation at 4 degrees C. Also, the sulfhydryl group blocker p-(chloromercuri)phenylsulfonate caused significant inhibition in biotin uptake. These results demonstrate that Xenopus oocytes possess an uptake system for biotin in its cell membrane that is Na+, energy, and temperature dependent. These characteristics of biotin uptake are similar to those reported in mammalian cells. It is suggested that Xenopus oocytes might be a useful in vitro model system to study the details of the mechanisms and regulation of biotin movement across biological membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The Organogermanium Compound THGP Suppresses Melanin Synthesis via Complex Formation with L-DOPA on Mushroom Tyrosinase and in B16 4A5 Melanoma Cells

2019 ◽  
Vol 20 (19) ◽  
pp. 4785
Author(s):  
Junya Azumi ◽  
Tomoya Takeda ◽  
Yasuhiro Shimada ◽  
Hisashi Aso ◽  
Takashi Nakamura
Keyword(s):  
Gene Expression ◽  
Kojic Acid ◽  
Biological Activities ◽  
Melanoma Cells ◽  
Tyrosinase Activity ◽  
Melanin Synthesis ◽  
Mushroom Tyrosinase ◽  
Melanin Production ◽  
Organogermanium Compound ◽  
Or Gene

The organogermanium compound 3-(trihydroxygermyl)propanoic acid (THGP) has various biological activities. We previously reported that THGP forms a complex with cis-diol structures. L-3,4-Dihydroxyphenylalanine (L-DOPA), a precursor of melanin, contains a cis-diol structure in its catechol skeleton, and excessive melanin production causes skin darkening and staining. Thus, the cosmetic field is investigating substances that suppress melanin production. In this study, we investigated whether THGP inhibits melanin synthesis via the formation of a complex with L-DOPA using mushroom tyrosinase and B16 4A5 melanoma cells. The ability of THGP to interact with L-DOPA was analyzed by 1H-NMR, and the influence of THGP and/or kojic acid on melanin synthesis was investigated. We also examined the effect of THGP on cytotoxicity, tyrosinase activity, and gene expression and found that THGP interacted with L-DOPA, a precursor of melanin with a cis-diol structure. The results also showed that THGP inhibited melanin synthesis, exerted a synergistic effect with kojic acid, and did not affect tyrosinase activity or gene expression. These results suggest that THGP is a useful substrate that functions as an inhibitor of melanogenesis and that its effect is enhanced by combination with kojic acid.

scholarly journals A New Phenolic Constituent From Carica papaya Flowers and Its Tyrosinase Inhibitory Activity

2019 ◽  
Vol 14 (7) ◽  
pp. 1934578X1985098
Author(s):  
Giang Thi Kim Lien ◽  
Do Thi Thuy Van ◽  
Dao Hung Cuong ◽  
Pham Hai Yen ◽  
Bui Huu Tai ◽  
...  
Keyword(s):  
Spectral Data ◽  
Inhibitory Activity ◽  
Carica Papaya ◽  
Kojic Acid ◽  
Positive Control ◽  
Natural Source ◽  
Tyrosinase Inhibitory Activity ◽  
Esi Ms ◽  
Phenolic Constituent

A new phenolic (caricapapayol, 1) and 8 known compounds (2-9) were isolated from the flowers of Carica papaya. Their structures were determined by analysis of HR-ESI-MS, NMR spectral data, and comparison with the literature. Among known compounds, compound 2 has not been reported from natural source. Compounds 1, 2, and 4 exhibited tyrosinase inhibitory activity with IC50 values of 14.3 ± 2.7, 25.5 ± 1.9, and 19.8 ± 3.0 µM, respectively, in comparison with positive control kojic acid IC50 11.3 ± 1.6 µM.

scholarly journals Potent Microbial and Tyrosinase Inhibitors from Stem Bark of Bauhinia Rufescens (Fabaceae)

2013 ◽  
Vol 8 (10) ◽  
pp. 1934578X1300801 ◽  
Author(s):  
Aminu Muhammad ◽  
Hasnah Mohd Sirat
Keyword(s):  
Kojic Acid ◽  
Stem Bark ◽  
Positive Control ◽  
Inhibition Assay ◽  
Bacterial Strains ◽  
Tyrosinase Inhibition ◽  
Fungal Strains ◽  
Inhibition Concentration ◽  
Tyrosinase Enzyme ◽  
Antimicrobial Assay

The stem bark extracts of Bauhinia rufescens Lam. (Fabaceae) yielded 6-methoxy-7-methyl-8-hydroxydibenz[ b,f]oxepin, α-amyrin acetate, β-sitosterol 3- O-β-D-xylopyranoside, 4-(2′-Hydroxyphenethyl)-5-methoxy-2-methylphenol, menisdaurin and sequoyitol. Their structures were determined using spectroscopic methods and comparisons with the literature data. For the antimicrobial assay Gram-positive and Gram-negative bacterial and fungal strains were tested, while the tyrosinase inhibition assay utilized L-DOPA as a substrate for the tyrosinase enzyme. 6-Methoxy-7-methyl-8-hydroxydibenz[ b,f]oxepin, α-amyrin acetate, β-sitosterol 3- O-β-D-xylopyranoside, menisdaurin and sequoyitol showed weak to moderate activities with minimum inhibition concentration (MIC) values in the range of 112.5–900 μg/mL against all bacterial strains, while the MIC values for the fungal strains were in the range of 28.1–450 μg/mL. In the tyrosinase inhibition assay, α-amyrin acetate was found to be moderately active against tyrosinase with an inhibition of 62% at 0.1 mg/mL. This activity was lower than that of the positive control, kojic acid (85%).

Phytochemicals and Tyrosinase Inhibitory Activity from Piper caninum and Piper magnibaccum

2019 ◽  
Vol 25 (4) ◽  
pp. 358-363
Author(s):  
Nur Athirah Hashim ◽  
Farediah Ahmad ◽  
Wan Mohd Nuzul Hakimi Wan Salleh ◽  
Shamsul Khamis
Keyword(s):  
Inhibitory Activity ◽  
Kojic Acid ◽  
Biological Effects ◽  
Positive Control ◽  
Aromatic Plants ◽  
Tyrosinase Inhibitory Activity ◽  
Potential Source ◽  
Phytochemical Constituents ◽  
Reported Data ◽  
Ethyl Acetate Extracts

Background: Piper species are aromatic plants used as spices in the kitchen, but their secondary metabolites have also shown biological effects on human health. In traditional medicine, Piper species have been used worldwide to treat several diseases such as urological problems, skin, liver and stomach ailments, for wound healing, and as antipyretic and anti-inflammatory agents. In the present study, we attempted to isolate the phytochemicals from Piper caninum and Piper magnibaccum and evaluate their tyrosinase inhibitory activity. Methods: Phytochemical constituents of the extracts were investigated using various chromatographic and spectroscopic methods. The structures of the isolated phytochemicals were established by analysis of their spectroscopic data, as compared to that of reported data. Tyrosinase inhibitory activity was also tested on the extracts and selected compounds using mushroom tyrosinase as the enzyme. Results: Fractionation and purification of the extracts of Piper caninum and Piper magni­baccum afforded nine known compounds which were cepharanone A (1), cepharadione A (2), aristolactam AII (3), 5,7-dimethoxyflavone (4), 24-methylenecycloartan-3-one (5), β-sitosterol (6), piperumbellactam A (7), 24S-ethylcholesta-5,22,25-trien-3β-ol (8) and stigmast-3,6-dione (9). Ethyl acetate extracts from leaves of P. magnibaccum gave the highest inhibition value at 48.35%, while the tested compounds displayed weak tyrosinase activity compared to the positive control, kojic acid. Conclusion: These phytochemical results suggested that the extracts could assist as a potential source of bioactive compounds. Further research is needed in which the extract could possibly be exploited for pharmaceutical use.

scholarly journals Different Proportions of Huangqi (Radix Astragali Mongolici) and Honghua (Flos Carthami) Injection onα-Glucosidase andα-Amylase Activities

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Hui Liao ◽  
Linda Banbury
Keyword(s):  
Amylase Activity ◽  
Positive Control ◽  
Significant Inhibition ◽  
Radix Astragali ◽  
Glucosidase Activity ◽  
Glucosidase Inhibitors ◽  
Flos Carthami ◽  
Simultaneous Inhibition ◽  
Amylase Inhibitors ◽  
Hydrolysis Of

Objective.To study the effect of different proportions of Huangqi (Radix Astragali Mongolici) and Honghua (Flos Carthami) injection onα-glucosidase andα-amylase activity simultaneously.Methods.The injections were prepared according to the standards of the China Food and Drug Administration. The assay for potentialα-glucosidase inhibitors was based on the hydrolysis of 4-methylumbelliferyl-α-D-glucopyranoside (4-MUG). Theα-amylase EnzChek assay kit was used to determine potentialα-amylase inhibitors. Acarbose was the positive control.Results.The half maximal (50%) inhibitory concentration (IC50) of acarbose againstα-glucosidase andα-amylase was (1.8±0.4)μg/mL and (227±32)μg/mL, respectively. Honghua showed significant inhibition ofα-glucosidase activity compared with Huangqi (P<0.01). Honghua inhibitedα-amylase activity, but Huangqi did not. IC50s forα-glucosidase inhibition by mixtures at 10 : 1, 5 : 1, and 2 : 1 were significantly lower than those at the 20 : 1 mixture (P<0.01).α-Amylase inhibition by the 2 : 1 mixture was significantly higher than that by the 20 : 1, 10 : 1, and 5 : 1 mixtures at 500 μg/mL and 1000 μg/mL (P<0.01), with 5 : 1 significantly higher than 20 : 1 and 10 : 1 at 1000 μg/mL (P<0.01).Conclusion.Honghua significantly inhibitedα-glucosidase activity compared with Huangqi (P<0.01). For simultaneous inhibition ofα-glucosidase andα-amylase activities, the mixtures at 2 : 1 and 5 : 1 exhibited significant effects compared with those at 20 : 1 (P<0.01).

Sign in / Sign up

Export Citation Format

Share Document