RESUMO
The oxidation of 4-t-butylcatechol catalyzed by mushroom tyrosinase was inhibited by 4-bromobenzaldehyde, 4-chlorobenzaldehyde, 4-fluorobenzaldehyde, 4-cyanobenzaldehyde, and 4-nitrobenzaldehyde with 50% inhibitory concentrations of 114 µM, 175 µM, 387 µM, 822 µM, and 1846 µM, respectively. The inhibition kinetics were analyzed by Dixon plots, which indicated that a series of 4-hallogenated benzaldehydes acted as partial noncompetitive inhibitors in the same manner as benzaldehyde. Although ß values were decreased with an increase of the tyrosinase inhibitory activity, full inhibition could not be observed. In contrast, 4-cyanobenzaldehyde and 4-nitrobenzaldehyde acted as mixed and noncompetitive inhibitors, respectively. Full inhibition was particularly represented by 4-nitrobenzaldehyde. According to a previous report, 4-alkylbenzaldehyde and 4-alkoxybenzaldehyde with a bulky substituent acted as full inhibitors. Those results suggested that the steric factor at the 4-position triggered the alternation between partial or full tyrosinase inhibition irrespective of electronic or hydrophobic effects.
Assuntos
Benzaldeídos/química , Desenho de Fármacos , Monofenol Mono-Oxigenase/antagonistas & inibidores , Agaricales/química , Benzaldeídos/farmacologia , Catálise , Avaliação Pré-Clínica de Medicamentos , Elétrons , Inibidores Enzimáticos/farmacologia , Concentração Inibidora 50 , Cinética , Monofenol Mono-Oxigenase/química , OxirreduçãoRESUMO
Sonnerphenolic C (3), which was predicted in a redox product of epirhododendrin (1) isolated from Acer nikoense, was synthesized for the first time via the epimeric separation of benzylidene acetal intermediates as a key step. From a similar synthetic route, 1 was obtained concisely. As a result of their antioxidative evaluation, only 3 revealed potent activity. The redox transformation of 1 into 3 was achieved in the presence of tyrosinase and vitamin C. Moreover, 3 was identified in the decoction of A. nikoense by HPLC analysis with the effective use of synthesized 3. Thus, a novel naturally occurring antioxidant 3 was developed through the sequential flow including redox prediction, chemical synthesis, evaluation of the activity, and identification as the natural product.
Assuntos
Acer/química , Antioxidantes/síntese química , Antioxidantes/farmacologia , Catecóis/síntese química , Catecóis/farmacologia , Glucosídeos/síntese química , Glucosídeos/farmacologia , Extratos Vegetais/química , Antioxidantes/isolamento & purificação , Ácido Ascórbico/farmacologia , Compostos de Bifenilo/química , Catecóis/isolamento & purificação , Glucosídeos/isolamento & purificação , Oxirredução , Picratos/químicaRESUMO
On the basis of antibacterial anacardic acids, 6-pentadecenylsalicylic acids, isolated from the cashew apple, Anacardium occidentale L. (Anacardiaceae), a series of 6-alk(en)ylsalicylic acids were synthesized and tested for their antibacterial activity against Streptococcus mutans ATCC 25175. Among them, 6-(4',8'-dimethylnonyl)salicylic acid was found to exhibit the most potent antibacterial activity against this cariogenic bacterium with the minimum inhibition concentration (MIC) of 0.78 microg/ml.
Assuntos
Ácidos Anacárdicos/síntese química , Ácidos Anacárdicos/farmacologia , Cárie Dentária/prevenção & controle , Desenho de Fármacos , Antibacterianos/síntese química , Antibacterianos/farmacologia , Avaliação Pré-Clínica de MedicamentosRESUMO
Two novel limonoids, musidunin (1) and musiduol (2), were isolated from a methanol extract of Croton jatrophoides by bioassay-guided fractionation. Their structures were established by extensive NMR experiments. Interestingly, A,B-seco limonoid 1 contains a unique acetal annulation of A, A', and B' rings. Both limonoids exhibited antifeedant activities against two pests, Pectinophora gossypiella and Spodoptera frugiperda.
Assuntos
Croton/química , Comportamento Alimentar/efeitos dos fármacos , Lepidópteros/efeitos dos fármacos , Limoninas/isolamento & purificação , Plantas Medicinais/química , Animais , Quênia , Larva/efeitos dos fármacos , Limoninas/química , Limoninas/farmacologia , Estrutura Molecular , Controle Biológico de VetoresRESUMO
This is the first report for secondary metabolites in an African medicinal plant, Pachyelasma tessmannii (Leguminosae). Four novel saponins, pachyelasides A-D, were isolated from the methanol extract of the root bark by using recycling HPLC. These compounds showed molluscicidal activity (LD(50) < or =8.0 mug/mL) against the South American snail, Biomphalaria glabratus. The structures were determined on the basis of extensive nuclear magnetic resonance spectroscopic and matrix-assisted laser desorption/ionization time-of-flight mass spectrometric studies.
Assuntos
Biomphalaria/efeitos dos fármacos , Fabaceae/química , Saponinas/isolamento & purificação , Saponinas/farmacologia , Triterpenos/isolamento & purificação , Triterpenos/farmacologia , Animais , Extratos Vegetais/química , Raízes de Plantas/química , Saponinas/química , Triterpenos/químicaRESUMO
Three new A-seco limonoids, zumketol (1), zumsenin (2), and zumsenol (3), were isolated from a methanol extract of Croton jatrophoides by bioassay-guided fractionation, and their structures were determined by NMR analysis. The alpha-ketol 1 may be biosynthesized via the intramolecular acyloin condensation of a dicarboxylate intermediate.
Assuntos
Croton/química , Comportamento Alimentar/efeitos dos fármacos , Lepidópteros/efeitos dos fármacos , Limoninas/isolamento & purificação , Plantas Medicinais/química , Animais , Quênia , Larva/efeitos dos fármacos , Limoninas/química , Limoninas/farmacologia , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Casca de Planta/químicaRESUMO
Arbutin, hydroquinone-O-beta-D-glucopyranoside (1) was found to inhibit the oxidation of l-tyrosine (monophenolase activity) catalyzed by mushroom tyrosinase. However, arbutin itself was oxidized as a monophenol substrate at an extremely slow rate, and this oxidation was accelerated as soon as catalytic amounts (0.01 mM) of l-3,4-dihydroxyphenylalanine (L-DOPA) became available as a cofactor. The result observed was supported by monitoring oxygen consumption. The depigmenting mechanism of arbutin previously reported is supportable if a cofactor is not available in the melanocytes. The combination with L-ascorbic acid is a useful application, particularly when oxygen is limited.
Assuntos
Agaricales , Arbutina/farmacologia , Melanócitos/efeitos dos fármacos , Monofenol Mono-Oxigenase/efeitos dos fármacos , Fitoterapia , Pigmentação/efeitos dos fármacos , Arbutina/química , Humanos , OxirreduçãoRESUMO
Two novel A-seco limonoids, dumnin and dumsenin, were isolated from the methanolic extract of Croton jatrophoides by bioassay-guided fractionation, and the structures were determined by nuclear magnetic resonance, circular dichroism, and mass spectrometry experiments. These compounds showed potent antifeedant activity (PC(50) Assuntos
Croton/química
, Inseticidas/química
, Limoninas/química
, Animais
, Dicroísmo Circular
, Inseticidas/isolamento & purificação
, Larva
, Limoninas/isolamento & purificação
, Espectroscopia de Ressonância Magnética
, Espectrometria de Massas
, Metanol
, Estrutura Molecular
, Mariposas
, Extratos Vegetais/química
, Spodoptera
RESUMO
As a defense mechanism of the leaves of Rhus javanica (Anacardiaceae) against the aphid Melaphis chinensis (Aphididae) attack, tannic acid is rapidly accumulated and forms galls along the midrib of the leaves resulting in a unique natural medicine Gallae Rhois. Tannic acid was found to inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by tyrosinase (EC 1.14.18.1) with an IC50 of 22 microM. The aphid would detoxify the ingested toxic tannic acid to relatively nontoxic gallic acid, whereas the non-adapted pink bollworm Pectinophora gossypiella larvae are sensitive to the ingested tannic acid.
Assuntos
Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Ácido Gálico/química , Inseticidas/química , Monofenol Mono-Oxigenase/antagonistas & inibidores , Folhas de Planta/química , Rhus/química , Agaricales/enzimologia , Animais , Inibidores Enzimáticos/isolamento & purificação , Sequestradores de Radicais Livres , Ácido Gálico/isolamento & purificação , Ácido Gálico/farmacologia , Insetos , Inseticidas/isolamento & purificação , Inseticidas/toxicidade , Plantas Medicinais/químicaRESUMO
A novel A-seco limonoid was isolated from methanolic extract of Croton jatrophoides and designated as zumsin. This compound showed potent antifeedant activity against two lepidopteran larvae, pink bollworm, Pectinophora gossypiella (PC(50) = 1 microg/cm(2), PC(95) = 8 microg/cm(2)), and fall armyworm, Spodoptera frugiperda (PC(50) = 2 microg/cm(2), PC(95) = 16 microg/cm(2)). The structure of zumsin was determined as 1 using a variety of spectroscopic methods including nuclear magnetic resonance, mass spectrometry, and circular dichroism. The structure consists of an A'-B trans-fused ring while dumsin (2), a constituent of the same source, maintains an A'-B cis-fused ring, and suggests two unique biosynthetic processes after A ring oxidative expansion.