RESUMO
To clarify the suppression of postprandial blood glucose rise via alpha-glucosidase (AGH) inhibitory action by natural compounds, propolis was examined in this study. A single oral administration of propolis extract (50% methanol fraction on XAD-2 column chromatography) in Sprague-Dawley rats demonstrated a potent antihyperglycemic effect with the significant AUC(0-120 min) reduction of 38% at a dose of 20 mg/kg compared to that of controls. Among the active compounds isolated from the fraction, 3,4,5-tri-caffeoylquinic acid was found to be a prominent candidate that exerts the effect and shows a strong maltase-specific inhibition with an IC(50) value of 24 microM. In addition, the noncompetitive inhibition power apparently increased with the number of caffeoyl groups bound to quinic acid.
Assuntos
Hipoglicemiantes/farmacologia , Própole , Ácido Quínico/análogos & derivados , Administração Oral , Animais , Área Sob a Curva , Glicemia/efeitos dos fármacos , Brasil , Hipoglicemiantes/química , Masculino , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Folhas de Planta/química , Própole/química , Ácido Quínico/química , Ácido Quínico/farmacologia , Ratos , Ratos Sprague-Dawley , Solubilidade , Fatores de Tempo , ÁguaRESUMO
Some Sri Lanka plant stuffs were examined regarding in vitro and in vivo alpha-glucosidase (AGH) inhibitory actions. According to the results, water extracts and methanol extracts of dried fruits of Nelli (Phylanthus embelica), methanol extracts of dried flowers of Ranawara (Cassia auriculata), and water extracts of latex of Gammalu (Pterocarpus marsupium) were found to have a potential AGH inhibitory activity. In particular, Ranawara methanol extract showed the strongest AGH inhibitory activity in vitro preferably on maltase giving an IC(50) value of 0.023 mg/mL and inhibited the maltase activity competitively. As a result of single oral administration of Ranawara (C. auriculata) methanol extract in Sprague-Dawley rats, a significant and potent lowering of blood glycemic response toward maltose ingestion was observed at 30 min after dosing of 5 mg/kg, thus, concurrently suppressed insulin activity. The ED(50) of the extract (4.9 mg/kg) clearly indicated that the antihyperglycemic effect was as potent as that of therapeutic drug, acarbose (ED(50) 3.1 mg/kg).
Assuntos
Acarbose/farmacologia , Cassia/química , Inibidores Enzimáticos/farmacologia , Inibidores de Glicosídeo Hidrolases , Hipoglicemiantes/farmacologia , Extratos Vegetais/farmacologia , Animais , Glicemia/metabolismo , Relação Dose-Resposta a Droga , Cinética , Masculino , Ratos , Ratos Sprague-Dawley , Sri LankaRESUMO
The quantification of glucose by using a multi-channel dissolved oxygen (DO) meter (DOX96) with immobilized glucose oxidase (GOD) and mutarotase (MUT) was performed. An evaluation of the inhibitory activities for alpha-glucosidase (AGH) by modifying our batch-type pseudo-in vivo assay system [Oki et al.; Biol Pharm. Bull., 2000, 232, 1084] was also performed using a DOX96. When 45 U/well GOD and 18.75 U/well MUT were immobilized on the surface of a gelatin membrane on the electrodes, the response shown by the decrease percent of DO (%) obtained with 8 electrode wells in the same row was linear with the glucose concentration up to 3.3 mM and a correlation coefficient larger than 0.9. To estimate the AGH inhibitory activity, AGH-immobilized Sepharose supports in the well of a silent screen plate were used. The IC50 values of acarbose and 1-deoxynojirimycin, a medicinal inhibitor for diabetes, were 0.70 +/- 0.08 microM and 0.40 +/- 0.13 microM, respectively, and coincided well with those by a pseudo-in vivo assay.