RESUMO
A dichloromethane extract from leaves of Searsia pyroides potentiated gamma aminobutyric acid-induced chloride currents by 171.8 ± 54% when tested at 100 µg/mL in Xenopus oocytes transiently expressing gamma aminobutyric acid type A receptors composed of α1ß2γ2s subunits. In zebrafish larvae, the extract significantly lowered pentylenetetrazol-provoked locomotion when tested at 4 µg/mL. Active compounds of the extract were tracked with the aid of HPLC-based activity profiling utilizing a previously validated zebrafish larval locomotor activity assay. From two active HPLC fractions, compounds 1â-â3 were isolated. Structurally related compounds 4â-â6 were purified from a later eluting inactive HPLC fraction. With the aid of 1H and 13C NMR and high-resolution mass spectrometry, compounds 1â-â6 were identified as analogues of anacardic acid. Compounds 1â-â3 led to a concentration-dependent decrease of pentylenetetrazol-provoked locomotion in the zebrafish larvae model, while 4â-â6 were inactive. Compounds 1â-â3 enhanced gamma aminobutyric acid-induced chloride currents in Xenopus oocytes in a concentration-dependent manner, while 4â-â6 only showed marginal enhancements of gamma aminobutyric acid-induced chloride currents. Compounds 2, 3, and 5 have not been reported previously.
Assuntos
Anacardiaceae/química , Ácidos Anacárdicos/farmacologia , GABAérgicos/farmacologia , Extratos Vegetais/farmacologia , Receptores de GABA-A/metabolismo , Ácido gama-Aminobutírico/metabolismo , Ácidos Anacárdicos/química , Ácidos Anacárdicos/isolamento & purificação , Animais , Bioensaio , Cloretos , Cromatografia Líquida de Alta Pressão , GABAérgicos/química , GABAérgicos/isolamento & purificação , Larva , Locomoção/efeitos dos fármacos , Cloreto de Metileno , Oócitos , Pentilenotetrazol , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Folhas de Planta/química , Xenopus laevis , Peixe-ZebraRESUMO
The hERG channel is an important antitarget in safety pharmacology. Several drugs have been withdrawn from the market or received severe usage restrictions because of hERG-related cardiotoxicity. In a screening of medicinal plants for hERG channel inhibition using a two-microelectrode voltage clamp assay with Xenopus laevis oocytes, a dichloromethane extract of the roots of Gnidia polycephala reduced the peak tail hERG current by 58.8 ± 13.4% (n = 3) at a concentration of 100 µg/mL. By means of HPLC-based activity profiling daphnane-type diterpenoid orthoesters (DDOs) 1, 4, and 5 were identified as the active compounds [55.4 ± 7.0% (n = 4), 42.5 ± 16.0% (n = 3), and 51.3 ± 9.4% (n = 4), respectively, at 100 µM]. In a detailed phytochemical profiling of the active extract, 16 compounds were isolated and characterized, including two 2-phenylpyranones (15 and 16) with an unprecedented tetrahydro-4H-5,8-epoxypyrano[2,3-d]oxepin-4-one skeleton, two new DDOs (3 and 4), two new guaiane sesquiterpenoids (11 and 12), and 10 known compounds (1, 2, 5-10, 13, and 14). Structure elucidation was achieved by extensive spectroscopic analysis (1D and 2D NMR, HRMS, and electronic circular dichroism), computational methods, and X-ray crystallography.
Assuntos
Benzoxepinas/isolamento & purificação , Benzoxepinas/farmacologia , Diterpenos/isolamento & purificação , Diterpenos/farmacologia , Canais de Potássio Éter-A-Go-Go/antagonistas & inibidores , Thymelaeaceae/química , Animais , Benzoxepinas/química , Cromatografia Líquida de Alta Pressão , Cristalografia por Raios X , Diterpenos/química , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Oócitos/efeitos dos fármacos , África do Sul , XenopusRESUMO
Five labdane (1-5), an isolabdane (6), and five clerodane diterpenoids (7-11), were isolated from seeds, husks, and leaves of Colophospermum mopane. Compounds 1-3 and 6-9 are new, and their structures were elucidated by means of physical data analysis (1D and 2D NMR, HRESIMS). The absolute configurations of 1, 7, and 10 were determined by single-crystal X-ray diffraction with Cu Kα radiation. For compounds 2 and 6, the absolute configurations were established by the modified Mosher's method and corroborated by comparison of experimental and calculated electronic circular dichroism spectra of their 3-p-bromobenzoate derivatives. The crude extracts and compounds were evaluated for antimicrobial activity. The leaf extract was the most active against Staphylococcus aureus (125 µg/mL). Compound 11 showed the best inhibitory activity, with minimum inhibitory values of 15.6 µg/mL against Escherichia coli and Staphylococcus aureus and 31.3 µg/mL against Enterococcus faecalis.
Assuntos
Antibacterianos/isolamento & purificação , Diterpenos Clerodânicos/isolamento & purificação , Diterpenos/isolamento & purificação , Fabaceae/química , Antibacterianos/química , Antibacterianos/farmacologia , Diterpenos/química , Diterpenos/farmacologia , Diterpenos Clerodânicos/química , Diterpenos Clerodânicos/farmacologia , Enterococcus faecalis/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Klebsiella pneumoniae/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Folhas de Planta/química , Sementes/química , África do Sul , Staphylococcus aureus/efeitos dos fármacos , EstereoisomerismoRESUMO
The human ether-a-go-go-related gene channel is a voltage-activated K(+) channel involved in cardiac action potential. Its inhibition can lead to QT prolongation, and eventually to potentially fatal arrhythmia. Therefore, it is considered a primary antitarget in safety pharmacology. To assess the risk of human ether-a-go-go-related gene channel inhibition by medicinal plants, 700 extracts from different parts of 142 medicinal plants collected in Southern Africa were screened on Xenopus laevis oocytes. A CH2Cl2 extract from the stems and leaves of Galenia africana (Aizoaceae) reduced the peak tail human ether-a-go-go-related gene current by 50.4 ± 5.5â% (n = 3) at a concentration of 100 µg/mL. By means of high-performance liquid chromatography-based activity profiling, nine flavonoids were identified in the active time windows. However, the human ether-a-go-go-related gene channel inhibition of isolated compounds was less pronounced than that of extract and active microfractions (human ether-a-go-go-related gene inhibition between 10.1 ± 5 and 14.1 ± 1.6 at 100 µM). The two major constituents, 7,8-methylenedioxyflavone (1) and 7,8-dimethoxyflavone (13), were quantified (4.3â% and 9.4â%, respectively, in the extract). Further human ether-a-go-go-related gene inhibition tests for compounds 1 and 13 at 300 µM showed a concentration-dependent inhibitory activity (33.2 ± 12.4 and 30.0 ± 7.4, respectively). In a detailed phytochemical profiling of the active extract, a total of 20 phenolic compounds, including six new natural products, were isolated and identified.