Flavonoid compounds isolated from Tibetan herbs, binding to GABAA receptor with anxiolytic property.

ETHNOPHARMACOLOGICAL RELEVANCE: Previously, the phytochemical constituents of Biebersteinia heterostemon Maxim (BHM) and Arenaria kansuensis Maxim (AKM) were studied and the evaluation of anxiolytic effect based on their extracts was also investigated. The two traditional Tibetan herbs, BHM and AKM, have been widely used in Qinghai-Tibet Plateau for cardiopulmonary disorders and neuropsychiatric diseases. The anxiolytic activities of a number of agents mediated by α2/3-containing GABAA receptors (GABAARs) have been demonstrated through the genetic and pharmacological studies. Flavonoids, such as flavones and flavanols, are a class of ligands that act at GABAARs and exhibit anxiolytic effects in vivo. Here, the flavonoids are the predominant constituents isolated from BHM and AKM. And our purpose is to investigate structure-activity relationships of the flavonoid compounds with binding to BZ-S of GABAAR complexes, and to search for anxiolytic constituents that lack undesirable-effects such as sedation and myorelaxation. MATERIALS AND METHODS: The flavonoid constituents were separated and purified through the repeatedly silica gel or/and C18 column chromatography. The affinities of the compounds for BZ-S of GABAARs were detected by the radioreceptor binding assay with bovine cerebellum membranes, in which the different recombinant subunits-containing GABAARs were expressed in HEK 293T cells. The behavior tests, including elevated plus maze, locomotor activity, holeboard, rotarod and horizontal wire, were used to determine and evaluate the anxiolytic, sedative, and myorelaxant effects of these flavonoids. RESULTS: Eleven total flavonoid compounds were obtained from the Tibetan herbs (BHM and AKM). The flavones with 6-and/or 8-OMe possessed the most potent binding affinity to GABAARs, which were based on the result of structure-activity relationships analysis. Demethoxysudachitin (DMS, Ki = 0.59 µM), a flavone that binds to recombinant α1-3/5 subunit-containing GABAARs, was isolated from BHM, and exhibited high anxiolytic activity, without inducing sedation and myorelaxation. Moreover, the anxiolytic effect of DMS was antagonized by flumazenil, suggesting that a mode of action was mediated via the BZ-S of GABAARs. CONCLUSIONS: This present study indicated that the flavones, especially DMS, are novel GABAAR ligands and therapeutic potential candidates for anxiety.

Synadenium umbellatum: citotoxicidade e danos ao DNA de células da medula óssea de camundongos / Synadenium umbellatum: cytotoxicity and DNA damage to bone marrow cells from mice

No presente estudo investigamos o potencial citotóxico e mutagênico, in vitro e in vivo, respectivamente, do extrato etanólico de Synadenium umbellatum (EESU) sobre células da medula óssea de camundongos. A citotoxicidade in vitro foi avaliada por meio da exposição de células da medula óssea de animais normais a diferentes concentrações (40-0,312 mg/mL) do EESU, por 12, 24 ou 48 h, utilizando os testes de redução do MTT e o de exclusão do azul de tripano. O ensaio de micronúcleo foi realizado para investigar potenciais efeitos mutagênicos do EESU (10, 25 ou 50 mg/kg/dia) sobre a medula óssea de camundongos. Os animais foram expostos a uma única dose, por via oral, e 24 h após à exposição, sacrificados para realização do estudo (n=5/grupo). Os resultados obtidos demonstraram que o EESU possui potencial efeito citotóxico e mutagênico, de forma dose-dependente, sobre as células da medula óssea de camundongos, in vitro e in vivo, respectivamente. Maiores estudos são necessários para expandir o conhecimento acerca do potencial toxicológico/farmacológico do EESU.

In the present study we investigated, in vitro and in vivo, the cytotoxic and mutagenic potential of the Synadenium umbellatum ethanolic extract (SUEE) on the bone marrow cells of mice. In vitro cytotoxicity was assayed incubating bone marrow cells with different concentrations (40-0.312 mg/mL) of SUEE for 12, 24 or 48 h using the MTT tetrazolium reduction test and the trypan blue exclusion test. The micronuclei assay was performed to determine mutagenic effects of mice orally exposed to different doses of SUEE (10, 25 or 50 mg/kg/day) in 24 h. Our results demonstrated that SUEE has, in a dose-dependent manner, potential cytotoxic and mutagenic effects on the bone marrow cells of mice. Further studies are needed to expand the knowledge of the toxicological/pharmacological potential of the SUEE.