PURPOSE: We determined whether an extract from the bark of the tree Aspidosperma quebracho blanco, which is used as a prescription drug to treat erectile dysfunction in some countries, can bind to human penile alpha1 and alpha2-adrenoceptors, and cloned human alpha-adrenoceptor subtypes. MATERIALS AND METHODS: Competition binding studies were performed with alpha1 and alpha2-adrenoceptors with the extract and 4 subfractions prepared from it using [3H]prazosin (New England Nuclear, Dreieich, Germany) and [3H]RX 821002 (2-methoxy-idazoxam) (Amersham, Braunschweig, Germany) as the radioligands, respectively. RESULTS: In a concentration dependent manner the extract inhibited 2-methoxy-idazoxam binding to human penile alpha2-adrenoceptors. Somewhat less potently it inhibited [3H] prazosin binding to penile alpha1-adrenoceptors. The extract also inhibited binding to cloned alpha2-adrenoceptors more potently than to alpha1-adrenoceptors but did not discriminate among subtypes. Subfraction B was more potent than the others for all cloned alpha1-adrenoceptor subtypes and much more potent at all penile and all cloned alpha2-adrenoceptor subtypes. This fraction largely contained yohimbine, whereas the other fractions were devoid of yohimbine. Based on yohimbine competition binding experiments with penile and cloned alpha1 and alpha2-adrenoceptors, it appears that the inhibitory effects of the abstract and its subfractions can largely be explained by its yohimbine content. CONCLUSIONS: An alpha-adrenoceptor mediated component of the pro-erectile effects of Aspidosperma quebracho blanco bark extract may predominantly be caused by its yohimbine content. The alpha-adrenoceptor independent, pro-erectile effects of the extract could not be determined from this study.
PURPOSE: We determined whether an extract from the bark of the tree Aspidosperma quebracho blanco, which is used as a prescription drug to treat erectile dysfunction in some countries, can bind to human penile alpha1 and alpha2-adrenoceptors, and cloned human alpha-adrenoceptor subtypes. MATERIALS AND METHODS: Competition binding studies were performed with alpha1 and alpha2-adrenoceptors with the extract and 4 subfractions prepared from it using [3H]prazosin (New England Nuclear, Dreieich, Germany) and [3H]RX 821002 (2-methoxy-idazoxam) (Amersham, Braunschweig, Germany) as the radioligands, respectively. RESULTS: In a concentration dependent manner the extract inhibited 2-methoxy-idazoxam binding to human penile alpha2-adrenoceptors. Somewhat less potently it inhibited [3H] prazosin binding to penile alpha1-adrenoceptors. The extract also inhibited binding to cloned alpha2-adrenoceptors more potently than to alpha1-adrenoceptors but did not discriminate among subtypes. Subfraction B was more potent than the others for all cloned alpha1-adrenoceptor subtypes and much more potent at all penile and all cloned alpha2-adrenoceptor subtypes. This fraction largely contained yohimbine, whereas the other fractions were devoid of yohimbine. Based on yohimbine competition binding experiments with penile and cloned alpha1 and alpha2-adrenoceptors, it appears that the inhibitory effects of the abstract and its subfractions can largely be explained by its yohimbine content. CONCLUSIONS: An alpha-adrenoceptor mediated component of the pro-erectile effects of Aspidosperma quebracho blanco bark extract may predominantly be caused by its yohimbine content. The alpha-adrenoceptor independent, pro-erectile effects of the extract could not be determined from this study.
Authors: Iara Leão Luna de Souza; Bárbara Cavalcanti Barros; Elba Dos Santos Ferreira; Fernando Ramos Queiroga; Luiz Henrique César Vasconcelos; Lydiane de Lima Tavares Toscano; Alexandre Sérgio Silva; Patrícia Mirella da Silva; Fabiana de Andrade Cavalcante; Bagnólia Araújo da Silva Journal: Mar Drugs Date: 2022-07-22 Impact factor: 6.085