The present invention discloses therapeutic natural products, in particular plant extracts effective in treating and preventing urinary tract disorders, and method for obtaining said extracts. In particular, the present invention discloses a water-soluble alcoholic extract of Opuntia ficus-indica flower (NABIA extract), a component thereof (NABIA fraction) or any mixture of components thereof, which is substantially free of non water-soluble residues, and exhibits an effective alpha-1-adrenergic receptor blocking activity. Further are disclosed methods of preparing this extract and methods of inhibiting alpha-1-adrenergic receptors and/or 5-alpha-reductase, as well as of treating medical conditions associated therewith, such as urinary tract disorders.