Natural neuroactive compounds isolated from medicinal plants

MARIEL MARDER

Academia de Ciências de Rio de Janeiro, Brazil

Conferencia; 5th Regional Conference of Young Scientists of TWAS-ROLAC “Galileu e Darwin: luzes da ciência sobre onde estamos e o que somos” Reunião Magna; 2009

NATURAL NEUROACTIVE COMPOUNDS ISOLATED FROM MEDICINAL PLANTS Mariel Marder Instituto de Química y Fisicoquímica Biológicas (IQUIFIB, UBA-CONICET), Facultad de Farmacia y Bioquímica, UBA. Junín 956, Buenos Aires, Argentina. e-mail: mmarder@qb.ffyb.uba.ar Herbs have been highly valued and used regularly for thousands of years by people all over the world as the medicine of the masses. Medicinal plants have been used to treat such psychotropic and behavioral conditions as anxiety, depression, seizures, poor memory, dementia, insomnia, and drug intoxication. Plants contain many complex substances that may account for the variety of the claimed medical uses. There is limited information regarding herb-drug and herb-herb interactions and their mechanisms, metabolism and excretion are largely unstudied. Also, herbal products are generally unregulated and often health claims are unsubstantiated or sometimes exaggerated. It must not be assumed that since an herb has been used for thousands of years the herb is necessarily safe and truly effective for its claimed indication. In order to investigate the properties of an herb, or of its active isolated compounds, we use animal models of anxiety, sedation, sleep and pain in rodents. Our studies deals with plants possessing central nervous system effects, such as Passiflora species (Passion flower), Matricaria recutita L. (Chamomile), Tilia species (Linden), Salvia species (Sage) and Valeriana species. We also isolate and identify their active constituents and investigate their mechanism of action. An animal model is a non-human animal that has a disease or injury that is similar to a human condition. These test conditions are often termed as animal models of disease. The use of animal models allows researchers to investigate disease states in ways which would be inaccessible in a human patient, performing procedures on the non-human animal that imply a level of harm that would not be considered ethical to inflict on a human. In turn to serve as a useful model, a modeled disease must be similar in etiology (mechanism of cause) and function to the human equivalent. Animal models are used to learn more about a disease, its diagnosis and its treatment. Behavioral analogues of anxiety or pain in laboratory animals can be used to screen and test new drugs for the treatment of these conditions in humans. A search for novel pharmacotherapy from medicinal plants for psychiatric illnesses has progressed significantly in the last twenty years. This is reflected in the large number of herbal preparations for which psychotherapeutic potential has been evaluated in a variety of animal models. A considerable number of herbal constituents whose behavioral effects and pharmacological actions have been well characterized may be good candidates for further investigations that may ultimately result in clinical use. Studies from our laboratory have shown that flavonoids, present in tranquillizing plants are responsible for most of their pharmacological properties, anxiolytic and sedative effects, which are probably exerted by a similar mechanism to that of benzodiazepines, since the active flavones are good ligands for the benzodiazepine binding site of the GABAA receptor in the brain. However, it was subsequently found that flavonoid glycosides, also present in tranquillizing plants, e.g. valeriana, although exerting central nervous system depressant effects, do not involve the GABAA receptor and the participation of the opioid receptors in their depressant activities was recently demonstrated for the most active derivative, hesperidin.